CBSE Class 12 Physics Optics Assignment

CBSE Class 12 Physics Optics Assignment. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Comprehension-1
When light ray passes from one medium to the other its speed changes, which can deviate the ray from its original path. The relationship between angle of incidence and angle of refraction on the interface of two media is sin i/ sin r =v₁/v₂ = μ₁/μ₂ , where μ₁ and μ₂ refractive index of the two media and v₁, v₂ are velocity of light in the two media. Since most of the transparent mediums are dispersive in nature i.e., velocity of wave depends on frequency of wave (light), white light gets dispersed.

1. Image of a white object (point like) made by a lens is not a point. Its reason is
(a) different colours have different focal length
(b) surface of lens is not perfectly spherical
(c) motion of air molecule changes refrective index of air which changes the path of rays rapidly.
(d) all of these

2. White light passes through prism and get deviated from its path due to
(a) different colours of light has equal velocity in the prism.
(b) velocity of light changes when light enters in the prism and when it comes out of prism.
(c) due to dispersive nature of the material of prism .
(d) all of these

Comprehension-2

It is found that when light passes through any medium its wavelength depends on the medium according to the given relation, λ =  λa /μ2, where λa is wavelength of light in air, μ is constant and characteristic of medium.

3. What is maximum value of μ of medium so that light travelling in air and medium of the same length are in same phase again if they were in same phase when light entered in the medium. (length of air column and medium is same)
(a) 1.5 (b) 1.75 (c) 1.4 (d) 1.6

4. If length of medium is 3 cm and μ = √2 . The phase of the light , when it comes out of medium (λa = 2 cm)
(a) lags behind by 2π with entering wave (b) leads by 4π with entering wave
(c) lags by 6π with entering wave (d) leads by 6π with entering wave

Comprehension-3

When we solve the problems regarding position of image made by spherical mirrors, we use the formula 1/u, 1/v, 1/R,u , u, v and R are the distances of object, image and centre of curvature of mirror. According to sign convention direction of incident ray is taken as positive direction and all the distances must be measured from pole. For image length we use the concept of lateral magnification. Which is m=I/O= - v/u Where I and O are length of image and length of object respectively.

5. A car is fitted with a convex mirror of focal length 20 cm. A second car 2 m broad and 1.6 m high is 6 m away from the first car. The position of the second car as seen in the mirror of the first car is
(a) 19.35 cm (b) 17.45 cm (c) 21.48 cm (d) 15.49 cm

6. In the above question, the breadth and height of the second car seen in the mirror of the first car, are respectively
(a) 5.79 cm, 6.9 cm (b) 6.45 cm, 5.16 cm (c) 2.7 cm, 4.8 cm (d) 0.1 m, 0.3 m

7. A candle is placed in front of a concave mirror. The image of candle is formed on a wall at a distance of 2 m from the candle. The size of the image is 6 times that of the candle. The distance of the candle from the mirror is
(a) 1.6 m (b) 2.4 m (c) 2 m (d) 0.4 m

8. In above question, the focal length of the mirror used is
(a) 0.343 m (b) 0.47 m (c) 3.43 cm (d) 4.8 cm

Each of the questions given below consists of two statements, an assertion (A) and reason (R).
Select the number corresponding to the appropriate alternative as follows
(a) If both A and R are true and R is the correct explanation of A
(b) If both A and R are true but R is not the correct explanation of A
(c) If A is true but R is false
(d) If A is false but R is true

9. A: Sources having different frequencies can not be coherrent.
R: Sources having same frequency and variable phase are coherent sources.

10. A: When one of the slits in double slit experiment is covered with opaque material, the interference pattern disappears.
R: Two coherent sources are required to produce interference pattern.

11. A: Fringes produced by the light of shorter wavelength will be narrower as compared to those produced by light of longer wavelength.
R: Fringe width, β ∝ λ.

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