INTRODUCTIONIn optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use "prism" Typical materials include glass. Prisms can be made from any material that is transparent to the wavelengths for which they are designed.usually refers to this type. A prism can be used to break light up into its constituent spectral colors (the colors of the rainbow). . plastic and fluorite. Some types of optical prism are not in fact in the shape of geometric prisms. Prisms can also be used to reflect light. or to split light into components with different polarizations. Newton's experiments demonstrated that all the colors already existed in the . and that the prism itself produced the color.PRISM AND NATURE OF LIGHT Before Isaac Newton. it was believed that white light was colorless. Newton arrived at his conclusion by passing the red color from one prism through a second prism and found the color unchanged. the prism did not create colors. He also used a lens and a second .light in a heterogeneous fashion. It was only later that Young and Fresnel combined Newton's particle theory with Huygens' wave theory to show that color is the visible manifestation of light's wavelength. but merely separated colors that are already there. and that "corpuscles" (particles) of light were fanned out because particles with different colors traveled with different speeds through the prism. he concluded that the colors must already be present in the incoming light — thus. From this. A quantitative were introduced in the 1980s. [1] He also introduced the use of more than one prism to control dispersion. leading to John Locke's primary vs secondary quality distinction. and is quite readable. . This experiment has become a classic example of the methodology introduced during the scientific revolution. Newton discussed prism dispersion in great detail in his book Opticks.[2] Newton's description of his experiments on prism dispersion was qualitative. The results of this experiment dramatically transformed the field of metaphysics.prism to recompose the spectrum back into white light. THEORY . The degree of bending of the light's path depends on the angle that the incident beam of light makes with . from air into the glass of the prism).HOW DOES A PRISM WORK? Light changes speed as it moves from one medium to another (for example. This speed change causes the light to be refracted and to enter the new medium at a different angle (Huygens principle). Furthermore. creating an effect similar to a rainbow. and on the ratio between the refractive indices of the two media (Snell's law). The refractive index of many materials (such as glass) varies with the wavelength or color of the light used. making them useful for broad-spectrum spectroscopy.the surface. prisms do not suffer from complications . a phenomenon known as dispersion. This can be used to separate a beam of white light into its constituent spectrum of colors. This causes light of different colors to be refracted differently and to leave the prism at different angles. Prisms will generally disperse light over a much larger frequency bandwidth than diffraction gratings. Prisms are sometimes used for the internal reflection at the surfaces rather than for dispersion. It is represented by the symbol Dm. Angle of Minimum Deviation The minimum value of angle of deviation. total internal reflection occurs and all of the light is reflected. This makes a prism a useful substitute for a mirror in some situations. which all gratings have. One value equals ’i’ and . For same angle of deviation (D) there are two values of angle of incidence. If light inside the prism hits one of the surfaces at a sufficiently steep angle. is called angle of minimum deviation.arising from overlapping spectral orders. When angle of deviation is minimum(Dm). ‘i’ and ‘e’ becomes equal. Board pins Drawing board . spirt and coconut oil.other value equals ‘e’ As angle ‘i’ is increased from a small value. ‘e’ decreases from large value and angle of deviation decreases. AIM To find out the refractive indices of different liquids using a hollow prism APPARATUS REQUIRED Hollow glass prism Various liquids like water. then. Keep the prism and mark the outline of it as ABC. .PROCEDURE Fix a white sheet of paper on the drawing board with help of drawing pins. Drop a normal PQ on the side AB. on the marked outline ABC. Mark the diagram as shown in the figure. Now take the pins and place them on the side AC so that all the 4 pins appear to be in same line. . Remove the prism and draw the line joining the points so obtained. Draw the angle of incidence in accordance with the normal PQ and place 2 pins so that they appear to be in the straight line. Place the prism filled with given sample of liquid . Repeat this with different liquids and different angle of incidence. Observation Benzaldehyde S.5 4 60 39 d º (angle of deviation) 45 42 40 42 .n a º(angle i º (angle o of prism) of incidence) 1 60 30 2 60 35 3 60 37. 5 60 40 45 U=sin((60+40)/2)/sin(30) = 1.306 Dil.504 Water S.n a º(angle i º (angle o of prism) of incidence) 1 60 30 2 60 35 3 60 40 4 60 45 5 60 50 6 60 55 d º (angle of deviation) 25 22 20 22 25 28 U=sin((60+22)/2)/sin(30) = 1. Sulphuric Acid . S.351 Conclusion Refractive indices at room temperature: Benzaldehyde oActual: 1.n a º(angle i º (angle o of prism) of incidence) 1 60 20 2 60 30 3 60 35 4 60 40 5 60 45 d º (angle of deviation) 33 30 25 29 30 U=sin((60+25)/2)/sin(30) = 1.546 . oExperimental: 1. . Sulphuric acid oActual: 1.355 oExperimental: 1.504 o Water oActual: 1.306 o Dil .33 oExperimental: 1.351 Precautions Angle of incidence should lie b/w 35-60 degree. Pins should be vertically fixed and should lie in same line. Record your observation. Arrow head should be marked to represent emergent and incident ray. . Same angle of prism should be used for all observation. Distance b/w two points should not be less than 10mm.
Report "204529344 Hollow Prism Physics Investigatory Project Class 12 CBSE"