A: When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle.
R: Waves diffracted from the edge of the circular obstacle interfere constructively at the centre of the shadow producing a bright spot.

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 assertion and reason question, we will analyze both statements step by step.

### Step 1: Understanding the Assertion
The assertion states that when a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the center of the shadow of the obstacle.

**Explanation**:
- When light from a distant source (which can be considered as plane waves) encounters a small circular obstacle, it creates a shadow region behind the obstacle.
- However, due to the phenomenon of diffraction, light waves bend around the edges of the obstacle.

### Step 2: Understanding the Reason
The reason states that waves diffracted from the edge of the circular obstacle interfere constructively at the center of the shadow, producing a bright spot.

**Explanation**:
- As the light waves bend around the edges of the circular obstacle, they spread out and overlap.
- At the center of the shadow, the waves from the edges of the obstacle meet in phase (i.e., they are aligned), which leads to constructive interference.
- Constructive interference occurs when the crest of one wave aligns with the crest of another wave, resulting in an increase in intensity, hence creating a bright spot.

### Step 3: Conclusion
Both the assertion and the reason are true. The reason correctly explains the assertion because the bright spot at the center of the shadow is indeed due to the constructive interference of the diffracted waves from the edges of the circular obstacle.

### Final Answer:
Both the assertion and the reason are true, and the reason is a correct explanation for the assertion.

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