HARD
12th West Bengal Board
IMPORTANT
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A coin is placed at the bottom of an empty hemispherical basin. When looked over the edge of the basin, the coin is just invisible, but becomes just visible when the basin is filled up by a liquid. If r be the radius of the coin, show that r=a(u2-1) /(u2+1) where u=r . i. of the liquid and a= radius of the hemisphere.

Important Questions on Refraction of Light

MEDIUM
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 10
A given monochromatic light ray initially in air strikes a 90° prism and is refracted to such an extent that it just grazes the prism surface after emerging into air. If the angle of incidence is 60°, find the refractive index of the prism. 
MEDIUM
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 11
A nail is fixed perpendicularly to a circular wooden disc at its centre. The disc is floated in water with the nail downwards. What must be the ratio of the longest possible length of nail to the radius of the disc, so that the nail is completely invisible from air? Critical angle for water =48°30'
HARD
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 12

A ray of light from a denser medium strikes a rarer medium at an angle of incidence i . The reflected and the refracted rays make an angle of 90° with each other. The angles of reflection and refraction are i and r' Show that the critical angle θc is given by θc=sin-1(tanr)

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HARD
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 13
A small bulb is placed at the bottom of a tank containing water to a depth of 80 cm. What is the area of the surface of water through which light from the bulb can emerge out? The Refractive index of water is 1.33. Consider the bulb to be a point source of light.  
HARD
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 14
A small luminous source at the bottom of a pool of water(μ=4/3)1 metre deep, emits rays upward in all directions. A circular area of light is formed at the surface of water. Determine the radius of the circle. 
HARD
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 15
A ray of light falls on the plane horizontal face of a square glass slab at an angle of 45°. It is refracted into the block and is incident on one vertical face. What must be the refractive index of glass if total reflection occurs at the
HARD
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 16
Light enters a prism of refracting angle A at grazing incidence to emerge at an angle θ with normal. Show that the refractive index of the material of prism is :
μ=1+cosA+sinθsinA212   
HARD
12th West Bengal Board
IMPORTANT
A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 17
The refracting angle of a prism is 30°. One of its refracting faces has a coating. A ray of light incident on the other face at an angle 45° falls on the coated surface. On reflection, the ray retraces its path. Find the refractive index of the material of the prism.