2/2/2016CBSE,class 12th,Physics practical file readings CBSE,class 12th,Physics practical file readings Hello! friends, got no time or no friends to borrow physics practical file reading and you need it badly right now : here is your solution: The return of my doomed work. I deleted my post by accident. But worry not friends. I recovered the lost copy of this blog and it is back to help you again. School is for enjoyment and sometimes we tend to left out few of the practicals. That is not a problem anymore. Before the submission of my practical file during the board exams. I knew that some scary looking teacher would just tear the file apart so that it cannot be used again. Physics file was the most difficult to maintain, all the reading and so much calculation. I thought in the day of my desolation when no one would share the file or they themselves have not completed it or maybe have done the whole practical wrong, interred a sense of Board Exam in my bones. Most of the practicals screenshot have been listed below with exact numbering. If you find anything missing or above your head, do post some comments as there are many others who visit this site and these might be able to help you out of this muck. EXP1> TO DETERMINE THE RESISTANCE PER CM OF A GIVEN WIRE BY PLOTTING A GRAPH OF POTENTIAL DIFFERENCE VERSUS CURRENT Materials Required: A Resistance wire, voltmeter, ammeter, battery, rheostat, meter scale, one way key, connecting wires etc. Theory: If I be the current flowing through a conductor & V be the potential difference across its ends, then according to Ohm’s law V∝I or V = RI Where, R is the constant of proportionality. It is known as resistance of the conductor. V/I=R R depends upon the nature of material, temperature & dimensions of the conductor. http://12tphysicspracticalfilereadings.blogspot.in/ 1/45 2/2/2016 http://12tphysicspracticalfilereadings.blogspot.in/ CBSE,class 12th,Physics practical file readings 2/45 2/2/2016 CBSE,class 12th,Physics practical file readings Procedure: 1. Clean the ends of the connecting wires with the help of sand paper in order to remove any insulating coating on them. 2. Connect various components resistance, rheostat, battery, key, voltmeter and ammeter 3. Note whether pointers in milliammeter and voltmeter coincide with the zero mark on the measuring scale. If it is not so, adjust the pointer to coincide with the zero mark by adjusting the screw provided near the base of the needle using a screw driver. 4. Note the range and least count of the given voltmeter and milliammeter. 5. Insert the key K and slide the rheostat contact to one of its extreme ends, so that current passing through the resistance wire is minimum. 6. Note the milliammeter and voltmeter readings. 7. Remove the key K and allow the wire to cool, if heated. Again insert the key. Shift the rheostat contact slightly to increase the applied voltage. Note the milliammeter and voltmeter reading. 8. Repeat step 7 for four different settings of the rheostat. Record your observations in a tabular form. OBSERVATIONS: 1. Range of ammeter = 0 ... mA to ...mA 2. Least count of ammeter = ... mA 3. Range of voltmeter = 0 ... V to ...V 4. Least count of voltmeter = ...V http://12tphysicspracticalfilereadings.blogspot.in/ 3/45 2/2/2016 CBSE,class 12th,Physics practical file readings 5. Least count of meter scale = ... m 6. Length of the given wire, l = ...m RESULT: 1. The potential difference across the given wire varies linearly with the current. 2. The resistance per unit length of the wire is (R ± ΔR) = (... ... Ωm1). EXP2> TO DETERMINE RESISTANCE OF GALVANOMETER BY HALF DEFLECTION METHOD AND TO FIND ITS FIGURE OF MERIT. MATERIAL REQUIRED: A moving coil galvanometer, a battery or a battery eliminator (0 6 V), one resistance box (RBOX 1) of range 010kΩ, one resistance box(RBOX 2) of range 0200Ω, 2 one way keys, voltmeter, connecting wires and a piece of sand paper. Theory: Galvanometer is a sensitive device used to detect very low current. Its working is based on the principle that a coil placed in a uniform magnetic field experiences a torque when an electric current is set up in it. The deflection of the coil is determined by a pointer attached to it, moving on the scale. When a coil carrying current I is placed in a radial magnetic field, the coil experiences a deflection θ which is related to I as I=kθ where k is a constant of proportionality and is termed as figure of merit of the galvanometer. http://12tphysicspracticalfilereadings.blogspot.in/ 4/45 in/ CBSE.Physics practical file readings 5/45 .2/2/2016 http://12tphysicspracticalfilereadings.class 12th.blogspot. blogspot. Insert the key K2 and keep R fixed. R and deflection θ. 3.2/2/2016 CBSE.Physics practical file readings Procedure: 1. Record the values of resistance. Clean the connecting wires with sand paper and make neat and tight connections as per the circuit diagram 2.in/ 6/45 . Adjust the value of shunt resistance S to get the deflection in http://12tphysicspracticalfilereadings. Adjust the resistance R from this resistance box to get full scale deflection on the galvanometer dial. remove 5 kΩ key and then close the key K1. From the high resistance box (RBOX 1) (110 kΩ).class 12th. Calculate the galvanometer resistance G and figure of merit k of galvanometer using Equations. Figure of merit of galvanometer. Remove plug K2 after noting down the value of shunt resistance... http://12tphysicspracticalfilereadings. S.blogspot.V Number of divisions on full scale of galvanometer = . 4. two unknown resistance wires. battery.class 12th. one way key. galvanometer. Note down S. S..in/ 7/45 . jockey... Materials Required: Meter bridge. and connecting wires.. a resistance box. 5.2/2/2016 CBSE.. the known resistance. Ω 2. Resistance of galvanometer by half deflection method. k = . G = .ampere/division EXP3> TO VERIFY LAWS OF COMBINATION OF RESISTOR USING A METER BRIDGE.. Take five sets of observations by repeating steps 2 and 3 so that θ is even number of divisions and record the observations for R. RESULT: 1... OBSERVATIONS: Emf of the battery E =.Physics practical file readings the galvanometer which is exactly half of θ.. θ and 2 in tabular form. Theory: The effective resistance Xs of the combination of two resistors when connected in series can be calculated by : Xs = X1+ X2(i) The resistance (X ) of a resistor is given by: (ii) Where ‘l’ is the balancing length and R. blogspot.Physics practical file readings 8/45 .2/2/2016 http://12tphysicspracticalfilereadings.class 12th.in/ CBSE. V to . mA to ... (vi) Compare the measured values of effective resistances using Meter Bridge with the calculated values.. Least count of voltmeter = . and X2 = ... B......cm RESULT: The value of unknown resistances X1 = .. Range of ammeter = 0 .Physics practical file readings Procedure: (i) Measure the unknown resistances X1and X2 separately using the procedure explained in experiment 2. connect the two in series as shown in figure..blogspot. Least count of ammeter = . and unknown wire in the gaps. Length of the wire of unknown resistance. Take at least three sets of observations for balance point lying between 30 cm and 70 cm. OBSERVATIONS: 1. (ii) After finding the value of X1 and X2. mA 3.in/ 9/45 .class 12th.. (iii) Proceed in the same way as in experiment 2. Range of voltmeter = 0 ...2/2/2016 CBSE. after making the suitable connections as done in experiment 2. Here you can find the value of unknown resistances without interchanging the R... L = .mA 2.V 5. (iv) Calculate the effective resistances using equation (ii)..V 4. http://12tphysicspracticalfilereadings.. 2/2/2016 CBSE. Materials Required: A meter bridge. Theory: A meter bridge is the practical application of Wheatstone bridge arrangement as shown in figure below. screw gauge and connecting wires. galvanometer. Hence the law of combination of resistances in series is verified.Physics practical file readings The value of effective resistance in series: By calculation = . i..class 12th.. a battery jockey. http://12tphysicspracticalfilereadings. unknown resistance wire about 1 meter long. By experiment. one way key.blogspot. a resistance box. EXP4> To find resistance of a given wire using meter bridge and hence determine the specific resistance of its material. The four resistances are connected to each other as shown and if the bridge is inbalanced state...in/ 10/45 .. = . P/Q=R/S We can use this relation to find the unknown resistance of the given material of wire. there is no deflection in the galvanometer (G)..e. The unknown resistance 'X' can be found by Meter bridge which uses the principle of Wheatstone bridge. The unknown resistance 'X' of the given wire is obtained by relation: And specific resistance of the material of a given a wire is obtained by: where d = diameter of the wire and L = length of wire. 2/2/2016 http://12tphysicspracticalfilereadings.blogspot.Physics practical file readings 11/45 .class 12th.in/ CBSE. Physics practical file readings 12/45 .in/ CBSE.class 12th.blogspot.2/2/2016 http://12tphysicspracticalfilereadings. E 2. While interchanging S and R. adjust resistance R so that the null point is somewhere in the middle of the wire AC. introduce some resistance R in the circuit from the resistance box.blogspot. for their continuity. The interchange takes care of unaccounted resistance offered by terminals. Tighten all plugs of the resistance box (RBOX) by pressing each plug.class 12th. From this. Set up the circuit as shown in Fig. 2. ensure that the same length of wire of resistance S is now in the gap F. Note the direction in which pointer of the galvanometer gets deflected in each case. obtain the value of its radius r. 6.in/ 13/45 . Find the average diameter of the wire with a screw gauge. 4.2/2/2016 CBSE. Make sure that jockey remains in contact with the wire for a fraction of a second. especially junctions. Clean the insulation at the ends of connecting wires with a piece of sand paper. Next. 7. 5. If it is not so. null point will be somewhere on the wire AC.1 with unknown resistance wire of known length in gap E.Physics practical file readings Procedure: 1. http://12tphysicspracticalfilereadings. Repeat step 4 for four different values of resistance R. Interchange the position of the resistances S and R and repeat steps 4 to 6 for the same five values of R. between 30 cm and 70 cm. If there is onesided deflection. 3. If the galvanometer shows deflection on both sides of its zero mark for these two points of contact of the jockey. say. check the circuit again. Bring the jockey J in contact with terminal A first and then with terminal C. in/ 14/45 .class 12th... The unknown resistance of the given wire is found to be S + ΔS = .2/2/2016 CBSE..C. L = ..Physics practical file readings OBSERVATIONS: 1. Length of the wire of unknown resistance. . screw gauge and half kg weights.... T = tension applied to the wire. horse shoe magnet.blogspot. m = mass per unit length of the wire http://12tphysicspracticalfilereadings. l = length of the sonometer wire between the two bridges when it is thrown into resonant vibrations. stepdown transformer of 68 volts. Ω 2. ΔS and Δρ are maximum of the five values of error. . The resistivity of the material of the wire is ρ ± Δρ = .. mm Zero error of the screw gauge = .. Measurement of diameter of wire of unknown resistance Least count of the screw gauge (L.mm Zero correction of the screw gauge = .cm 2... Ω m Here S and ρ are mean values..mm RESULT: 1... Materials Required: Sonometer with nonmagnetic wire (brass wire) stretched over it.C mains is given by the following formula: n = 1/2l√ (T/m) Where. EXP5> To find frequency of AC mains with help of a sonometer.. meter scale..) = . Theory: The frequency of A. in/ CBSE.blogspot.Physics practical file readings 15/45 .2/2/2016 http://12tphysicspracticalfilereadings.class 12th. . (vii) Note the density of the material from the table of constants OBSERVATIONS: 1... g/cm = ... Acceleration due to gravity.. m = .. (iv) By increasing the tension on the wire.C mains.. while the secondary to the two ends of the sonometer wire.ms2 http://12tphysicspracticalfilereadings.g = .2/2/2016 CBSE. m 2..cm = . (vi) Measure the diameter of the wire in mutually perpendicular directions at various points.in/ 16/45 . Mass per unit length. (ii) The horse shoe magnet is placed in the middle of the wire such that the magnetic field is applied in a horizontal plane and at right angles to the length of the wire.class 12th. g = . (v) Take readings with decreasing weight.blogspot...Physics practical file readings Procedure: (i) Connect the primary of the step down transformer to A.kg 3... Note the distance l between the two bridges. Mass of the wire = . Length of the wire = .kg/m 4.. repeat the experiment for three or more different tensions. (iii) Hang a mass M ( say ½ kg) from one end of the wire and adjust the distance l between two bridges C and D symmetrically with respect to magnet till the wire appears to be vibrating with the maximum amplitude. It is the combination of P type & Ntype Semiconductor.Hz EXP6> To draw IV characteristics curve of a PN junction in forward bias and reverse bias. Theory: A PN junction is known as Semiconductor diode or Crystal diode. Voltmeter (020V). Which offers Nearly zero resistance to current on forward biasing & nearly infinite Resistance to the flow of current when in reverse biased. Materials Required: Diode Characteristics Kit . Nearly zero resistance is offered to the flow of current. Forward biasing : When Ptype semiconductor is connected to the +ve terminal and Ntype to –ve terminal of voltage source. Connecting Leads..class 12th. Power Supply..Hz (ii) from graph .. Ammeter (020mA). Reverse biasing : When Ptype semiconductor is connected to the –ve terminal and Ntype to +ve terminal.2/2/2016 CBSE.in/ 17/45 .. http://12tphysicspracticalfilereadings. Frequency of ac supply f = n/2 (i) from calculation . Nearly zero current flow in this condition.blogspot.Physics practical file readings RESULT: 1. Physics practical file readings 18/45 .class 12th.blogspot.in/ CBSE.2/2/2016 http://12tphysicspracticalfilereadings. http://12tphysicspracticalfilereadings.. Range of voltmeter = 0 ..blogspot..2/2/2016 CBSE. (3)Vary the value of input dc supply in steps... V to . Range of ammeter = 0 . (2)Switch on the power supply.V RESULT: The graph has been plotted between voltage and current.Physics practical file readings Procedure: (1) Connect the ckt.. Least count of ammeter = .. mA 3. (4)Note down the ammeter & voltmeter readings for each step. as shown in fig..V 4.. Least count of voltmeter = .class 12th..mA 2. mA to ... (5)Plot the graph of Voltage Vs Current OBSERVATIONS: 1.in/ 19/45 . So. the current increases widely even for a small change in voltage.class 12th.The relation between IV is almost linear in this case Vz =Vz0+Iz Rz. we should get a curve very near to xaxis and almost parallel to it for quite sometime. After the Zener potential Vz there will be a sudden change and the graph will become exponential. Vz0 is the voltage at which the straightline approximation of the IV characteristic intersects the horizontal axis. when we plot the graph.2/2/2016 CBSE. where Rz is the dynamic resistance of the zener at the operating point. However.in/ 20/45 .Physics practical file readings EXP7> To draw characteristics of a zener diode and to determine its reverse breakdown voltage. called the breakdown voltage.blogspot. Theory: A Zener Diode is constructed for operation in the reverse breakdown region. After reaching a certain voltage. http://12tphysicspracticalfilereadings. there is no appreciable change in voltage. blogspot.class 12th.in/ 21/45 .2/2/2016 CBSE.Physics practical file readings Procedure: 1.Draw a neat circuit diagram as shown in figure. http://12tphysicspracticalfilereadings. Also ensure that milliammeter is connected in series with Zener diode having protective resistance and voltmeter is connected in parallel with Zener diode. Connect all the components by leads and ensure that the Zener diode is reverse biased. Now adjust the slider of rheostat so that the power supply shows minimum potential. ... 7.in/ 22/45 ..mA Least count of voltmeter =.Physics practical file readings 2.Record all the observations in the table given..class 12th.. Take the value of V..5 V and read the corresponding current in milliammeter to each applied potential............ where it suddenly increases.... 8. 6.. 4.The reverse potential corresponding to this value of reverse.. is called Zener voltage or Breakdown voltage Vz.Continue increasing the potential difference till you get a sudden increase in the reverse current in microammeter. The reverse breakdown voltage of the given Zener Diode is ……………V EXP8> To study characteristics of a common emitter NPN or pnp transistor and to find out the http://12tphysicspracticalfilereadings.2/2/2016 CBSE...... corresponding to I....Plot the graph between V and I as shown.. 3... current is the breakdown or Zener voltage of the Zener diode... Take the observations near the breakdown voltage by varying applied potential difference in the steps of 0. 5.blogspot.Mark on the graph the value of Breakdown Voltage or Zener Voltage Vz as shown. OBSERVATIONS: Least count of milliammeter =.Switch on the power supply and gradually increase the potential difference applied across the Zener diode and note the reading of potential difference from voltmeter also note corresponding value of reverse current in milliammeter...1 V..V RESULT: The characteristic curve of the given Zener is plotted as shown in the graph.Increase the value of applied potential difference in the steps of 0. This value of V.. class 12th.Physics practical file readings value of current and voltage gain. so that carriers can diffuse across it in much less time than the semiconductor’s minority carrier lifetime.2/2/2016 CBSE.In typical operation.blogspot. β=∆Ic/∆Ib http://12tphysicspracticalfilereadings. The electrons in the base are called minority carriers because the base is doped ptype which would make holes the majority carrier in the base.in/ 23/45 .The base region of the transistor must be made thin. Theory: An NPN transistor can be considered as two diodes with a shared anode region. the emitterbase junction is forward biased and the base collector junction is reverse biased. to minimize the percentage of carriers that recombine before reaching the collector base junction. Connect Ammeter between test point 2 and 3 to measure input base current IB (mA).2/2/2016 CBSE. Rotate both the potentiometer P1 and P2 fully in CCW (counter clockwise direction). http://12tphysicspracticalfilereadings. To plot input characteristics proceed as follows : 1. 2.in/ 24/45 .blogspot.class 12th.Physics practical file readings Procedure: Connect 5V and 12V DC power supplies at their indicated position from external source or ST2612 Analog Lab. This curve is the required input characteristic.. b) To determine refractive index of material of prism.. 5. a white sheet of paper.. half meter scale. V to .mA 2. mA to . Repeat the procedure from step 6 for different sets of output voltage VEC. prism. pencil..blogspot. Switch ‘On’ the power supply. drawing pins. Plot a curve between input voltage VEB and input current IB as shown in figure 1 using suitable scale with the help of observation Table l. Range of voltmeter = 0 .Physics practical file readings 3. Vary potentiometer P2 and set a value of output voltage VEC at some constant value (1V.) 7. Requirements: Drawing board.. Vary the potentiometer P1 so as to increase the value of input voltage VEB from zero to 0. 6. Rotate potentiometer P1 fully in CCW direction. Connect one voltmeter between test point 1 and ground to measure input voltage VEB and another voltmeter between test point 6 and ground to measure output voltage VEC. Least count of ammeter = .8V in step and measure the corresponding values of input current IB for different constant value of output voltage VEC in an observation Table 1. http://12tphysicspracticalfilereadings.. 8... Least count of voltmeter = .class 12th. Range of ammeter = 0 .. 3V.V 4. mA 3.in/ 25/45 .V RESULT: Input resistance Rin = ______________ Output resistance Rout = ______________ Current Gain bac = ______________ EXP9> a) To determine angle of minimum deviation for a given prism by plotting graph between angle of incidence and angle of deviation.2/2/2016 CBSE.. OBSERVATIONS: 1. 9. Short or connect a 2mm patch cord between test point 4 and 5 4. 10... 2/2/2016 CBSE. i.Physics practical file readings office pins.in/ 26/45 . parallel to the base so that when δ = δm. Theory: For angle of deviation δ = (i – r) + (e – r′) = i + e – A At the position of the prism for minimum deviation δm. the light ray passes through the prism symmetrically.e.class 12th. graph paper and a protractor.blogspot. The refractive index (n) of the material of the prism is given by where Dm angle of minimum deviation and And A angle of prism. http://12tphysicspracticalfilereadings. i = e which implies r = r′. . P3 O3. Draw straight lines. O3. .blogspot.Physics practical file readings Procedure: 1. O2. corresponding to the incident rays making angles of http://12tphysicspracticalfilereadings. Draw a straight line XY.in/ 27/45 . N3 O3. P1 O1. on these points (Fig. . . . P2 O2. 3.2/2/2016 CBSE. N2 O2. E 13. . 4.2). . . . using a sharp pencil nearly in the middle and parallel to the length of the paper. . Fix a white sheet of paper on a drawing board with the help of cello tape or drawing pins. 2.class 12th. on the straight line XY at suitable distances of about 8 to 10 cm and draw normals N1 O1. Mark points O1.. . .. 6.. ∠P2 O2 N2. 10....2).. 7..Physics practical file readings incidence at 35°. ∠ P3 O3 N3.. on the white paper sheet ( Fig......2/2/2016 CBSE. A = ... 9....in/ 28/45 ... Close one eye (say left) and looking through the prism. to obtain the emergent ray Rl Sl.. with the protractor. Remove the pins Rl and Sl and encircle their pin pricks on the white paper sheet with the help of a sharp pencil. Place the prism with its refracting face AB on the line XY with point O1 in the middle of AB as shown in the figure. 5. ± ... 45°. bring your right eye in line with the images of the pins Pl and Ql. Repeat steps 5 to 9 for different values of angle of incidence (40°.. Produce it backwards to meet the incident ray Pl Ql (produced forward) at T1... . Fix alpins Rl and Sl about 10 cm apart vertically on the white paper sheet with their tips in line with the tips of the images of pins Pl and Ql.. Record observations in tabular form with proper units and significant figures.(degree) RESULT: Angle of minimum deviation.. 11. Draw arrowheads on Pl Ql and R1 S1 to show the direction of the rays. E 13.. In this way pins R1 and S1 will become collinear. 45°. http://12tphysicspracticalfilereadings......... δ 3.. 50°. Remove the pins P1 and Q1 and encircle their pin pricks also.. OBSERVATIONS: Least count of the protractor = . and indicate them in the respective diagrams.(degree) Angle of the prism. Join the points ( or pin pricks) Rl and Sl with the help of a sharp pencil and scale.1) with a protractor and write the values of these angles indicated in the diagram.. δm = . using a protractor. 8. on the incident ray line Pl Ql such that pin Q1 is close to point O1. E 13. Fix two alpins Pl and Q1 with sharp tips vertically about 10 cm apart.. degree Refractive index of the material n =. Write the values of the angles ∠P1 O1 N1.) and measure the corresponding angles of deviation δ2..blogspot.. Draw the boundary of the prism with a sharp pencil. 50°.class 12th..... 40°.. Measure the angle of deviation δ l and the angle BAC (angle A) of the prism (Fig.. with the images of pins P1 and Q1. 60° respectively with the normals. a cell. fractional resistance box.2/2/2016 CBSE. jockey. voltmeter. two one way key. l2 is the balancing length for cell 2 http://12tphysicspracticalfilereadings. Requirements: Potentiometer. l1 is the balancing length for cell 1 E2 emf of primary cell 2 (Daniel cell).Physics practical file readings EXP10> To compare EMF's of 2 given primary cells using potentiometer. high resistance box. galvanometer. ammeter.in/ 29/45 .blogspot.class 12th. connecting wires etc. rheostat of low resistance. Theory: The internal resistance of a cell is given by E1 emf of primary cell 1 (Lechlanche cell). battery. The balancing length AJ = l1 is measured. Using DPDT switch the Leclanche cell is included in the secondary circuit.blogspot.Physics practical file readings Procedure: 1. The circuit is checked for opposite side deflections.2/2/2016 CBSE. 2.in/ 30/45 .class 12th. The point (J) where the galvanometer wire shows full scale deflection is noted. The connections are made as shown in the circuit diagram. The jockey is pressed on the potentiometer wire. 3. 4. http://12tphysicspracticalfilereadings. ......... two one way key... Theory: The internal resistance of a cell is given by http://12tphysicspracticalfilereadings... The above steps are repeated and the balancing length l2 is measured...class 12th..... rheostat of low resistance.in/ 31/45 . 6.V EXP11> To determine the internal resistance of a given primary cell using potentiometer... Using DPDT switch the Daniel cell is included in the secondary circuit...... Requirements: Potentiometer.. By varying the rheostat values l1. jockey.. battery.. a cell.............. fractional resistance box. 8........ RESULT: EMF of 2 given cells are: E1 =. galvanometer.... high resistance box.Physics practical file readings 5.. The ratio of emf of the given two primary calls are calculated using the formula OBSERVATIONS: Balancing length for Lechlanche cell.. 7. l2 are measured and the readings are tabulated...V E2 =.cm.blogspot.2/2/2016 CBSE.. ammeter... Balancing length for Daniel cell.... l2 =.cm.. l1=........ voltmeter...... connecting wires etc. For final reading. After checking the circuit connections. Connect different electrical components as shown in the circuit (Fig.in/ 32/45 . With keys K2 and K3 open and a protective high resistance P from the RBOX 2. 2. close key K1.2/2/2016 CBSE. Procedure: 1. http://12tphysicspracticalfilereadings.class 12th. find the position of the balance point. respectively & R is the shunt resistance in parallel with the given cell. short circuit the resistance P by closing the key K3 and find the balance length lo.1).blogspot. E 5.Physics practical file readings Where length 1 and 2 and are the balancing lengths without shunt & with shunt. OBSERVATIONS: lo=... for concave lens L2 image A′ B′ behaves as virtual object. 6.. close the key K2 and quickly measure the new balance length l . It is http://12tphysicspracticalfilereadings. Keep the readings in the ammeter constant throughout the above observation.in/ 33/45 . mirror and two needles.. Take R = 10 Ω (from RBOX 1).cm(in the beginning of the experiment) lo =. Ω EXP12> To find focal length of a concave lens using a convex lens.. Thus. A real and inverted image A′′ B′′ is formed at point I2 by the diverging lens L2. Ω (ii) by graph . 4. a thin convex lens.. index needle (may be a knitting needle or a pencil sharply pointed at both ends). E 12.2 (b). respectively. a meter scale and a spirit level. RESULT: The internal resistance of the given cell r (i) by calculation . Reduce the value of R in equal steps of 1 Ω and for each value of R obtain the balance length l..blogspot. If a concave diverging lens L2 is inserted between the lens L1 and point I1 as shown in Fig.. for the concave lens L2 the distances O′ I1 and O′ I2 would be the distances u and v.Physics practical file readings 3. a convex mirror.. E 12. Requirements: An optical bench with uprights for holding lens. cm. Theory: A convex lens L1 converges the light rays starting from the object AB to form a real and inverted image A′B′ at position I1 [Fig.2/2/2016 CBSE.cm(in the beginning of the experiment) Mean lo = .. 5..class 12th. Open K2 as soon as this has been done. two needles (pins).. At the end of the experiment.... open key K2 and repeat step 2 to find lo again.2(a)]. blogspot. The focal length of the concave lens L2 can be calculated from the relation Here for the concave lens both distances u and v are positive and since u will be found to be less than v.2/2/2016 CBSE. http://12tphysicspracticalfilereadings.Physics practical file readings important to note that the focal length of convex lens L1 must be smaller than the focal length of the concave lens L2.class 12th.in/ 34/45 . f will always be negative. The second image A′′ B′′ is formed only when the distance between lens L2 and first image A′B′ is less than the focal length of L2. The actual length between the tip of the pin and optical center O′ of the lens L2 would be length of the index needle (as measured by a scale) plus half of the thickness of the lens at its optical center. Place the optical bench on a rigid platform and using the spirit level. 4. if the focal length of the given thin convex lens is not known then rough value of its focal length (fL) should be estimated first to ensure that its focal length is less than that of the concave lens.in/ 35/45 .class 12th. The difference of the two lengths is the index correction. The difference of the two would give the observed length of the index needle. In this condition the planes of lens and both the pins would be perpendicular to the axis of the lens. (If the concave lens is thin at the center. Adjust the index needle (a sharp edged knitting needle would also serve the purpose) horizontally such that its one end touches one of the curved surfaces of the lens and the other end touches the tip of the pin. and the tip of image pin P2 along a horizontal straight line which is parallel to the length of the optical bench. For the determination of the index correction.Physics practical file readings Procedure: 1.blogspot. E 12. Note the positions of the two uprights on the scale provided on the optical bench. 5. You may put a small piece of paper on image pin P2 to differentiate it from the image of object pin P1 [Fig.2/2/2016 CBSE. In case. 2. convex lens L1. and another pin P2 (image pin) on the optical bench. Place the uprights mounted with pin P1 (object pin). bring a mounted pin close to the concave lens L2. make it horizontal with the help of levelling screws provided at the base of the bench. Check the collinearity of the tip of pin P1.2(a)]. optical center O of convex lens L1. its thickness at the center can be ignored). 3. http://12tphysicspracticalfilereadings. Since the image forming at I2 is quite enlarged. 8..e. Actual length between the optical centre O of the lens and tip of the pin. 7.... Adjust the position of the concave lens so that the point I2 is sufficiently away from the point I1. convex lens L1. Thickness of the thin concave lens (given) at its optical centre. Note the readings in the Observation Table. cm 3. t = .. and keeping the image pin P2 at point I1 as a guide to decide which way to shift the concave lens L2..cm. Record these observations in Table E 12. and image pin P2 (i. l = s + t/2 = . 12. move image pin P2 to locate the image (or point I2) more accurately using the method of parallax [Fig.2/2/2016 CBSE. 9. try to see it on moving the concave lens nearer to the point I1 and to locate the image by using a pencil held in hand.. Locate its real and inverted image at point I1 on the other side of the lens by removing the parallax between the image pin P2 and image of the object pin P1 [Fig. Change the position of upright holding the object pin P1 and repeat the steps 6 to 10.3(b)]. s = .blogspot.. Observed length of the index needle. do not change the position of the convex lens L1 and the position of the object pin P1. point I2.3(a)]. l′ = Distance between the pole of the lens and tip of the pin = Position of lens upright position of pin upright on the scale =. Focal length of the convex lens.1. From now on.in/ 36/45 . Read the positions of the uprights holding the object pin P1. Insert the concave lens L2 in between the convex lens L1 and image pin P2. E 12. point I1). Take five sets of observations. cm 5. In case the image formed by the combination of convex and concave lenses is not distinctly visible...class 12th. cm 4. http://12tphysicspracticalfilereadings.Physics practical file readings 6.. 11.. E 12. OBSERVATIONS: 1. Separate the object pin P1 from the convex lens by a distance slightly greater than the focal length fL of the lens. After having seen the clear image at point I2 and ensured that it lies within the range of the optical bench. fL = . Note the position of uprights holding the concave lens and image pin P2. cm 2. it can be blurred.e. i... 10. Length of the index needle as measured by the scale. Now the image of object pin will shift further from the convex lens L1 to a point I2(say). traveling microscope. The refractive index of glass slab or liquid water: http://12tphysicspracticalfilereadings..Physics practical file readings RESULT: The focal length of the given concave lens is (f ± Δf) = . pin.001 cm) attached to the instrument. ± . Requirements: Given liquid or glass slab. Here f is mean value of the focal length.. EXP14> To determine refractive index of a glass slab or transparent liquid using a traveling microscope. lycopodium powder. Theory: A traveling microscope is an ordinary microscope fixed on a stand in such a way that it may be made to travel in vertical as well as horizontal direction without disturbing its adjusted focus.. etc.in/ 37/45 ..blogspot. glass beaker.class 12th.The readings are recorded by means of main scale and vernier scale of high accuracy (0.2/2/2016 CBSE.cm. blogspot.in/ CBSE.2/2/2016 http://12tphysicspracticalfilereadings.class 12th.Physics practical file readings 38/45 . class 12th. 2. Therefore.in/ 39/45 . (Reading 1) 3.blogspot.The given liquid is taken in the beaker. The tip of pin is focussed clearly on the microscope and the corresponding main scale reading (MSR) and vernier scale coincidence (VSC) in the vertical scale are noted in the tabular column.2/2/2016 CBSE. Now the pin is apparently raised through a height.A small pin is fixed horizontally with wax or cello tape at the bottom of the empty beaker.Physics practical file readings Procedure: 1. The microscope is moved up without changing the adjusted http://12tphysicspracticalfilereadings. it will be no longer in focus.The least count of the microscope is determined as in the case of vernier calipers. class 12th.The difference between this Reading 3 and Reading 1 gives the real depth of the liquid....... a convex lens with lens holder.... so that the clear image of lycopodium powder is seen through the microscope.(Reading 2) 4. two outer uprights with lateral movement).. whereas the difference between Reading 3 and Reading 2 gives the apparent depth of the liquid.By substituting the readings in the formula.cm RESULT: The refractive index of glass slab or liquid water =. The microscope is further moved up without changing the adjusted focus.Finally..... 6.. OBSERVATIONS: To find Least count of microscope: Least count: Value of 20 MSD = .. Requirements: An optical bench with three uprights (central upright fixed.Physics practical file readings focus..... the refractive index of the liquid (water) is determined..2/2/2016 CBSE.. (one thin.cm Value of 1 MSD =.. a little lycopodium powder or saw dust which can float on liquid is scattered on the surface of the liquid.... two optical needles. The corresponding main scale reading (MSR) and vernier scale coincidence (VSC) in the vertical scale are noted in the tabular column.in/ 40/45 .. Least Count (LC) = 1/n x value of 1 MSD =... cm No. EXP15> To find focal length of a convex lens by plotting a graph between "u and v" or 1/u and 1/v.... so that the image of the pin is clearly seen through the microscope.... The corresponding main scale reading (MSR) and vernier scale coincidence (VSC) in the vertical scale are noted in the tabular column...blogspot.......... (Reading 3) 5......... of divisions on the vernier scale(n) = .... one thick) a knitting http://12tphysicspracticalfilereadings. through which a ray passes undeviated through the lens. Intercepts of a graph: If a graph cuts xaxis and yaxis.2/2/2016 CBSE. 2. 5.Physics practical file readings needle and a half meter scale.blogspot. TERMS AND DEFINITIONS: 1. Principal axis of a lens is the line joining center of curvature of the two surfaces. Optical center is the point. f= focal length of convex lens u= distance of object needle form optical center of the lens v= distance of image needle from optical center of the lens. Principal focus is the point where rays parallel to the principal axis focus after passing through the lens (convex) or appear to come from after passing through the lens (concave). Theory: The relation between u. v and f for a convex lens is Where.in/ 41/45 . then lengths between origin and points of interception are intercepts http://12tphysicspracticalfilereadings. 3. Focal length is the distance between optical center of lens and focus.class 12th. 4. It can be found by obtaining a sharp image of the Sun or a distant tree on a screen. Place the optical bench on a rigid table or on a platform. http://12tphysicspracticalfilereadings.Obtain approximate value of the focal length of the thin convex lens by focusing the image of a distant object. or a sheet of paper placed on the other side of the lens and measuring the distance between the lens and the image with a scale. say a plane wall.Physics practical file readings Procedure: 1.class 12th. and using the spirit level. 2.in/ 42/45 . f of the convex lens.2/2/2016 CBSE. make it horizontal with the help of leveling screws provided at the base of the bench.blogspot. This distance is a rough estimate of the focal length. . Adjust the index needle (a sharpedged knitting needle would also serve the purpose) horizontally such that its one end touches one of the curved surfaces of the lens and the other end touches the tip of the pin. Displace the object pin P (on left side of the lens) to a distance slightly less than 2f from the optical centre O of the lens (Fig. Locate the position of the real and inverted image on the other side of the lens above the image pin P′. Put a small piece of paper on one of the pins (say on image pin P′) to differentiate it from the object pin P′.class 12th. bring a mounted pin close to the lens. The actual length between the tip of the pin and optical center O would be length of the index needle (as measured by a scale) plus half of the thickness of the lens because optical center of a double convex lens with surfaces of equal curvature is at its geometrical center. In this position. 5. 4. Adjust the pins P and P′ so that the heights of the tips of these pins become equal to the height of the optical center O of the lens from the base of the optical bench. convex lens and image pin on the optical bench and record the readings in an observation table. Find index correction for both the pins.in/ 43/45 .blogspot. Using the method of parallax.3) on left and right hand sides of the lens respectively. Move the object pin P closer to the optical centre O of the lens (say by 2 cm or 3 cm).. 6. Place the vertically mounted sharp pins P and P′ (Fig. Repeat the experiment and record at least six sets of readings for various distances of object pin between f and 2f from the lens.2/2/2016 CBSE.Physics practical file readings 3. 8. Lo =.. cm http://12tphysicspracticalfilereadings. OBSERVATIONS: 1. 9. 7. Clamp the convex lens on an upright and mount it vertically almost near to the middle of the optical bench such that its principal axis is parallel to the optical bench. Length of the index needle as measured by the meter scale.. Note the upright position of the object pin. The difference of the two lengths is the index correction. Note the positions of the two uprights on the scale provided on the optical bench. Approximate focal length of the convex lens = .3). E 10. Let the pin P (placed on left hand side of the lens ) be the object pin and the pin P′ (lying on right hand side) be the image pin. adjust the position of the image pin P′ such that the image of the object pin P coincides with the image pin P′. the lens would lie in a plane perpendicular to the optical bench. E 10. For the determination of the index correction. cm 2. The difference of the two would give the observed length of the index needle. http://12tphysicspracticalfilereadings.cm.. cm =.cm 6. cm – .. t = .blogspot. cm 5. l′o = Distance between the center of convex lens and tip of the object pin = Position of lens upright – position of object pin upright on the scale. 25 marks regarding the performing of the practical is purely passable to the extent of 21 marks.. lo = Lo + t/2 = . you can say perfectly matched and corrected by cross checking from brialliant students in my class. Don't worry about your boards exams. Observed length of the index needle...Physics practical file readings 3...cm Do ask if you have any doubt regarding any topic..in/ 44/45 . I can explain you the things but if you have a doubt regarding readings and my readings shall give the bare idea and then you can overcome some silly mistakes that you might had been making ang these very mistaked might ahve been hindering your perfect readings.. Just prepare for your viva perfectly. All these experiments have been : A. Actual length between the optical center O of the lens and tip of the pin.... = ......cm (here f is mean value of the focal length) (ii) from u – v graph =.. LINK for the whole physics practical lab manual: click here to download lab manual Please do follow my profile for my efforts.cm RESULT: The focal length of the given converging thin convex lens: (i) f ± f = . Index correction for object distance.. Thickness of the thin convex lens (given)... and (iii) from 1/u1/v graph=.. cm 4.2/2/2016 CBSE. eo = lo – l′o = cm; similarly for image pin ei = lil'i = .class 12th.. class 12th.Physics practical file readings AND THERE ARE OTHER POSTS ON MY PROFILE.blogspot. THAT YOU MAY LIKE OR MAKE YOUR SCHOOL DAYS A SMOOTH SAILING.2/2/2016 CBSE. http://12tphysicspracticalfilereadings.in/ 45/45 .