9702 · 8.2
Diffraction flashcards
Revision flashcards for Cambridge 9702 Diffraction (syllabus 8.2). Flip, recall, then mark a real past-paper question.
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Define diffraction.
The spreading of a wave as it passes through an aperture or around an obstacle.
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When is diffraction most noticeable?
When the wavelength of the wave is similar in size to the gap or obstacle.
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What does a single-slit diffraction pattern look like?
A central bright fringe flanked by alternating dimmer bright and dark fringes.
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Key characteristic of the central bright fringe in single-slit diffraction?
It is approximately twice the width of other bright fringes and has the highest intensity.
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What is a diffraction grating?
A component with many equally spaced, parallel slits.
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How do diffraction grating patterns differ from double-slit patterns?
They are sharper, brighter, and allow for more accurate measurements.
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State the formula for diffraction grating maxima.
$d \sin \theta = n\lambda$
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What does 'n' represent in the grating formula?
The order of the maximum; $n=0$ is central, $n=1$ is first order, etc.
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How does increasing wavelength affect the diffraction pattern?
A larger wavelength causes the pattern to spread out more, resulting in larger diffraction angles.
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Why is there a maximum order of diffraction ($n_{max}$)?
Because $\sin \theta$ cannot be greater than 1, meaning $n\lambda/d$ cannot exceed 1.
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Name one application of diffraction gratings.
Analysing stellar spectra for elemental identification or X-ray crystallography for atomic spacing.
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What happens to the intensity of fringes in a single-slit pattern?
The intensity decreases rapidly with increasing distance from the central maximum.