Class XII Physics Ray Optics 4

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Question 1

A ray of light from a denser medium strikes a rarer medium at an angle of incidence i. If the reflected and refracted rays are mutually perpendicular to each other, what is the value of critical angle?

• Asin^–1 (cot i)
• Bsin^–1 (tan i)
• Ccos^–1 (cot i)
• Dcos^–1 (tan i)

Question 2

A layer of benzene (μ₁ = 1.5) 6 cm deep floats on water (μ₂= 1.33) 4 cm deep. When viewed vertically through air the apparent distance of the bottom of the vessel below the surface of the benzene will be -

• A14 cm
• B7 cm
• C21 cm
• D3.5 cm

Question 3

A cylinder is filled with a liquid of refractive index μ. The radius of the cylinder is decreasing at a constant rate K. The volume of the liquid inside the container remains constant at V. The observer and the object O are in a state of rest and at a distance L from each other. The apparent velocity of the object as seen by the observer, (when radius of cylinder is r) –

• A
• B
• C
• D

Question 4

At what distance from a concave mirror of focal length 10 cm must an object be placed in order that an image double its size may be obtained -

• A5 cm only
• B15 cm only
• Ceither 5 cm or 15 cm
• Dat 10 cm

Question 5

A point object is placed midway between two plane mirrors distance 'a' apart. The plane mirrors form an infinite number of images due to multiple reflections. The distance between n^th order images formed in the two mirrors is -

• Ana
• B2 na
• C
• Dn² a

Question 6

A luminous point object is moving along the principal axis of a concave mirror of focal length 12 cm towards it. When its distance from the mirror is 20 cm its velocity is 4 cm/s. The velocity of the image in cm/s at that instant is:

• A6, towards the mirror
• B6, away from the mirror
• C9, away from the mirror
• D9, towards the mirror

Question 7

A point object at 15 cm from a concave mirror of radius of curvature 20 cm is made to oscillate along the principal axis with amplitude 2mm. The amplitude of its image will be:

• A2 mm
• B4 mm
• C8 mm
• Dnone of these

Question 8

A parallel beam of light travelling in water (refractive index = 4/3) is refracted by a spherical air bubble of radius 2cm situated in water. Assuming the light rays to be paraxial, the position of the image due to refraction at the first surface is -

• A6cm from the first surface
• B12 cm from the first surface
• C3cm from the first surface
• D10 cm from the first surface

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