Question

A diffraction pattern is obtained using a beam of red light. What happens if the red light is replaced by blue light?

• A. Bands disappear
• B. No change
• C. Diffraction pattern becomes narrower and crowded together
• D. Diffraction pattern becomes broader and further apart

Answer 1

The correct option is C Diffraction pattern becomes narrower and crowded together

The width of the fringe in diffraction pattern is given as $\frac{D\lambda }{d}$

Hence when the red light is replaced by blue light, the wavelength decreases which means that the fringe width decreases and pattern becomes narrower and crowded together.