Question

Diffraction pattern is obtained using red light. What will happen if it is replaced by violet light?

• A. Bands will disappear.
• B. Bands will become narrow
• C. Bands will get spaced apart.
• D. Bands will remain unchanged

Answer 1

Answer: (B)

Bands will become narrow

Answer 2

In the diffraction pattern, the width of the fringe is given as $D \lambda \over d$.

As $\lambda_v < \lambda_r \: \therefore$ the wavelengthdecreases when the red light is replaced by blue. Hence, the width of the fringe decreases and the pattern becomes narrower.