Question

A diffraction grating has a spacing of 1.6 * 10^-6 meters. A beam of light is incident normally on the grating. The 1st order maximum makes an angle of 20 deg with the un-deviated beam. What is the wavelength of the incident light?

Answer 1

d sin⁡θ=nλ
1.6 ∙ 〖10〗^(-6) sin⁡20=(1)(λ)
λ=550 nm.