8.2 AS Level

Diffraction

7 flashcards to master this topic

Definition Flip

Define diffraction.

Answer Flip

Diffraction is the spreading out of waves as they pass through an aperture or around an obstacle. The effect is most significant when the wavelength is comparable to the size of the aperture.

Key Concept Flip

Describe how the width of a gap affects the amount of diffraction.

Answer Flip

The amount of diffraction is greatest when the gap width is approximately equal to the wavelength of the wave. As the gap width increases relative to the wavelength, the amount of diffraction decreases.

Key Concept Flip

What happens to the diffraction pattern when the wavelength of the wave increases (gap size constant)?

Answer Flip

Increasing the wavelength (for a constant gap size) leads to increased diffraction. The waves spread out more after passing through the gap.

Key Concept Flip

Describe an experiment that demonstrates diffraction.

Answer Flip

Water waves in a ripple tank can be used. Place a barrier with a narrow gap in the tank. When plane waves are directed towards the gap, they will diffract and spread out on the other side.

Key Concept Flip

Explain how the wavelength of water waves relates to the size of the gap needed for significant diffraction in a ripple tank experiment.

Answer Flip

For observable diffraction in a ripple tank, the wavelength of the water wave should be similar to, or larger than, the width of the gap. If the wavelength is significantly smaller, diffraction will be minimal.

Key Concept Flip

Sketch the wave pattern after diffraction through a 'small' gap. Define 'small'.

Answer Flip

Sketch: Semicircular wavefronts emanating from the gap. 'Small' means the gap width is approximately the same size or smaller than the wavelength of the wave.

Key Concept Flip

Sketch the wave pattern after waves pass through a very wide gap (relative to their wavelength).

Answer Flip

Sketch: The waves pass through the gap with minimal bending. The wavefronts remain mostly planar, with slight diffraction effects near the edges of the gap. Most of the wave continues straight.

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8.1 Stationary waves 8.3 Interference