Assertion: The pattern and position of fringes always remain same even after the introduction of transparent medium in a path of one of this slits.
Reason: The central fringe is bright or dark does not depend uupon the initial phase difference between the two coherence sources.

Options

A. If both assertion and reason are true and reason correct explanation of assertion.
B. If both assertion and reason are true but reason the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question, we need to analyze the assertion and the reason given.

**Assertion:** The pattern and position of fringes always remain the same even after the introduction of a transparent medium in the path of one of the slits.

**Reason:** The central fringe is bright or dark does not depend upon the initial phase difference between the two coherence sources.

### Step-by-Step Solution:

1. **Understanding the Double Slit Experiment:**
- In a double slit experiment, light from a coherent source passes through two slits and creates an interference pattern on a screen. The positions of bright and dark fringes depend on the path difference between the light waves coming from the two slits.

2. **Effect of Introducing a Transparent Medium:**
- When a transparent medium (like a glass slab) is introduced in front of one of the slits, it changes the optical path length for the light passing through that slit. The light traveling through the medium will take longer to reach the screen compared to the light traveling through air.

3. **Central Maxima:**
- The central maxima occurs where the path difference between the two rays is zero. If a medium is introduced, the path difference changes, and thus the position of the central maxima will shift. Therefore, the assertion that the pattern and position of the fringes remain the same is incorrect.

4. **Phase Difference:**
- The reason states that the central fringe being bright or dark does not depend on the initial phase difference. This is also incorrect. The brightness or darkness of the central fringe does depend on the initial phase difference between the two coherent sources. If there is an initial phase difference, it can cause the central fringe to be dark instead of bright.

5. **Conclusion:**
- Since both the assertion and the reason are incorrect, we conclude that the correct answer is: Both assertion and reason are false.

### Final Answer:
Both assertion and reason are false.

---