If the source of light used in a Young's Double Slit experiment is changed from red to blue, then

Options

A. the fringes will become brighter
B. consecutive fringes will come closer
C. the number of maxima formed on the screen increases
D. the central bright fringe will become a dark fringe.

Answer

To solve the problem, we need to analyze the effects of changing the light source in a Young's Double Slit Experiment from red light to blue light.

### Step-by-Step Solution:

1. **Understanding Wavelength Change**:
- Red light has a longer wavelength compared to blue light. When we change the source from red to blue, the wavelength (λ) decreases.
- **Hint**: Remember that the visible spectrum ranges from red (longer wavelength) to blue (shorter wavelength).

2. **Fringe Width Calculation**:
- The fringe width (β) in a Young's Double Slit Experiment is given by the formula:
\[ \beta = \frac{\lambda D}{d} \]
where:
- \( \lambda \) = wavelength of light
- \( D \) = distance from the slits to the screen
- \( d \) = distance between the slits.
- Since \( \lambda \) decreases when changing from red to blue, the fringe width \( \beta \) will also decrease.
- **Hint**: A smaller wavelength results in a smaller fringe width.

3. **Effect on Consecutive Fringes**:
- As the fringe width decreases, the distance between consecutive bright or dark fringes also decreases. This means that the fringes will come closer together.
- **Hint**: Think about how the spacing between the fringes is affected by the wavelength.

4. **Number of Maxima**:
- The number of maxima (bright fringes) that can fit on the screen increases as the fringe width decreases. This is because with smaller fringe width, more fringes can fit within the same distance on the screen.
- **Hint**: More closely spaced fringes mean that more of them can fit in the same length.

5. **Conclusion**:
- Therefore, the correct options are:
- The consecutive fringes will come closer (Option B).
- The number of maxima formed on the screen increases (Option C).

### Final Answer:
The correct options are B and C:
- The consecutive fringes will come closer.
- The number of maxima formed on the screen increases.