White light is incident on a grating. We have to show that no matter what the value of the grating spacing d is, the second and thirdorder spectra will overlap.

Solution: Click For PDF Version The grating equation isThe spread of the visible light in the second and thirdorder spectra will therefore be 2^{nd} order . 3^{rd} order . We note that is not . Therefore, the second and third orders of the white light spectra will overlap irrespective of the grating spacing.
