Waves (AQA GCSE Physics Triple Paper 2)

What is a wave?

A wave is a disturbance that transfers energy from one place to another without transferring matter.

What are the two main types of waves?

Transverse and longitudinal.

What is the difference between transverse and longitudinal waves?

In transverse waves, oscillations are perpendicular to the direction of wave travel. In longitudinal waves, oscillations are parallel to the direction of wave travel.

Give an example of a transverse wave.

Light waves, water waves, electromagnetic waves.

Give an example of a longitudinal wave.

Sound waves, ultrasound, seismic P-waves.

Define wavelength.

The distance between the same point on two adjacent waves (e.g., crest to crest or compression to compression).

Define amplitude.

The maximum displacement from the undisturbed position.

What is frequency and what is it measured in?

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

What is the wave period?

The time taken for one complete wave to pass a point.

How are frequency and period related?

Period = 1 ÷ frequency.

What does the speed of a wave depend on?

The medium through which it is travelling.

What is the wavefront?

A line that joins all points on a wave at the same phase of motion (e.g., all crests).

What happens when a wave enters a new medium at an angle?

It changes speed and direction – this is called refraction.

Why do waves refract?

Because the wave changes speed when it moves between materials of different densities.

What happens to wavelength and frequency when a wave slows down in a denser medium?

Wavelength decreases, frequency stays the same.

What is reflection?

When a wave bounces off a surface.

What is the law of reflection?

The angle of incidence = the angle of reflection.

What is refraction?

The bending of a wave as it enters a new medium at an angle due to a change in speed.

What is diffuse reflection?

If a surface is rough, diffuse reflection happens. Instead of forming an image, the reflected light is scattered in all directions.

When is diffraction most noticeable?

When the gap size is similar to the wavelength of the wave.

What is absorption in terms of waves?

When wave energy is transferred into the material, usually increasing its thermal energy.

What are electromagnetic (EM) waves?

Transverse waves that transfer energy through a vacuum or medium and travel at the speed of light.

Name the EM spectrum from longest to shortest wavelength.

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

Which part of the EM spectrum has the highest frequency?

Gamma rays.

Which part of the EM spectrum is used in mobile phones and satellite communication?

Microwaves.

What are infrared waves used for?

Thermal imaging, remote controls, heaters, night-vision equipment.

Which part of the EM spectrum is used for sterilising medical equipment?

Ultraviolet light.

What are X-rays used for?

Medical imaging (looking at bones), security scanners.

How can EM waves be harmful to humans?

UV causes skin damage/cancer, X-rays and gamma rays can cause ionisation leading to mutations and cancer.

What happens when light passes from air into glass?

It slows down and bends towards the normal (refraction).

What happens when light passes from glass into air?

It speeds up and bends away from the normal.

Why does a red object appear red in white light?

It reflects red wavelengths and absorbs all others.

What colour does a green object appear under red light?

Black – it absorbs red and reflects no green.

When does total internal reflection occur?

When the angle of incidence is greater than the critical angle and the wave is moving from a denser to a less dense medium.

What are sound waves?

Longitudinal waves that travel through solids, liquids and gases by particle vibrations.

Why can’t sound travel through a vacuum?

Because there are no particles to carry the vibrations.

How does sound travel through a solid?

As a series of vibrations passed between tightly packed particles.

Why does sound travel faster in solids than in gases?

Particles are closer together in solids, so vibrations are transmitted more quickly.

How do microphones work?

Sound waves cause a diaphragm to vibrate

which converts the vibrations into electrical signals.

What is ultrasound?

Sound waves with frequencies above 20,000 Hz.

What are two uses of ultrasound?

Medical imaging (e.g., prenatal scans) and industrial imaging (e.g., detecting flaws in metal).

Why is ultrasound safer than X-rays for medical imaging?

It is non-ionising and does not damage tissues.

What is echo sounding?

Using reflected sound waves to measure depth (e.g., in submarines and mapping the sea floor).

What is seismic wave analysis used for?

To study Earth’s internal structure and detect earthquakes.

What is the difference between P-waves and S-waves?

P-waves are longitudinal and travel through solids and liquids; S-waves are transverse and only travel through solids.

How does the study of seismic waves show that the Earth has a liquid outer core?

S-waves can’t travel through the outer core; this shadow zone proves it’s liquid.

What are the two types of seismic waves:

• P-waves, which are longitudinal waves

• S-waves, which are transverse waves

What are the factors of P-Waves?

	P-waves	S-waves
Type of wave	longitudinal	transverse
Relative speed	faster	slower
Can travel through	solids and liquids	solids only

What are the factors of S-Waves?

	P-waves	S-waves
Type of wave	longitudinal	transverse
Relative speed	faster	slower
Can travel through	solids and liquids	solids only

What is the principal focus of a convex lens?

The point where rays parallel to the principal axis converge after passing through the lens.

What type of lens is used to correct long sightedness?

Convex lens (also called converging lens)

What does a concave lens do to light rays?

It spreads them out (diverges them), making them appear to come from a focal point.

What is the difference between real and virtual images?

Real images can be projected onto a screen; virtual images cannot—they only appear to come from a place.

How do you draw a ray diagram for a convex lens?

Draw one ray parallel to the axis (refracts through the focal point) and one through the centre (continues straight).

What does a magnification value greater than 1 mean?

The image is bigger than the object.

What is the magnification equation?

Magnification = Image height ÷ Object height

What is a characteristic of images formed by concave lenses?

They are always virtual, upright, and smaller than the object.

How does image distance relate to object distance in a convex lens?

Depends on position: beyond 2F = smaller & real; at 2F = same size; between F and lens = virtual & magnified.

What does a convex lens do to parallel rays of light?

It converges them to a point called the principal focus.

In the RP: Investigating reflection, what is the angle of incidence?

The angle between the incident ray and the normal.

In the RP: Investigating refraction, how do you measure the angle of refraction?

Measure the angle between the refracted ray and the normal line using a protractor.

What material causes light to slow down and bend towards the normal?

A denser medium like glass or plastic.

Why is it important to use a ray box with a narrow slit in the required practical?

To produce a clear, thin ray of light that can be measured accurately.

What is the normal line in ray diagrams?

An imaginary line at 90° to the surface where the light ray hits.

What does refraction mean?

Refraction is the bending of light as it passes from one material into another with a different density.

What safety precaution should you take during the refraction RP?

Turn off the ray box when not in use to avoid burns and overheating.