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Physics Online
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These resources have been reviewed and selected by STEM Learning’s team of education specialists for factual accuracy and relevance to teaching STEM subjects in UK schools.
Waves - diffraction gratings
This video begins by asking the question, “why do we see rainbow colours on the surface of a DVD?”.
Light from a laser is shone through a diffraction grating to demonstrate a diffraction pattern. The terms 0th, 1st and 2nd order maxima are introduced and explained using the formula dsinθ = nλ. Each symbol is defined.
Returning to the DVD problem, the same formula is used to demonstrate how white light, which contains different wavelengths of light (colours), is diffracted by different amounts (angles). Because λ is proportional to sinθ, the larger the wavelength the greater the angle of diffraction, hence the components of white light spread out when diffracted.
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