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All 13 Flashcards — Diffraction
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Question
What is diffraction?
Answer
The **spreading out** of a wave as it passes **through a gap** or **around an edge**.
Question
When is diffraction greatest?
Answer
When the **gap is about the same size as the wavelength** (gap ≈ λ).
Question
What happens when the gap is much wider than the wavelength?
Answer
Very **little** spreading — the wave carries almost straight on; only the edges curl in.
Question
Same gap: does a longer or shorter wavelength diffract more?
Answer
A **longer** wavelength — it is closer to the gap size, so it spreads more.
Question
Same gap: does a higher or lower frequency diffract more?
Answer
A **lower** frequency — lower frequency means a longer wavelength, which spreads more.
Question
Which kinds of wave can diffract?
Answer
**All** of them — water, sound and light (every wave diffracts).
Question
Why can you hear around a corner but not see around it?
Answer
Sound's wavelength (~1 m) is about the size of a doorway (gap ≈ λ → strong diffraction); light's wavelength is far smaller, so it barely spreads.
Question
What is the wavelength λ of a wave?
Answer
The length of **one full wave** — for example from one crest to the next.
Question
Which equation links a wave's speed, frequency and wavelength?
Answer
$v = f\lambda$ (given in the data booklet). Rearranged: $\lambda = \dfrac{v}{f}$.
Question
Classic diffraction trap?
Answer
Thinking a **higher** frequency spreads more — it's the opposite. Higher frequency → shorter λ → **less** diffraction.
Question
Do waves diffract round an obstacle as well as through a gap?
Answer
**Yes**: they bend into the region behind it, more so for a longer wavelength.
Question
Does a wave's wavelength change when it diffracts?
Answer
**No**: only its direction spreads; the wavefront spacing stays λ.
Question
Sketch: plane waves through a gap about λ wide. What do the wavefronts look like?
Answer
**Circular arcs** spreading from the gap, still one wavelength apart.
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Topic 3.3 hub
Wave phenomena
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