A person standing waist-deep in a swimming pool appears to have short legs because of light?

Analysis

The question asks for the physical phenomenon responsible for the visual distortion of an object (in this case, a person's legs) when viewed through a medium different from air (water).

Concept Explanation

This phenomenon is explained by Refraction. Refraction is the bending of light as it travels from one medium to another of different optical density (e.g., from water to air).

1. Optical Density: Water is optically denser than air.
2. Bending of Light: When light rays reflected from the person's legs travel from the water into the air, they move from a denser medium to a less dense medium. According to Snell's Law, the light rays bend away from the normal.
3. Apparent Position: Our eyes trace these light rays back in a straight line. Because the rays have bent, the brain perceives the legs to be at a shallower depth than they actually are. This makes the legs appear shorter or "raised" compared to the rest of the body above the water.

Step-by-Step Solution

• Step 1: Identify the media involved: Water (denser) and Air (less dense).
• Step 2: Recognize that light travels at different speeds in these two media.
• Step 3: Apply the principle of refraction: As light leaves the water, it changes direction (bends).
• Step 4: Conclude that the change in the path of light causes the image to appear displaced, leading to the illusion of shortened legs.

• Diffraction (Option A) involves the spreading of waves around obstacles.
• Reflection (Option C) involves light bouncing off a surface.
• Interference (Option D) involves the superposition of two or more waves.

None of these explain the change in the apparent position of an object submerged in a liquid.

Correct Answer

The correct option is B.

Exam Tip

Whenever you see a question about objects appearing "bent," "shortened," or "raised" in water (like a stick in a pool or a coin at the bottom of a cup), the answer is almost always Refraction. Think of it as the "bending" of light!