How is the frequency of a wave defined?
AThe distance separating two neighbouring wave crests
BThe height of a crest above the null point
CThe number of wave crests passing a point each second
DThe time a single crest takes to form
Answer & Solution
Correct answer: C. The number of wave crests passing a point each second
1. Frequency is the number of wave crests that pass a fixed point every second.
2. It is expressed in hertz, where one hertz means one crest passing per second.
3. The distance between crests is the wavelength, a separate quantity from this count.
4. The height of a crest above the null point describes amplitude, not frequency.
_Source: OpenStax Physics (CC BY 4.0), Ch 15 "Light", section 15.1 The Electromagnetic Spectrum_
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