In the phenomenon of diffraction of light, when blue light is used in the experiment instead of red light , then

Options

A. Fringes will become narrower
B. Fringes will become broader
C. No change in fringe width
D. Fring will disappear

Answer

To solve the problem regarding the diffraction of light when blue light is used instead of red light, we can follow these steps:

### Step 1: Understand the Concept of Diffraction
Diffraction is the bending of light waves around obstacles and the spreading of light waves when they pass through a narrow aperture. The pattern produced on a screen consists of bright and dark fringes.

### Step 2: Identify the Wavelengths of Blue and Red Light
- Red light has a longer wavelength (approximately 620-750 nm).
- Blue light has a shorter wavelength (approximately 450-495 nm).

### Step 3: Relate Wavelength to Fringe Width
The width of the fringes in a diffraction pattern is inversely proportional to the wavelength of the light used. This means:
- As the wavelength decreases, the fringe width becomes narrower.
- As the wavelength increases, the fringe width becomes broader.

### Step 4: Calculate the Effect of Changing Wavelength
When blue light (shorter wavelength) is used instead of red light (longer wavelength):
- The fringe width will decrease because blue light has a shorter wavelength than red light.

### Step 5: Conclusion
Thus, when blue light is used in the diffraction experiment instead of red light, the fringes will become narrower.

### Final Answer
The fringes will become narrower when blue light is used instead of red light.

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