Question

            A grating has 600 lines per mm and is illuminated norn1ally by light of wavelength 590nm.

            (a.) Find the direction of the first-order diffraction image.

            (b.) Is it possible to obtain a third-order image with this diffraction grating for this wavelength?

            (c.) What would be the effect on the number of orders, if the wavelength of the wave is increased?

Answer 1

Given,

Diffraction granting=600 lines per mm

wavelength of light = 590nm

We know that, $d\sin\theta_m = m\lambda$

Here m = 1

$\Rightarrow \sin\theta_m=\frac{\lambda}{d}$

$\Rightarrow \sin\theta_m=\frac{590\times 10^{-9}m\times 600}{1\times 10^{-3}}$

$\Rightarrow \sin\theta_m=354\times 10^{-3}$

$\Rightarrow \sin\theta_m = 0.354$

b) Yes, it can be obtained.

c) If wavelength of the wave get increase then the number of order will get decrease.