Young's double slit experiment is performed with monochromatic light. A thin film is introduced in front of one of the slits

Options

A. Intensity at the position of central maxima must decrease
B. Intensity at the position of central maxima may increase
C. Central maxima may remain unshifted
D. Intensity at position of first maxima may decreases

Answer

To solve the problem regarding the effect of introducing a thin film in front of one of the slits in Young's double slit experiment, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Young's Double Slit Experiment**:
- In Young's double slit experiment, light passes through two slits and creates an interference pattern on a screen due to the superposition of light waves from the two slits.

2. **Effect of Introducing a Thin Film**:
- When a thin film is placed in front of one of the slits, it introduces an additional optical path difference due to the film's thickness and the refractive index of the material.

3. **Path Difference Calculation**:
- The optical path difference introduced by the thin film can be calculated using the formula:
\[ \Delta = (n - 1) t \]
where \( n \) is the refractive index of the film, and \( t \) is the thickness of the film.

4. **Fringe Shift**:
- The introduction of the thin film causes a shift in the interference pattern. The entire fringe pattern will shift towards the slit with the thin film. This means that the positions of the maxima and minima will change.

5. **Intensity Changes**:
- The intensity at the center maximum may change. Depending on the thickness and refractive index of the film, the intensity at the center maximum can either increase or decrease. However, it is not guaranteed that it will remain the same.

6. **Analyzing the Options**:
- The question provides several options regarding the intensity at the center maximum and the first maximum:
- Intensity at the position of center maxima must decrease.
- Intensity at the position of center maxima may increase.
- Intensity at the position of first maxima may decrease.
- Based on the analysis, we conclude that while the center maximum may shift, its intensity may increase or decrease depending on the specific conditions of the film.

7. **Final Conclusion**:
- The most accurate statement is that the intensity at the position of the first maxima may decrease, and the intensity at the position of center maxima may increase. Therefore, the correct answer is that the intensity at the position of center maxima may increase.