Red light is generally used to observe diffraction pattern from single slit. If blue light is used instead of red light, then diffraction pattern.

Options

A. Will be more clear
B. Will contract
C. Will expand
D. Will not be visualized

Answer

To solve the question regarding the effect of using blue light instead of red light in a single slit diffraction pattern, we will follow these steps:

### Step 1: Understand the Concept of Fringe Width
The fringe width (β) in a single slit diffraction pattern is given by the formula:
\[ \beta = \frac{D \cdot \lambda}{d} \]
where:
- \(D\) is the distance from the slit to the screen,
- \(\lambda\) is the wavelength of the light used,
- \(d\) is the width of the slit.

### Step 2: Identify the Change in Wavelength
In this scenario, we are changing the light source from red light to blue light. The key point to note is that the wavelength of blue light is shorter than that of red light. For example:
- Wavelength of red light (\(\lambda_{red}\)) is approximately 650 nm,
- Wavelength of blue light (\(\lambda_{blue}\)) is approximately 450 nm.

### Step 3: Analyze the Effect on Fringe Width
Since the fringe width is directly proportional to the wavelength (\(\lambda\)), if we decrease the wavelength (as we do when switching from red to blue light), the fringe width will also decrease. Therefore, we can express this relationship as:
\[ \text{If } \lambda \text{ decreases, then } \beta \text{ also decreases.} \]

### Step 4: Conclusion about the Diffraction Pattern
As the fringe width decreases, the diffraction pattern becomes more closely spaced. This means that the overall diffraction pattern will be contracted when blue light is used instead of red light.

### Final Answer
Thus, when blue light is used instead of red light, the diffraction pattern will be contracted.

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