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WAVES - Coggle Diagram
WAVES
ALL waves have
Wavelength, Frequency, Amplitude and Speed
Wavelength (λ) - the distance from one peak to another peak
Frequency (f) - How many complete waves there are
per second
.
Frequency is measured in hertz (Hz). 1Hz is 1 wave per second
Frequency = 1 / Time
Amplitude - The height of the wave (from trough to crest)
Speed (v) - how fast the wave is.
Wave speed = Frequency x Wavelength
Speed (
m/s
) = Freq (
Hz
) x Wavelength (
m
)
Example
: find the frequency of a light wave with wavelength 1 x 10^-7 m. Speed of light = 3 x 10^8 m/s.
Frequency = Speed / Wavelength
Freq = (3 x 10^8) / (1 x 10^-7) = 3 x 10^15 Hz
There are
2
basic types of waves
TRANSVERSE
WAVES
Most waves are transverse, such as
light waves
,
electromagnetic (EM) waves
and
ripples
on water
Electromagnetic (EM) waves
Uses of EM Waves
Radio waves are mainly used for communications
such as TV and radio broadcasting. Long radio waves can be transmitted a long way due to them being bent around the curved surface of the Earth. Moreover, Short wave radio signals can also be received at long distances from the transmitter as they reflect from the ionosphere (a layer of the Earth's atmosphere).
Danger - high levels of radio wave absorption can lead to burns and body tissue damage.
Microwaves are used for satellite communication,
emitted by microwave transmitters/mobile phones. They are also used for
cooking food
and is emitted by microwave ovens.
Danger - Exposure to high microwave radiation can lead to burns and can cause your water molecules to oscillate and heat up.
Infrared radiation is used for heating and to monitor temperatures
. Infrared is given out by all hot objects - the hotter the object, the more infrared radiation is emitted.
Danger - Can burn you
Visible light is used for seeing the world, photography
, etc and is emitted by the sun. Furthermore, it
can be used for communication
through
optical fibres
, which carry data over long distances as pulses of light.
Optical fibres
- they work by bouncing waves off the sides of a narrow core. The light ray enters the fibre at a certain angle at one end and is reflected again and again throughout the fibre until it reaches the end.
Danger - High visible light can burn your skin and hurt your eyes
Ultraviolet is used in fluorescent lamps and security
, which are emitted by UV lamps as well as the sun. Moreover, they are also used in
tanning beds.
Danger - Ultraviolet can cause cell mutation in skin (skin cancer) and can damage your retina and cause burning (high UV)
X-Rays allow us to view the internal structure
of objects and materials, including our
bodies
. X-rays help diagnose broken bones as they are unable to pass through dense materials such as bones and metals.
Danger - A person exposed to x-rays have a small chance of getting cancer.
Gamma radiation can kill living cells
i.e cancer cells and
bacteria/sterilising
and are emitted by radioactive isotopes.
Danger - Gamma rays can cause cancer by cell mutation
ALL
electromagnetic waves travel at the speed of light -
3 x 10^8
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The vibrations in transverse waves are perpendicular to the direction energy is transferred by the wave (vibrations up and down)
LONGITUDINAL
WAVES
insert image
The vibrations in longitudinal waves are parallel to the direction as the wave transfers energy
Some examples of longitudinal waves are: Sound waves, ultrasound waves.
Sound Waves
Because sound waves are caused by vibrating particles, the
denser
the medium, the
faster
the sound travels
through it. They generally travel faster in solids than in liquids, and faster in liquids than in gases.
Sound waves are reflected by hard, flat surfaces at the angle the wave approaches the surface.
Objects like carpets and curtains absorb sound waves instead,
Sound waves also
reflect (change direction)
as they enter different media. As they
enter denser material
, such as from air to water, they
speed up
.
insert image
An oscilloscope can display sound waves. Sound waves can be picked up by a microphone.
The
greater the amplitude
of a wave, the more energy it carries, thus
the louder the sound wave.
Reflection and refraction of waves
Reflection
- all waves can be reflected and occurs when light bounces off a surface.
When light reflects from an uneven surface, the light reflects off at all different angles, resulting in a diffuse reflection.
When light reflects from an even surface e.g a plane mirror, light is reflected at the same angle, resulting in a clear reflection.
Refraction
occurs when a wave slows down or speeds up at a boundary between two materials.
EM waves
travel
slowly
in
denser
media, whereas,
sound waves
travel
faster
in
denser
substances.
If the wave hits the boundary 'face on', it slows down and carries on in the same direction.
If the wave hits the boundary at an angle, the part of the wave that hits the denser layer first slows down.
Angle of incidence = Angle of reflection
