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Consider the following information:

Waves are disturbances that propagate energy through a medium. Propagation of the energy depends on interactions between the particles that make up the medium. Particles move as the waves travel, but there is no net motion of particles. Thus, mechanical waves require matter through which to propagate. These waves are of the following types: 

Longitudinal waves: Movement of the particles is parallel to the direction the wave travels; that is, the direction of displacement is the same as the direction of propagation. Sound waves are longitudinal waves. 

Transverse waves: Movement of the particles is perpendicular to the direction the wave travels; that is, the direction of displacement is perpendicular to the direction of propagation. Movement of a wave through a stretched rope or a trampoline is an example of this type of wave. 

Wavelength (λ) is the distance between identical points in the adjacent waves such as from crest to crest or trough to trough. It is measured in meters. 

Frequency (f) describes the number of waves that passes a fixed place in a given amount of time. It is measured in hertz or cycles/s.

A period (T) is the time needed for one complete cycle of vibration to pass through a given point.  Frequency (f) and period (T) have a reciprocal relationship that can be expressed mathematically as:

T = total time / number of cycles

→ T = 1 / frequency = 1 / f

The wave equation states the mathematical relationship between the speed (v) of a wave and its wavelength (λ) and frequency (f):

Speed = wavelength x frequency

→ v = λ x f 

Or:

V = f / T since λ = 1 / f

The amplitude (A) of a wave refers to the maximum amount of displacement of a particle of the medium from its rest position

A swing completes a back-and-forth cycle every 2 seconds. What is the frequency of the swing?

Explanation

Frequency refers to the number of occurrences of a periodic event over time and is measured in cycles per second. In this case, there is one cycle per 2 seconds, so the frequency is 1 cycle/2 s = 0.5 Hz. Choice A is correct.

 

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