National 5 Physics - Waves

Wave

transfers energy without any transfer of mass / matter

Transverse wave

a wave that vibrates at right angles to its direction of travel

Longitudinal wave

a wave that vibrates parallel to its direction of travel

Frequency

number of waves produced or passing a point per unit of time

Period

time for one wave to pass a point, the inverse of frequency

Wavelength

distance from a point on one wave to the same point on the next wave, ie crest to crest or trough to trough

Amplitude

distance from the central axis to the crest or trough of a wave.

Wave speed

distance a wave travels per unit of time

Diffraction

the change in direction of a wave as it passes by an obstacle or through a gap

Electromagnetic spectrum

the full range of frequencies of electromagnetic waves

Gamma rays

highest frequency and energy EM waves, detected by photographic film, used for cancer treatment

X-rays

2nd highest frequency and energy waveband, detected by photographic film, used to view broken bones

Ultraviolet

band of EM spectrum with frequency just above visible, causes sun burn, detected using fluorescent materials.

Visible light

part of the spectrum which can be detected by the retina of the human eye, includes the peak wavelengths emitted by the Sun.

Infrared

heat radiation, part of the EM spectrum with lower frequency and longer wavelength than visible, detected by photodiodes and charge coupled devices (CCD)

Microwave

short wavelength radio waves used for mobile phone communication and heating food.

Radio wave

the longest wavelength part of the spectrum, detected using an aerial, used to transmit radio and TV signals.

Refraction

the change in speed and wavelength of a wave as it travels from one medium to another. If the angle of incidence is greater than 0° then this causes a change in direction.

Normal

imaginary construction line drawn at right angles to a surface where a ray of light is incident on it, all angles are measured from the normal

Incident ray

the ray of light going into a surface

Angle of incidence

angle between the normal and the incident ray

Reflected ray

the ray of light which bounces off a surface and travels away from it.

Angle of reflection

angle between the normal and the reflected ray. This is always equal to the angle of incidence

Refracted ray

ray of light which has passed through a surface and is travelling through a different material

Angle of refraction

angle between the normal and the refracted ray

Total internal reflection

occurs when the angle of incidence is greater than the critical angle, light does not refract through a surface but instead reflects off it like a mirror.

Critical angle

the angle of incidence which produces an angle of refraction of 90°

Refractive index

a measure of how much a material slows down a ray of light relative to its speed in a vacuum.