The secondorder image formed by a diffraction grating having

The second-order image formed by a diffraction grating having 6000 lines/cm is observed at an angle of 29.0 degree. What is the wavelength of the light used?

Solution

d = 1/ 6000 lines/cm

d = 1.67 * 10^-6 m

lambda = d sin theta / m

= (1.67 * 10^-6 * sin 29) / 2

= 405 nm