Total Internal Reflection

Practice Questions:

Question 1: moderate

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 then what is the value of critical angle ?

1. \[sin^{-}(tani)\]

2. \[cos^{-}(tani)\]

3. \[sin^{-}(coti)\]

4. None of these

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Question 2: moderate

The speed of light in media M1 and M2 is \[1.5\times 10^{8} m/s and 2.0\times 10^{8}\] respectively. A ray of light enters from medium M1 to M2 at an incidence angle i. If the ray suffers total internal reflection, the value of i is :

1. Equal to or less than sin–¹(3/5)

2. Equal to or greater than sin–¹(3/4)

3. Less than sin–¹(2/3)

4. Equal to sin–¹(2/3)

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Question 3: moderate

A transparent solid cylindrical rod has a refractive index of 2/√3. It is surrounded by air. A light ray is incident at the mid-point of one end of the rod as shown in the figure.

The incident angle θ for which the light ray grazes along the wall of the rod is

1. \[sin^{-1}(1/2)\]

2. \[sin^{-1}(\sqrt{3}/2)\]

3. \[sin^{-1}({2}/\sqrt{3})\]

4. \[sin^{-1}({1}/\sqrt{3})\]

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Question 4: moderate

A point source of light is kept at a depth of h in water of refractive index 4/3. The radius of the circle at the surface of water through which light emits is

1. \[\frac{3}{\sqrt{7}}h\]

2. \[\frac{\sqrt{7}}{3}h\]

3. \[\frac{\sqrt{3}}{7}h\]

4. \[\frac{7}{\sqrt{3}}h\]

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Question 5: moderate

A small coin is resting on the bottom of a beaker filled with liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface. How fast is the light travelling in the liquid ?

1. \[2.4\times 10^{8}m/s\]

2. \[3.0\times 10^{8}m/s\]

3. \[1.2\times 10^{8}m/s\]

4. \[1.8\times 10^{8}m/s\]

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