General properties of waves Flashcards – Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028)

What is a wave?

A travelling disturbance that transfers energy without an overall transfer of matter.

How do parts of a rope or spring move as a wave travels along it?

They vibrate around their equilibrium positions while the disturbance travels along the material.

What is a wavefront?

A line joining points on a wave that are at the same stage of vibration.

What is the wavelength, $\lambda$, of a wave?

The distance between successive points at the same stage of vibration, such as adjacent crests.

What distinguishes a crest from a trough?

A crest is a point of maximum displacement above equilibrium; a trough is a point of maximum displacement below equilibrium.

What is the amplitude of a wave?

The maximum displacement from equilibrium.

What is wave frequency, $f$, and what unit is it measured in?

The number of complete vibrations passing a point per second, measured in hertz.

What is wave speed?

The distance the disturbance travels per unit time.

What equation relates wave speed, frequency and wavelength?

$v = f\lambda$

How can frequency be calculated from wave speed and wavelength?

$f = \frac{v}{\lambda}$

How can wavelength be calculated from wave speed and frequency?

$\lambda = \frac{v}{f}$

What are the units of wave speed, frequency and wavelength?

Wave speed: metres per second; frequency: hertz; wavelength: metres.

How is the direction of vibration related to the direction of propagation in a transverse wave?

The vibration is at right angles to the direction of propagation.

What three types of waves can be modelled as transverse waves?

• Electromagnetic radiation
• Water waves
• Seismic S-waves (secondary waves)

How is the direction of vibration related to the direction of propagation in a longitudinal wave?

The vibrations are parallel to the direction of propagation.

What are compressions and rarefactions in a longitudinal wave?

Travelling regions where the material is respectively more compressed and less compressed.

What are two examples of waves that can be modelled as longitudinal waves?

Sound waves and seismic P-waves (primary waves).

What is wave reflection?

A wave meets a surface and returns into the region from which it came.

What is the law of reflection at a plane surface?

The angle of incidence equals the angle of reflection. Both angles are measured from the normal to the surface.

What is observed when straight water waves meet a straight barrier in a ripple tank?

Reflected wavefronts show that the waves change direction at the barrier.

What is wave refraction?

A change in a wave’s direction caused by a change in its speed as it enters a different region.

How does the angle of incidence affect refraction when a wave’s speed changes at a boundary?

At an angle, the wave changes direction. At normal incidence, its direction stays the same.

When a wave’s speed changes at a boundary, what happens to its frequency and wavelength?

Its frequency stays the same, while its wavelength changes.

How does water depth affect the speed of waves in a ripple tank?

Water waves travel more slowly in shallower water.

What is wave diffraction?

The spreading of waves as they pass through a gap or around an edge.

What determines the amount of wave diffraction?

The wavelength relative to the size of the gap or obstacle.

When is diffraction through a gap especially noticeable?

When the gap width is comparable to the wavelength.