P6

Waves = regular patterns of disturbance that transfer energy from one point to another without transferring particles of matter

There are two types of waves...

- longitudinal

- transverse

Longitudinal waves = particles vibrate to and fro

Transverse waves = particles vibrate up and down

Amplitude = maximum disturbance cause by a wave

Wavelength = distance between corresponding points on two adjacent disturbances

Frequency = number of waves produces in one second, measured in hertz

If a wave travels at a constant speed either increasing frequency and decreases wavelength or decreasing frequency and increases wavelength

If a wave has a constant frequency either increasing speed and decreases wavelength or decreasing speed and increases wavelength

Wave spead (m/s) = frequency (Hz) x wavelength (m)

Refraction = waves change direction when they pass between one medium and another

Diffraction = waves spread out from the edges when they pass an obstacle

Reflection = waves are reflected when a barrier is placed in their path

Constructive interference = two waves arrive in step and reinforce each other

Destructive interference = two waves arrive out of step and cancel each other out

Interference pattern = caused when the light from one ray is either in step or out of step with the other ray

Light is reflected when it strikes a surface

Incident ray = light travelling towards a surface

Reflected ray = light travelling away from a surface

Light...

- changes direction when it passes between one medium and another

- continues straight on when it meets a boundary at 90 degrees

Total internal reflection = light is reflected when the angle of refraction is greater than 90 degrees as it cant escape from the medium

Electromagnetic radiations form the electromagnetic spectrum

Visible spectrum = the only part of the electromagnetic spectrum that can be seen

Colours have different frequencies and different wavelengths

Colours are refracted by different amounts as they *** through a prism...

Red light = refracted the least Violet light = refracted the most

Photons = packets of energy

Intensity of beam depends on amount of energy carried by each photon.

Radio and micro waves = travel through Earth's atmosphere and space

Light and infrared waves = travel through optical fibres

Modulation = makes a wave vary in amplitude or frequency to create a variation in the orginal wave.

Analogue signals = vary in exactly the same way as the information they carry.

Digital signals = used two symbols (0 = off and 1 = on) which can be transmitted as a series of pulses.

Digital signals can travel long distances at a higher quality than analogue signals because interference can be removed