Question

A parallel beam of white light is incident normally on a diffraction grating. It is noted that the second-order and third-order spectra partially overlap. Which wavelength in the third-order spectrum appears at the same angle as the wavelength of 600 nm in the second-order spectrum?

A. 300 nm
B. 400 nm
C. 600 nm
D. 900 nm
E. 950 nm​

Answer 1

Answer:

option B is correct

Explanation:

explained and solved in the picture.

Answer 2

Answer:

The wavelength in the third-order spectrum is 400nm i.e.option(B).

Explanation:

We will solve the question by the given relation,

$n_1\times \lambda_1=n_2\times \lambda_2$          (1)

Where,

n₁=initial order of the spectra

n₂=final order of the spectra

λ₁=initial wavelength of the spectra

λ₂=final wavelength of the spectra

From the question we have,

n₁=2

λ₁=600nm

n₂=3

By substituting the required values in equation (1) we get;

$2\times 600nm=3\times \lambda_2$

$\lambda_2=\frac{2\times 600nm}{3}$

$\lambda_2=400nm$

Hence, the wavelength in the third-order spectrum is 400nm i.e.option(B).