Waves Flashcards
What happens when waves travel through medium
- particles of medium oscillate + transfer energy between each other
- particles stay in place
Types of wave
- transverse
- longitudinal
Transverse waves
Oscillations perpendicular to direction of energy transfer
Longitudinal waves
Oscillations parallel to direction of energy transer
Oscillations
When a particle moves up/down or side to side undisturbed back and forth from rest
Compressions in longitudinal waves
Regions of high pressure due to particles being close together
Rarefactions in longitudinal waves
Regions of low pressure due to particles being spread further apart
Mechanical waves
Waves that can only travel through a medium
Electromagnetic waves
Waves that can travel through a vacuum or medium
Amplitude
Maximum displacement of a point on a wave away from its undisturbed position
What does amplitude affect
Wave intensity
Unit of amplitude
Metres (m)
Wavelength
Distance from a point on one wave to equivalent point on adjacent wave
Unit of wavelength
Metres (m)
Frequency
Number of waves passing a point each second
What does frequency affect
- pitch in sound
- colour in light
Unit of frequency
Hertz (Hz)
What is a hertz
1 wave passing a certain point per second
Period
Amount of time it takes for a full cycle of a wave
Unit of period
Second (s)
Wave speed
Speed at which energy is transferred through a medium
Practical - measuring speed of ripples on a water surface
- set up beater just touching surface of water
- set vibration generator to low frequency to get steady wave pattern
- put ruler at 90° to ripple tank, measure length 10 waves cover, divide by 10 for 1 wavelength
- mark point on paper, start stopwatch, count how many waves pass in 10 seconds, divide by 10 for waves per second
- wave speed = wavelength x frequency
Electromagnetic waves
Transverse waves that transfer energy from the source of waves to absorber
What do EM waves form
Continuous spectrum
Speed of all EM waves in vacuum
3x10⁸ m/s
What can happen when wave meets a boundary
- absorbed by second material - wave transfers energy to material’s energy stores
- transmitted through second material - wave travels through material, leading to rarefaction
- reflection - incoming ray sent back away from second material
What determines what happens when wave meets boundary
- wavelength of wave
- properties of material
How are EM waves ordered
- long to short wavelength
- low to high frequency
EM spectrum
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- x-rays
- gamma rays
Which EM waves can eyes detect
Visible light
Which EM waves are more dangerous
- short wavelength
- high frequency
Why can EM waves travel through vacuum
Not vibrations of particles but electric + magnetic fields
Variation in wavelengths of EM waves
10⁻¹⁵m to 10⁴m
Why is there range of frequencies in EM spectrum
Waves generated by variety of changes in atoms and their nuclei
What produces radio waves
Oscillating charges in electrical circuits
What determines frequency of radio waves
Frequency of alternating current
Transmitter
Object that charges oscillate in to create radio wave
