CBSE Class 12 Physics 2022 Term 2 Outside Delhi Set 1 Solved Paper

Question : 8

Total: 12

(a) Write two necessary conditions for total internal reflection.
(b) Two prisms ABC and DBC are arranged as shown in figure.

The critical angles for the two prisms with respect to air are 41.1circ and 45circ respectively. Trace the path of the ray through the combination. 3
OR
(a) An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is (i) negative and (ii) positive.
(b) A point object is placed at O in front of a glass sphere as shown in figure.

Show the formation f image by the sphere.

Solution:

(a)Necessary conditions for total internal reflection:
- Light should travel from denser to rarer medium.
- Angle of incidence should be greater than the critical angle for the pair of media and the colour of light used.
(b) The ray incident normally at M enters undeviated.
At E, angle of incidence is 45circ. It is greater than the critical angle. So, it is totally internally reflected.

At H, the ray is incident normally. So it enters prism BDC undeviated.
At F, the angle of incidence is 60°. It is greater than the critical angle. So, it is internally reflected.
At G, the ray is incident normally. So, it comes out from the prism undeviated.
OR
(a) (i) Magnification is negative for real image formed by convex lens.
(ii) Magnification is positive for virtual image formed by convex lens.
(b)

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