Question

A diffraction pattern is obtained by making blue light incident on a narrow slit. If blue light is replaced by red light then

• A. there is no change in diffraction pattern.
• B. diffraction bands become broader.
• C. diffraction bands disappear.
• D. diffraction bands become narrower.

Answer 1

The Correct Option is B

When blue light is replaced by red light, there will be a change in the diffraction pattern. The behavior of light waves in diffraction depends on their wavelength. Red light has a longer wavelength compared to blue light. 
The phenomenon of diffraction occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. The narrower the slit, the more significant the diffraction effects. 
Since red light has a longer wavelength compared to blue light, it will diffract more when passing through the same narrow slit. This means that the diffraction bands produced by red light will be broader compared to the diffraction bands produced by blue light. 
Therefore, the correct option is (B) diffraction bands become broader.