# IGCSE Waves

## 42 terms

### wave

A disturbance that transfers energy from place to place but not matter.

### longitudinal wave

A wave in which the vibration of the medium is parallel to the direction the wave travels.

### transverse wave

A wave that moves the medium in a direction perpendicular to the direction in which the wave travels.

### amplitude

The maximum distance the particles of a medium move away from their rest positions as a wave passes through the medium.

### wavelength

The distance from any point on a wave to an identical point on the next wave.

### period

The amount of time it takes to complete one whole wave cycle.

### frequency

The number of complete waves that pass a given point in a certain amount of time.

### hertz

the unit of frequency. I Hz = 1 s-1.

### reflection

The action of a wave bouncing off an object.

### The Law of Reflection

Angle of Incidence = Angle of Reflection

### normal line

The imaginary line drawn perpendicular to the surface of a mirror or any surface.

### Angle of incidence (i)

The angle formed by the incident ray and the normal.

### Angle of reflection

The angle between the reflected ray and the normal.

### Real image

An image of an object formed at the point where light rays actually meet or converge. This happens looking through a lens.

### Virtual image

An image of an object where light rays do not meet, they diverge. This happens in a mirror.

### Refraction

The bending of a wave caused by a change in its speed as it moves from one medium of one density to another a medium with a different density.

### Angle of refraction

The angle between the refracted ray and the normal.

### Snell's Law

n₁sinθ₁ = n₂sinθ₂

### Refractive Index (n)

The ratio of the velocity of light in a vacuum to that in a medium.

1.00

### How to calculate refractive index when travelling from air to new medium:

n = sin(i) / sin(r)

### Total Internal Reflection

The complete reflection that takes place within a substance when the angle of incidence of light striking the surface boundary is less than the critical angle.

### Critical Angle

The angle of incidence at which the refracted ray is perpendicular to the normal.

1/n = sin C

### Wave front

Lines drawn to represent crests; perpendicular to direction wave is travelling.

### Electromagnetic spectrum

The complete range of electromagnetic waves placed in order of increasing frequency.

### Gamma rays

Electromagnetic waves with the shortest wavelengths and highest frequencies. Used to kill cancer cells.

### X Ray

a type of radiation that can go through many solid substances, allowing hidden objects such as bones and organs in the body to be photographed.

### Ultraviolet Rays

Electromagnetic waves with frequencies higher than visible light, but lower than x-rays. Used to detected forged bank notes.

### Visible light

Electromagnetic waves that are visible to the human eye.

### Infra-Red

This has wavelengths that are longer than visible light, and can be felt as heat.

### Microwaves

Shorter wavelength than radio waves. Used for cooking and communication.

Electromagnetic waves with the longest wavelengths and lowest frequencies. Used for to send television signals.

### Sound Waves

A longitudinal wave consisting of compressions and rarefactions, which travels through a medium.

### Rarefaction

The part in a longitudinal wave where the particles are spread apart.

### Compression

The part in a longitudinal wave where the particles are close together.

### Volume

Depends on the amplitude of the sound wave.

### Pitch

Depends on the frequency of the sound wave.

### Echo

A reflected sound wave.

= 1 / period

### wave speed

= wavelength / period

### wave speed

= wavelength x frequency