Diffraction gratingsEdexcel International A Level Physics: Mind map

Exam questions on Diffraction gratings

1. A student shines a red laser beam of wavelength 633 nm at normal incidence on a diffraction grating that has 300 lines per millimetre. A series of bright spots, called maxima, is formed on a distant screen.
   Calculate the highest order of maximum that can be seen on the screen.2 marks
2. White light containing wavelengths from 400 nm (violet) to 700 nm (red) is directed at normal incidence at a diffraction grating with slit spacing 2.00 × 10⁻⁶ m. The light is then observed on a screen a long way from the grating.
   Calculate the angular separation between the first-order maxima for red light of wavelength 700 nm and violet light of wavelength 400 nm.2 marks
3. In Core Practical 6 a student determines the wavelength of light from a laser. She uses a diffraction grating with 600 lines per millimetre at normal incidence, and places a screen 2.50 m from the grating. The first-order maximum is found 1.06 m from the central maximum on the screen.
   Describe how the student should set up the apparatus and take measurements so that she can calculate the wavelength accurately.3 marks