A : There is no specific important physical difference between interference and diffraction.
R : When there are only few sources (say two), the result is usually called interference, but if there is a large number of sources, the result is diffraction.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true and R is not the correct explanation of A
C. A is true and R is false
D. Both A and R are false

Answer

To solve the question, we need to analyze the two statements provided: the assertion (A) and the reason (R).

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states: "There is no specific important physical difference between interference and diffraction."
- To evaluate this, we need to recognize that interference and diffraction are both wave phenomena related to light, but they exhibit different characteristics and patterns.

2. **Analyzing Interference**:
- Interference occurs when two or more coherent light sources overlap, resulting in a pattern of bright and dark fringes.
- The bright fringes have the same intensity, and the pattern is stable and periodic.

3. **Analyzing Diffraction**:
- Diffraction occurs when light waves encounter an obstacle or aperture, causing them to spread out and create a pattern.
- The intensity of the diffraction pattern decreases from the center, meaning the central maximum is the brightest, and the intensity diminishes for subsequent maxima.

4. **Conclusion on Assertion (A)**:
- Since interference and diffraction produce different patterns and have distinct characteristics, the assertion is **false**.

5. **Understanding the Reason (R)**:
- The reason states: "When there are only a few sources (say two), the result is usually called interference, but if there is a large number of sources, the result is diffraction."
- This statement accurately describes the relationship between the number of sources and the resulting phenomenon.

6. **Conclusion on Reason (R)**:
- The reason is **true** as it correctly explains the distinction between interference (with few sources) and diffraction (with many sources).

7. **Final Evaluation**:
- Since assertion A is false and reason R is true, we conclude that the correct answer is:
- Assertion A is **false**.
- Reason R is **true**.

### Final Answer:
- Assertion A: False
- Reason R: True