Which of the following best defines frequency in the context of electromagnetic waves?

• A. The distance between two consecutive crests of a wave
• B. The speed at which a wave travels through a medium
• C. The number of wave cycles that pass a given point per unit time
• D. The energy carried by a single photon of the wave

Answer: (C)

Verified step by step guidance

1. Understand that frequency in the context of electromagnetic waves refers to how often the wave cycles occur at a specific point over a period of time.
2. Recall that frequency is defined as the number of complete wave cycles (or oscillations) that pass a given point per unit time, typically measured in hertz (Hz), where 1 Hz = 1 cycle per second.
3. Differentiate frequency from other wave properties: wavelength is the distance between two consecutive crests, speed is how fast the wave travels, and energy relates to the photon but is not the definition of frequency.
4. Recognize that frequency (\( f \)) and wavelength (\( \lambda \)) are related to the speed of the wave (\( v \)) by the equation: \[ v = f \times \lambda \] but frequency itself specifically counts cycles per second.
5. Conclude that the best definition of frequency is 'the number of wave cycles that pass a given point per unit time,' as it directly describes how frequently the wave oscillates.