P1.5 Flashcards
Sound waves…
…are vibrations in a medium and cannot travel through a vacuum
What is a mechanical wave?
Vibrations that travel through a substance (cannot travel through a vacuum) - can be traverse or longitudinal
What do waves transfer?
Energy, communications and information
What is a longitudinal wave?
The oscillations are parallel to the direction of energy transfer
What is a transverse wave?
The oscillations are perpendicular to the direction of energy transfer
What is an example of a longitudinal wave?
Sound waves
What is an example of a transverse wave?
Electromagnetic waves
Longitudinal show areas of compression and rarefraction
Compression= squashed together and rarefraction = spread apart
Name the waves in the electromagnetic spectrum
Rapid - radio Monkeys - microwave In - infrared Velvet - visible Underpants - ultra violet eXcrete - X-rays Gummybears - gamma
Radio waves have…
…little energy, low frequency and low wavelength (10 power15)
Gamma waves have…
…most energy, highest frequency & highest wavelength (10 power4)
Waves can be…
…relflected, refracted and diffracted
What is reflection?
Image is formed that is virtual, upright and laterally inverted
The angle of incidence=
The angle of reflection
What is refraction?
The change of direction of a light ray as it passes across a boundary between two transparent substances
What happens to the wave when it goes from air to glass?
It bends towards the normal and slows down
What happens to the wave when it goes from glass to air?
It bends away from the normal and speeds up
What happens to the wave when it goes from air to glass at 90 degrees/along the normal?
It does not refract/carries on at 90degrees
What is the amplitude of a wave?
The height of a wave crest or a wave trough of a transverse wave from the rest position
What is the wavelength of a wave?
The distance of one wave crest to the next wave crest - measured in m
What is the frequency of a wave?
The number of wave crests passing a fixed point every second - measured in hertz
What is the wave speed of a wave?
Wavelength x frequency
What are radio waves used for?
Communications - tv, radio and mobile phone signals
What are microwaves used for?
Cooking and communications - phones and tv
What are infrared waves used for?
Communications - remote controls & optical fibres
What are visible waves used for?
Communications - photography
What are ultra violet waves used for?
Sunbeds & forged bank notes
What are x-Rays used for?
Bone fractures & seeing inside the body
What are gamma rays used for?
Grating cancer & sterilising equipment
What are reflected sound waves known as?
Echos
What affects the pitch of a note?
The frequency of a wave
What affects the volume of a wave?
The amplitude of the wave
What is diffraction?
The spreading of waves when they pas through a gap or around the edge of an obstacle which has a similar size as the wavelength of the waves
What is the Doppler effect?
The change of wavelength and frequency of a wave (light from galaxies, sounds or microwaves) as it moves towards or away from the observer
What is red-shift?
The movement of a wave towards the red end of the spectrum so the wave moves away from the observer - increased wavelength and decreased frequency
What is blue-shift?
The movement of a wave towards the blue end of the spectrum so the wave moves towards the observer - decreased wavelength and increased frequency
Red shift =
Evidence the universe is expanding
Red-shift of galaxies?
Light from distant galaxies are moving away from us so have an increased wavelength and decreased frequency - the light appears more red
What does the further away the distant galaxies tell us about them?
The faster the galaxies are moving and the bigger increase in wavelength
What is the Big Bang theory?
The theory the universe started from a very small initial point
What is cosmic microwave background radiation?
Electromagnetic radiation which fills the universe. It comes from the radiation present after the Big Bang so provides evidence for the Big Bang theory
What are electromagnetic waves?
Electric or magnetic disturbances that transfer energy from one place to another.
They travel through a vacuum at the same speed (3000000km/s = speed of light)
What is the problem with using your mobile phone a lot (especially near you head)?
Microwaves are transferred between your phone and the bearest transmitter
Some wavelengths of microwaves are absorbed by water and heats it up so this happens with the water in your cells and so lead to damaged health but there’s no evidence yet
