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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.

Refractive Index of Air

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.

Calculating the critical angle

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.

Radio waves

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.

frequency

= 1 / period

wave speed

= wavelength / period

wave speed

= wavelength x frequency

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