Question

21. A diffraction grating has a spacing of 1.6x10 m. A beam of light is incident normally on the
grating. The first order maximum makes an angle of 20° with the un-deviated beam. What is
the wavelength of the incident light? (sin 20° =0.342)
a. 210 nm b. 270 nm C 420nm
d. 550nm e. 690nm​

Answer 1

Answer:

given = d = 1.6 X 10m

             θ = 20°=0.342

             n = 1

to find = wavelength( λ)

solution :-

apply the,  

               λ =   d sinθ / n  

               λ =  1.6 X 10 X 0.342 / 1

               λ =   0.5472nm≅ 550 nm

so the final wavelenth of incident light is 550nm.

so the option d is correct answer.