1) the Radii of Curvature for Spherical Surfaces of a Biconvex Lens Are 20Cm and 30Cm.The

Ray Optics 1) The radii of curvature for spherical surfaces of a biconvex lens are 20cm and 30cm.The refractive index of the material of the lens with respect to air is 1.5. If the lens is dipped in a liquid of refractive index 1.65 with respect to air, calculate the effective focal length of lens and state the nature of the lens. [3] 2). What is meant by chromatic aberration of a lens ?Prove that the axial chromatic aberration of a lens is given by fR – fV = ωfY, Where fY is the mean focal length of the lens and ω is the dispersive power of the material of the lens. Start from lens maker’s 3). Draw a neat labeled diagram to show how the image of a distant object is formed by an astronomical refracting telescope in normal adjustment. Obtain an expression for its magnifying power. [4] 4). State the necessary conditions for an achromatic doublet. How are these conditions practically achieved ? [3] 5). The refractive indices for crown glass for red and blue are found to be 1.517 and 1.523;Find the dispersive power of the prism. [3] 6). Find out the focal length of a double concave lens if the radii of curvature are 20cm and 40cm and the refractive index of the glass is 1.5. [3] 7). It is required to form an achromatic combination for an objective of a microscope of focal length 2.1cm.The combination is to use lenses of crown glass and flint glass . Calculate the focal length of the two lenses to be used in the combination and state the type and the material of each lens. Dispersive power of crown glass =0.021, Dispersive power of flint glass =0.031. [4] 8). A prism of μ =1.5 is immersed in water .Compare its deviation with that in air. [3] 9). An object is placed at a distance of 8 cm on the axis of one side of a convex lens of focal length 16 cm. A second convex lens of focal length10 cm is placed coaxially on the other side of it and at a distance of 5 cm from the first lens .Find the position and magnification of the final image formed by lens combination. [3] 10).A real image is formed at a distance of 20 cm from the convex lens .When a concave lens is placed between the convex lens and the screen at a distance of 5cm from the convex lens the image is shifted at a distance of 10 cm .Calculate the focal length of concave lens. [3] 11). Draw a schematic ray diagram of a compound microscope with the final image formed at least distance of distinct vision. [3] 12). .A convex lens of focal length 15cm ,is made of refractive index 1.52. What will be its focal length if it is totally immersed in a liquid of refractive index 1.6? [3] 13). For a ray of monochromatic light passing through a glass prism . draw a graph to show the variation of the angle of deviation (D) with the angle of incidence (i) When does the ray suffer minimum deviation? Derive an expression for the refractive index of the material of the prism in terms of the refracting angle and angle of deviation? [4] 14). Derive Lens Makers formula? [3] 15). Draw a ray diagram to show how the image of a distant object is formed by a refracting astronomical telescope when in normal use? What is the advantage of using a reflecting telescope over refracting telescope? [4] 16). A compound microscope consists of an objective lens of focal length 2 cm and an eye piece of 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at infinity? What is the magnifying power of the microscope? [4] 17). What is the cause of spherical aberration in lenses? How is it rectified? [3] 18). The refractive indices of a prism for violet, yellow and red colours are 1.632, 1.620 and 1.613 respectively? Calculate the dispersive power of the material of the prism? [3] 19). Derive an equation relating u, v and R in the case of refraction at a convex spherical surface separating medium of refractive index n1 from a medium of refractive index n2 .State the assumption used? [3] 20). Figure shows a solid sphere of radius 5cm and that has a small air bubble B trapped at a distance 2cm from the centre C. The refractive index of the material of glass is 1.5.Find the apparent position of the bubble where it will appear , when seen through the surface of the sphere from an outside point E [3]

21). What is meant by pure spectrum? What are the conditions for pure spectrum? [3] 22). What is the angle of flint glass prism of refractive index 1.695 which must be combined with a 50 crown glass prism of refractive index 1.523 in order that the angle of deviation is zero? [3] 23). Define the angular magnification of an optical instrument. [2] 24). Define dispersive power (for light) of a medium. [2] 25). What are the two possible values of the magnifying powers of a simple microscope made of convex lens of focal length f=5 cm. [2] 26). The dispersive power of an achromatic doublet is 2/3 and the combined focal length of the combination is 30 cm. Find the focal length of each lens stating its nature. [3] 27). Derive the formula of angular magnification of a compound microscope, when the final image is formed at least distance of distinct vision. Draw the required ray diagram. [4] 28) At what angle should a light ray be incident on the face of a 600 prism so that the ray just suffers total internal reflection at the other face? The refractive index of the prism is 1.524 [2] 29) An object is placed at a distance of 8 cm on the axis of one side of a convex lens of focal length 16cm. A second convex lens of focal length10 cm is placed coaxially on the other side of it and at a distance of 5 cm from the first lens .Find the position and magnification of the final image formed by lens combination. [3]