A : When a diver under water looks obliquely at a fisherman standing on the bank of a lake then fisherman looks taller.
R : When a ray of light travelling in air enters water, it bends towards the normal.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided, and understand the physics behind the phenomenon described.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that when a diver underwater looks obliquely at a fisherman standing on the bank of a lake, the fisherman appears taller. This is a phenomenon related to the refraction of light.

2. **Understanding the Reason (R)**:
- The reason states that when a ray of light traveling in air enters water, it bends towards the normal. This is a fundamental principle of refraction, governed by Snell's law.

3. **Analyzing the Situation**:
- When light travels from a less dense medium (air) to a denser medium (water), it bends towards the normal. The refractive index of water is greater than that of air.

4. **Drawing a Diagram**:
- Visualize the scenario:
- Draw a horizontal line to represent the water surface.
- Above the line, draw the fisherman standing on the bank.
- Below the line, draw the diver underwater.
- Indicate the light rays coming from the fisherman to the diver.

5. **Light Ray Behavior**:
- As the light rays travel from the fisherman (in air) to the diver (in water), they will bend towards the normal at the water's surface. This bending causes the diver to perceive the fisherman’s image at a higher position than where he actually is.

6. **Conclusion**:
- Since the diver sees the light rays as coming from a higher position due to the bending of light, the fisherman appears taller than he actually is. This confirms the assertion.

7. **Final Evaluation**:
- Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the answer is that both A and R are true, and R is the correct explanation of A.