3.3.2.2
Applications of diffraction gratings
Interference & Diffraction — AQA A-Level Physics
- Spectrometers: analyse light from stars to determine chemical composition, measure red shift, and observe emission/absorption spectra.
- X-ray crystallography: X-rays directed at a thin crystal diffract because the atomic spacing is similar to the X-ray wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m).. The diffraction pattern reveals the crystal structure.
- Monochromators: select a specific wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m). from a broad source for analysis.
- Optical fibre wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m). selection: choose the optimal wavelength for transmission.
Examiner Tips and Tricks
- You need to know applications of diffraction gratings but not the specific details of spectrometer apparatus.
- Avoid vague phrases like 'observe spectra'.
- Instead say 'measure the wavelength of light emitted by a star' or 'determine the composition of a star from its absorption spectrumA continuous spectrum with dark lines at specific wavelengths where photons have been absorbed by atoms, exciting electrons to higher energyThe capacity to do work. Measured in joules (J). levels.'.