A grating has 460 rulings/mm. What is the longest wavelength for which there is a 6.0th-order diffraction line

λ = 3.62 x 10⁻⁷ m = 362 nm

Explanation:

The grating equation gives the relationship between the wavelength, the diffraction line order and the diffraction angle. The grating equation is written as follows:

mλ = d Sinθ

where,

m = order of diffraction = 6

λ = longest wavelength = ?

d = 1/(460 rulings/mm)(1000 mm /1 m) = 2.17 x 10⁻⁶ m/ruling

θ = Diffraction angle = 90° (for longest wavelength)

(6)λ = (2.17 x 10⁻⁶ m/ruling) Sin 90°

λ = (2.17 x 10⁻⁶ m/rulings)/6

λ = 3.62 x 10⁻⁷ m = 362 nm

a.   mass number from atomic number