Question

What changes are observed in a diffraction pattern if the whole apparatus is immersed in water?

(a) The Wavelength of light increases

(b) Width of central maximum increases

(c) Width of central maximum decreases

(d) Frequency of light decreases

The question was posed to me by my college director while I was bunking the class.

I'd like to ask this question from Diffraction of Light topic in section Diffraction of Engineering Physics II

Answer 1

Right option is (c) Width of central maximum decreases

For explanation I would say: As the whole apparatus is now immersed in water, the wavelength of the light will change.

λ’=\(\frac{\lambda}{\mu}\)

Therefore, as the refractive index of water is greater than the air, the wavelength of light will decrease.

Width of central maxima = \(\frac{2\lambda}{a}\)

Therefore, as the wavelength decreases, the width of the central maxima decreases.