Question

Blue light, which has a wavelength of about 475 nm, is made to pass through a slit of a diffraction grating that has 425 lines per mm and forms a first-order bright band.

What is the angle of diffraction? Round answer to the nearest whole number.

°

Answer 1

d = 1/(425 mm⁻¹) = 1/425 × 10⁻³ m = 2.3529×10⁻⁶ m.
sinθ = mλ/d = (1)(475×10⁻⁹)/(2.3529×10⁻⁶) ≈ 0.202.
θ = arcsin(0.202) ≈ 11.6° ≈ 12° (to nearest whole degree).