Page 1 CBSE TEST PAPER-04 CLASS - XII PHYSICS (Ray Optics) 1. The refractive index of a material of a convex lens is n 1 it is immersed in a medium of refractive index n 2. A parallel beam of light is incident on the lens. Trace the path of the emergent rays when n 2 > n 1. [1] 2. In a telescope the focal length of the objective and the eye piece are 60cm and 5cm respectively. What is? (1) Its magnification power (2) Tube length [1] 3. Although the surfaces of a goggle lens are curved it does not have any power. Why? [2] 4. A ray of light in incident normally on one face of the prism of apex angle 30 o and refractive index 2 . Find the angle of deviation for the ray of light? [2] 5. A reflecting type telescope has a concave reflector of radius of curvature 120cm. calculate the focal length of eye piece to secure a magnification of 20? [3] 6. Show that a convex lens produces an N time magnified image, when the object distances from eh lens have magnitude f f N ? ? ± ? ? ? ? . Here f is the magnitude of the focal length of the lens. Hence find two values of object distance. For which a convex lens of power 2.5 D will produce an image that is four times as large as the object? [3] 7. Define total infernal reflection of light? Hence write two advantages of total reflecting prisms over a plane mirror? [3] 8. (a) A person looking at a mesh of crossed wires is able to see the vertical lines more distinctly than the horizontal wires. What is the effect due to? How is such a defect of vision corrected? [2] (b) A man with normal near point (25cm) reads a book with small print using a magnifying glass: a thin convex lens of focal length 5cm. (i) What is the closest and the farthest distance at which he can read the book when viewing through the magnifying glass ? (ii) What is the maximum and minimum angular magnificent (magnifying power) possible using the above simple microscope? [3]Read More

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