3Check the position of the aperture mask so that the center of the light beam travels directly over the center of the table and parallel to the bench. rotating table of Angular Translator incident ray prism Figure 2.3:Experiment Setup 4Move the arm until the refracted beam is imaged on the viewing screen. 5Now rotate the table and watch the movement of the image (move the arm if necessary). Although the prism is continually rotated in the same direction,note that the image moves in one direction,and then begins moving in the other direction.The point where the image reverses direction coincides with the angle of minimum deviation.That is,at that particular angle of incidence,the light beam is deviated least from its original path. 6Knowing the angle corresponding to minimum deviation(see Figure 2.3),calculate the index of refraction of the prism material from: *NOTE:The edges of the image are colored.Why?This phenomenon is called dispersion. DRotate the table until the refracted beam is parallel to the large surface(slanted surface)of the prism.In this position critical angle no light propagates through the slanted surface;all the light incident is internally reflected.(See Figure 2.4) ray 8Knowing the angle of incidence (0)at which this occurs we can calculate the angle of incidence (0)of the light in the prism as it reaches the slanted surface.The angle 0'is Flgure 2.4 called the critical angle. 9The 900-45-450 prism is designed so that any light normal to the slanted surface is totally internally reflected.Position the prism to observe this phenomenon. Optional Collimate the incandescent beam with the 48mm and 18mm lenses.Then adjust the prism for maximum deviation.By placing spectral filters over the light source,note how the prism refracts the various colors. 2929 ③Check the position of the aperture mask so that the center of the light beam travels directly over the center of the table and parallel to the bench. ④Move the arm until the refracted beam is imaged on the viewing screen. ⑤Now rotate the table and watch the movement of the image (move the arm if necessary). Although the prism is continually rotated in the same direction, note that the image moves in one direction, and then begins moving in the other direction. The point where the image reverses direction coincides with the angle of minimum deviation. That is, at that particular angle of incidence, the light beam is deviated least from its original path. ⑥Knowing the angle corresponding to minimum deviation (see Figure 2.3), calculate the index of refraction of the prism material from: ★NOTE: The edges of the image are colored. Why? This phenomenon is called dispersion. ⑦Rotate the table until the refracted beam is parallel to the large surface (slanted surface) of the prism. In this position no light propagates through the slanted surface; all the light is internally reflected. (See Figure 2.4) ⑧Knowing the angle of incidence (θ) at which this occurs we can calculate the angle of incidence (θ') of the light in the prism as it reaches the slanted surface. The angleθ' is called the critical angle. ⑨The 900 -450 -450 prism is designed so that any light normal to the slanted surface is totally internally reflected. Position the prism to observe this phenomenon. Optional Collimate the incandescent beam with the 48mm and 18mm lenses. Then adjust the prism for maximum deviation. By placing spectral filters over the light source, note how the prism refracts the various colors