Question

How does the diffraction band of blue light look in comparison with the red light?

• A. No changes
• B. Diffraction pattern becomes narrower
• C. Diffraction pattern becomes broader
• D. Diffraction pattern disappears

Answer 1

The correct option is B

Diffraction pattern becomes narrower

Explanation:

1. In single slit diffraction, the angular width of the diffraction pattern: $\sin \theta =\frac{\lambda }{b}$, where $\theta =$angle from the center of the wall to the dark spot, $\lambda =$wavelength of light, and $b=$width of the slit.
2. The wavelength lowers as blue light takes the place of red light, which causes the fringe width to contract and the pattern to become more pronounced.
3. The angular breadth of the diffraction pattern is smaller when blue light is employed because its wavelength is shorter than that of red light. Consequently, the diffraction pattern narrows.

Hence, the correct answer is option (B).