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What is a wave?
The transfer of energy
What two types of wave are there?
Longitudinal and transverse
Give an example of a transverse wave
Water ripples or any electromagnetic wave
Give an example of a longitudinal wave
Sound
What is an area of compression?
Where the particles in a longitudinal wave are close together
What is an area of rarefaction?
Where the particles in a longitudinal wave are more spread out
What two parts of a longitudinal wave are there?
Compression and rarefaction
Does matter move in a wave?
No, matter only oscillates (vibrates), energy moves
What are the four parts of a transverse wave?
Amplitude, wavelength, peak and trough
What is amplitude?
The maximum displacement of a wave away from its undisturbed position
What is wavelength?
The distance between two peaks
What is a peak?
The highest point on a wave
What is a trough?
The lowest point on a wave
What is frequency?
The number of waves passing a point every second
What is frequency measured in?
Hertz (Hz)
What is wave period?
The time taken for one complete wave
What is the equation on the equation sheet that links period and frequency?
Period (s) = 1/frequency (Hz)
Wave speed
the speed at which a wave travels.
How do you calculate wave speed?
Wave speed (m/s) = frequency (Hz) x wavelength (m)
How can you work out speed of ripples on a water surface?
measure the distance travelled and the time taken, speed = distance / time
How can you calculate wavelength on a ripple tank?
Take an image and measure the number of waves in a given space (1m) and divide the distance by the number of waves
What type of waves are all electromagnetic waves?
Transverse
Electromagnetic waves
A continuous spectrum of waves that travel at the same velocity through a vacuum or air
Which electromagnetic waves have the shortest wavelength?
Gamma rays
Which electromagnetic waves have the highest frequency?
Gamma rays
Which electromagnetic waves have the longest wavelength?
Radio waves
Which electromagnetic waves have the lowest frequency?
Radio waves
What is the relationship between wavelength and frequency?
The shorter the wavelength, the higher the frequency
What is the order of the electromagnetic spectrum?
Radio, micro, infrared, visible, UV, X-rays, gamma rays
What is reflection?
Waves bouncing off a material
What is refraction?
The bending of waves as it changes speed crossing between different media.
How are radio waves produces?
produced by oscillations in electrical circuits
What do radio waves create when they are absorbed by an aerial?
they cause the electrons in the aerial to vibrate which creates an alternating current
What 4 electromagnetic waves can be used for communication?
Radio, micro, infrared and visible
What electromagnetic radiation can be ionising?
UV, X-rays and gamma rays
What effect can UV have on skin?
Causes it to age prematurely and tan /burn
What effect can x-rays and gamma rays have on cells?
They cause mutation of genes and cancer
Why are radio waves useful for long distance communication?
They reflect off the ionosphere and diffract over hills with a very long wavelength.
Why are microwaves useful for cooking?
Some wavelengths are absorbed by the water molecules in food, heating it up
Why is infra-red useful for night photography?
It is transmitted from all hot objects and can be used to see things in the dark
Why is visible light useful for communication in traffic signals?
It is detected in our eyes and allows us to see.
Why is UV useful for security notes?
Some substances fluoresce under UV light, allowing security checks.
Why are x-rays great for looking a bones?
They pass through soft tissue, but are absorbed by hard tissues such as bones, allowing us to see them.
Why are gamma rays good for sterilising medical equipment?
Their very small wavelength means that they causes changes in the nuclei of atoms, which kills anything on the medical equipment
What is a wavefront?
a line connecting the crests of a collection of waves, they lie at right angles to the direction the wave is travelling
when a wave slows down the wavefronts .......
get closer together
