CBSE Class 12 Physics Optics Advanced Problems

CBSE Class 12 Physics Optics Advanced Problems. 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.

1. A 16 cm long pencil is placed at 45º angle with its centre 15.0 cm above the optic axis and 45.0 cm from a convex lens of focal length 20 cm as shown in figure. Assume that the diameter of the lens is large enough for the paraxial approximation to be valid :

(a) where is the image of the pencil formed. (Give the location of the images of the points A, B and C w.r.t. coordinate system shown in the figure)
(b) what is the length of the image (the distance between the images of points A and B).

2. Two converging lenses of the same focal length f are separated by distance 2f. The axis of the second lens is inclined at angle θ = 60º with respect to the axis of the first lens. A parallel paraxial beam of light is incident from left side of the lens. Find the coordinates of the final image with respect to optical centre of firs lens as origin.

3. A double convex lens forms a real image of an object on a screen which is fixed. Now the lens is given a constat velocity v0 along its axis and away from the screen. For the purpose of forming the image always on the screen, the object is also required to be given appropriate velocity. Find the velocity of the object at the instant its size is n times the size of the image. (n < 1).

4. A ray of light is incident on the surface of a sphere of refractive index √7 /2 . Other half of the sphere is silvered. After refraction it is reflected and then refracted out of the sphere again such that the total deviation is minimum. Find :

(a) the angle of incidence of the ray i
(b) total deviation of the ray,(sin 41º = √3/7) .

5. The refracting angle of prism is 60º. A ray of light passing through the prism undergoes a deviation of 30º. If the prism is rotated keeping the incident ray fixed through an angle 30º, the same deviation is again obtained. Calculate the refractive index of the prism.

6. A thin biconvex lens of refractive index 3/2 is placed on a horizontal plane mirror as shown in the figure. The space between the lens and the mirror is then filled with water of refractive index 4/3. It is found that when a point object is placed 15 cm above the lens on its principal axis, the object coincides with its own image. On repeating with another liquid, the object and the image again coincide at a distance 25 cm from the lens. Calculate the refractive index of the liquid.

7. A convex lens of focal length 15 cm and a concave mirror of focal length 30 cm are kept with their optic axis PQ and RS parallel but separated in vertical direction by 0.6 cm as shown. The distance between the lens and mirror is 30 cm. An upright object AB of height 1.2 cm is placed on the optic axis PQ of the lens at a distance of 20 cm from the lens. If A′B′ is the image after refraction from the lens and the reflection from the mirror, find the distance of A′B′ from the pole of the mirror and obtain its magnification. Also locate positions of A′ and B′ with respect to the optic axis RS

8. The X-Y plane is the boundary between two transparent media. Medium-1 with z ≥ 0 has a refractive index √2 and medium-2 with z ≤ 0 has a refractive index √3 . A ray of light in medium-1 given by vector A = 6 √3 iˆ + 8 √3 ˆj –10 kˆ is incident on the plane of separation. Find the unit vector in the direction

of the refracted ray in medium-2

(a) Calculate the wavelength λ0 for which rays incident at any angle on the interface BC pass through without bending at that interface.
(b) For light of wavelength λ0, find the angle of incidence i on the face AC such that the deviation produced by the combination of prisms is minimum.

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