Waves Flashcards

What do all waves transfer?

Energy; waves do not transfer matter.

Wavefront

A line that joins all adjacent points that are at the same stage of their wave cycle at a given time (the top of the wave).

What is amplitude?

The maximum displacement of a particle from its undisturbed equilibrium position (measured in metres, m).

What is wavelength?

The distance from a point on one wave to the equivalent point (crest/trough) on the adjacent wave (measured in metres, m).

Define frequency.

The number of complete waves passing a single point per second (measured in hertz, Hz).

Define time period.

The time taken for one complete wave cycle to pass a fixed point (measured in seconds, s).

What defines a transverse wave?

The direction of oscillations is perpendicular (at right angles) to the direction of energy transfer.

What defines a longitudinal wave?

The direction of oscillations is parallel to the direction of energy transfer.

Give examples of transverse waves.

Any EM wave.

Give an example of a longitudinal wave.

Sound waves

Can longitudinal waves travel through a vacuum? Why or why not?

Longitudinal waves require a medium (particles) to oscillate and collide to transfer energy. A vacuum has no particles.

State the formula linking wave speed, frequency, and wavelength.

Wave speed = frequency x wavelength

State the formula linking frequency and time period.

Time period = 1/frequency

What is the Doppler Effect?

The apparent change in the observed frequency and wavelength of a wave when the source is moving relative to an observer.

Describe what an observer experiences when a wave source moves toward them.

The wavefronts compress, causing the observed wavelength to decrease and the observed frequency to increase (higher pitch).

Describe what an observer experiences when a wave source moves away from them.

The wavefronts spread out, causing the observed wavelength to increase and the observed frequency to decrease (lower pitch).

State the Law of Reflection.

The angle of incidence equals the angle of reflection measured from the normal.

What happens to a wave's speed, wavelength, and frequency when it enters a denser medium?

Its speed decreases, its wavelength decreases, it bends towards the normal, but its frequency remains constant.

State the order of the EM Spectrum from longest wavelength to shortest wavelength.

Radio waves, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, Gamma rays.

What properties do all electromagnetic waves share?

They are all transverse waves, all travel at the speed of light (3 × 10⁸ m/s) through a vacuum.

State the use and hazard of Microwaves.

Use: Cooking food / satellite transmissions. Hazard: Internal heating of body tissues.

State the use and hazard of Infrared.

Use: Heaters / night vision. Hazard: Skin burns.

State the use and hazard of Ultraviolet (UV).

Use: Tanning lamps / security marks. Hazard: Skin cancer / blindness (ionising).

State the use and hazard of X-rays.

Use: Medical imaging. Hazard: Mutation of cells / cancer (highly ionising).

State the use and hazard of Gamma rays.

Use: Sterilising medical equipment / cancer treatment. Hazard: Highly ionising and penetrating; causes cell mutations.