A : In double slit experiment, the pattern on the screen is actually a superposition of sngle-slit diffraction from each slit and the double -slit interference pattern.
R : The diffraction pattern has a central bright maximum which is twice as wide as the other maxima.

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 problem, we need to analyze the assertion (A) and the reason (R) provided in the context of the double slit experiment.

### Step 1: Understanding the Assertion (A)
The assertion states that in a double slit experiment, the pattern observed on the screen is a superposition of single-slit diffraction from each slit and the double-slit interference pattern.

- **Explanation**: When monochromatic light passes through two closely spaced slits, each slit acts as a source of wavefronts. The light waves from each slit undergo diffraction, which causes them to spread out. The overlapping of these diffracted waves from both slits leads to an interference pattern on the screen. Thus, the overall pattern is indeed a combination of single-slit diffraction and double-slit interference.

### Step 2: Understanding the Reason (R)
The reason states that the diffraction pattern has a central bright maximum that is twice as wide as the other maxima.

- **Explanation**: In single-slit diffraction, the central maximum is indeed wider than the other maxima. This occurs because the intensity of the light decreases as you move away from the center, leading to a wider central maximum. The central maximum is typically twice as wide as the other maxima due to the nature of the diffraction pattern produced by a single slit.

### Step 3: Evaluating the Truth of A and R
- **Truth of A**: The assertion is true because the pattern on the screen is indeed a superposition of single-slit diffraction and double-slit interference.
- **Truth of R**: The reason is also true as the central maximum in the diffraction pattern is wider than the other maxima.

### Step 4: Analyzing the Explanation
While both the assertion and reason are true, the reason does not correctly explain the assertion. The assertion is about the overall pattern being a combination of diffraction and interference, while the reason specifically addresses the width of the central maximum, which is a characteristic of single-slit diffraction alone.

### Conclusion
Both the assertion (A) and reason (R) are true, but R is not the correct explanation of A. Therefore, the correct answer is that both A and R are true, but R is not the correct explanation of A.

### Final Answer
Both A and R are true, but R is not the correct explanation of A.

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