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? Refractive index of water is 1.33. [Consider the bulb to be a point source]

Explanation

To find the area of the surface of water through which light from a bulb can emerge, we will follow these steps:

### Step 1: Understand the Geometry
The bulb at the bottom of the tank acts as a point source of light. The light will emerge from the water surface in the form of a circular area. The radius of this circle can be determined using the critical angle of refraction.

### Step 2: Determine the Critical Angle
The critical angle (IC) can be calculated using the formula:
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