Assertion: In Young's double slit experiment, often both the phenomena interference and diffraction are present
Reason: Diffraction results due to superposition of wavelets from different points of the some wavefront

Answer

To solve the question regarding the assertion and reason in Young's double slit experiment, we will analyze both statements step by step.

### Step 1: Understanding the Assertion
The assertion states that in Young's double slit experiment, both interference and diffraction phenomena are often present.

- **Explanation**: In the double slit experiment, light waves pass through two closely spaced slits and overlap on the other side. This overlap leads to the formation of an interference pattern, characterized by alternating bright and dark fringes. However, since the slits are finite in width, each slit also acts as a source of wavelets that spread out, creating a diffraction pattern. Thus, both interference and diffraction can be observed simultaneously.

### Step 2: Understanding the Reason
The reason provided states that diffraction results from the superposition of wavelets from different points of the same wavefront.

- **Explanation**: According to Huygens' principle, every point on a wavefront can be considered a source of secondary wavelets. When these wavelets overlap, they can interfere with each other, leading to the phenomenon of diffraction. This statement accurately describes how diffraction occurs, as it involves the superposition of wavelets from various points on the wavefront.

### Step 3: Evaluating the Relationship Between Assertion and Reason
Now, we need to determine if the reason correctly explains the assertion.

- **Analysis**: While both the assertion and the reason are correct, the reason does not specifically explain why both interference and diffraction occur in the context of Young's double slit experiment. The assertion is about the presence of both phenomena, while the reason focuses solely on diffraction without addressing how it relates to interference.

### Conclusion
- **Final Answer**: Both the assertion and the reason are correct, but the reason is not the correct explanation of the assertion.