Types of waves
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 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)
Behaviour of waves and Interference
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
- 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 and Digital and Analogue signals
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