GCSE Physics AQA - Waves

Transverse waves

The vibrations are at right angles to the direction of travel.

Longitudinal waves

The vibrations are along the same direction as the direction of travel.

Examples of transverse waves

Light and other types of electromagnetic radiation, as well as water waves and S waves (a type of seismic wave).

Examples of longitudinal waves

Sound waves and waves in a stretched spring, and P waves.

Equation linking time, period and frequency

Period = 1/frequency

Equation linking wave speed, frequency and wave length

Frequency = wave speed/wave length

The range of human hearing

20 to 20,000 hertz.

Amplitude

The maximum displacement of points on a wave, from a crest or trough to the middle.

Unit of frequency

Hertz (Hz)

What wavelength is measured in

Metres (m)

The frequency of a wave

The number of waves passing a point in a certain time.

Crest

The highest point on a wave.

Wavespeed

How far the wave travels in a certain time. (Sometimes called the velocity of a wave).

Trough

The lowest point of a wave.

Wavelength definition

The distance from any point on one wave to the same point on the next wave along.

Where on a wave the wavelength is found

From the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough.

Where on a wave the amplitude is found

The vertical distance between the middle of a wave and the crest.

Equation for magnification

magnification = image height/ object height

Time period

How many seconds it takes for one complete wave to pass in a given point.

The unit for time period

Seconds (s)

4 types of wave behaviour

-Interference

-Reflection

-Refraction

-Diffraction

Interference of waves

When two waves overlap.

Reflection of waves

When a wave bounces back from a surface instead of passing

through it.

Diffraction of waves

The spreading out of waves when they pass through a gap, or around an obstacle.

Refraction of waves

The change in direction of waves that occurs when waves travel from one medium to another.

In phase

Points on a wave which are a whole number of wavelengths apart.

The Law of reflection (2 rules)

1) The angle of incidence equals the angle of reflection.

2) The incident ray, the reflected ray and the normal all lie in the same plane.

Cause of refraction

Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction.

P-waves (P stands for primary)

They arrive at the detector first, they are also longitudinal waves.

S-waves (S stands for secondary)

They arrive at the detector of a seismometer second, they are transverse waves.

Electromagnetic waves

Transverse waves that transfer energy from the source of the waves to an absorber.

Electromagnetic wave spectrum

Ion

Electrically charged particles formed when atoms lose or gain electrons.

Ionising radiation

Alpha, beta and gamma radiation are all examples of this, can break molecules into smaller fragments. Damages substances and materials, including those in the cells of living things. The ions themselves can take part in chemical reactions, spreading the damage.

Dose

It is the energy of ionising radiation absorbed per unit mass of any material.

Unit of dose

gray (gy)

- gray per second

- gray per hour

- gray per year