The way the fringe pattern changes when the sceen is moved away from the slits is

Options

A. width of frings increases
B. width of fringe decreases
C. no changesobserved
D. change will vary

Answer

To solve the problem, we need to analyze how the fringe pattern changes when the screen is moved away from the slits in a double-slit interference experiment.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- In a double-slit experiment, we have two slits (S1 and S2) that produce an interference pattern on a screen placed at a distance (D) from the slits. The distance between the two slits is denoted as (d).

2. **Fringe Width Definition**:
- The fringe width (β) is defined as the distance between two consecutive bright or dark fringes. It can be calculated using the formula:
\[ \beta = \frac{\lambda D}{d} \]
where:
- \( \lambda \) = wavelength of the light used,
- \( D \) = distance from the slits to the screen,
- \( d \) = distance between the two slits.

3. **Effect of Moving the Screen**:
- When the screen is moved away from the slits, the distance \( D \) increases.

4. **Analyzing the Formula**:
- Since \( \beta \) is directly proportional to \( D \) (as seen in the formula), if \( D \) increases, \( \beta \) will also increase. This means the distance between the fringes will become larger.

5. **Conclusion**:
- Therefore, when the screen is moved away from the slits, the fringe width increases, resulting in a wider spacing between the bright and dark fringes on the screen.

### Final Answer:
- The way the fringe pattern changes when the screen is moved away from the slits is that the fringe width increases.