A grating whose slits are 3.2x10^-4 cm apart produces a third-order fringe at a 25.°0 angle. What is the wavelength of light that is used?

The light used has a wavelenght of 4.51*10^-7 m.

Explanation:

let:

n be the order fringe

Ф be the angle that the light makes

d is the slit spacing of the grating

λ be the wavelength of the light

then, by Bragg's law:

n*λ = d*sin (Ф)

λ = d*sin (Ф) / n

λ = (3.2*10^-4 cm) * sin (25.0°) / 3

= 4.51*10^-5 cm

≈ 4.51*10^-7 m

Therefore, the light used has a wavelenght of 4.51*10^-7 m.