Posted Date: 24 Jan 2009      Posted By:: Smt sangeeta mehta    Member Level: Silver  Points: 5 (Rs. 1)

# 2008 CBSE practice questions:Class:XII:Physics:Optics-II Question paper

 Course: Plus II University/board: CBSE

practice questions:Optics-II
M.M.:25 Class: XII, Sub.; Physics T.A.:1 H
1. The lens shown in the fig. Is made of two different transparent materials. A point object is placed on its axis. How many images of the object will de formed? Explain. 1.
2. If the wave length of incident light on convex lens is increased, how will the focal length changes? 1.
3. A concave mirror and a convex lens are held in water. What change, if any, do you expect in their respective focal lengths as compared to their values in air? 1.
4. By drawing the ray diagrams, show how a right angled isosceles prism can be used to deviate a ray of light through (i) 900 and (ii) 1800 . 2.
OR
The image obtained with a convex lens is erect and its length is 3 times the length of the object. If the focal length of the lens is 15 cm, calculate the distance of image formed. (u= -10 cm, v= -30 cm)
5. Define the wave front and name the types. State the Huygen’s principle of secondary wavelets. 2.
6. Explain total internal reflection. State the conditions. 2.
OR
Explain the principle used in optical fiber. Give two main uses of optical fiber.
7. Write the differences between interference and diffraction. 2.
8. Explain the dispersion of light through prism draw the graph between angle of deviation and angle of incident. State the condition for minimum deviation. Refractive indices for blue, red and yellow colors are µb, µr and µy. Write them in decreasing order of values. 3.
9. Draw the labeled diagram for compound microscope and derive the relation for magnifying power. 3.
10. What are coherent source of light? Why no interference pattern is observed when two coherent sources are (i) infinitely closed to each other? (ii) Far apart from each other? 3.
OR
Explain the polarization of light. Describe the method to obtain the polarized light by reflection. What is the polarizing angle of a medium of refractive index 1.732?
11. Discuss the refraction through convex surface. Hence derive the lens maker’s formula. The radii of curvature of a double concave lens are 30 cm and 60 cm and its refractive index is 1.5. Calculate the focal length of the lens. 5.

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