waves

what are transverse waves

transverse waves gave ociliations perpendicular to the direction of energy transfer

• most waves are transverse → electromagnetic waves

what are longitudinal waves

longitudinal waves have ocillations parallel to the direction of energy transfer

• examples are sesmic P waves and sound waves

• when drawing them some regions would be more compresses whilst others are more spread out. This is because the wave is vibrating back and forth

what do all waves do

transfer energy from one place to another

• they DO NOT transfer any matter

what is distance in waves

the distance is how far the wave has travelled from the starting point

what is displacement in waves

how far from equilibrium the wave oscillated (moved up and down)

what is a wavelength

distance of one entire oscillation

how do you calculate wave speed

wave speed (m/s) = frequency (Hz) x wavelength (m)

what is the order of waves

• radio waves (10⁴m-1m) - longest wave length

• microwaves

• infra-red

• visible

• Ultra violet (UV)

• x-ray

• gamma rays (10¹⁵ ) - shortest wave length

what are the two types of micro waves

absorbed by water

not absorbed by water

why are microwaves used for microwaves

lots of food we eat contain water molecules, and the energy from the wave gets absorbed by the microwave

the more the particles vibrate the more they transfer energy to their nieghbouring particles

it then spreads throughout food by convection and conduction

why are microwaves used in satalights

• for communication

  microwaves have to pass through earths watery atmosphere and do not absorb water

what is infrared radiation emitted from

all objects that have thermal energy

• hotter the object the more infra red emitted

what is infra red waves used in

infra red cameras to spot living organisms and see in the dark

also used in cooking→ ovens emit lots of infra red and heat food by transfering heat energy

what is visible light

the light we use to see

• appears in all different colours depending on the wavelength

  -red is the longest wavelength and violet is the shortest wavelength

how is visible light waves used for communication

optical fibers (thin glass or plastic fibers) transmit pulses of light over long distances and light is reflected every time it hits the surface and ends up bouncing

• have to use materials that totally reflect the light so light isn’t scattered

it then emerges the other end of the fiber

can then be interpreted

used to transmit data quickly

what can you use instead of optical fibers

an alternative is copper fibers

• signal less likely to be lost

• transmit more info

what emits ultra violet

the sun so can give sunburn→ damages skin cells used for steralisation

-kills and destroys microorganisms

what is florescent

when UV light is absorbed and remitted as light

how do florescent lights work

• generate UV radiation

• absorbed by a layer of phospherous (coats inside of blub)

• phosphourous re-emits energy as visible light (coverts UV to visible light)

so can be used in security, e.g security pens as it doesnt show UV until light is shown

detects foreign objects

florescent bubls are highly efficient

what are radio waves used for

communication → television and radio

how are radio waves used for communication what

• radio waves are transmitted easily through air and don’t harm the human body if absorbed. They can be reflected to change direction (ideal for communication)

• produced by oscillations in electrical circuits. When absorbed the electrical current has the same frequency as the radio waves.

  Information is then coded into the wave before transmission which can be decoded when the wave is received. Television and radio systems use this to broadcast information

what do all electromagnetic waves do

• transfer energy as radiation from the source of the waves to an absorber

• can travel through a vacuum (300 million meters/second)

what are examples of transverse waves

• ripples on the surface of the water

• electromagnetic waves

• vibrations in a guitar string

• sesmic C waves what

what are examples of longitudinal waves

• sound waves

• sesmic P waves

• ultra sound waves

what are areas of compression in longitudinal waves

regions of high pressure due to particles being close together

what are areas of refraction in longitudinal waves

regions of low pressure due to particles being spread apart

how is radiation dose measured

risk of harm caused by exposing the body to ionising radiation

measured in sieverts (SV)

whats a sievert as a millisievert

1000 mSvwhat

what are examples of back ground radiation

• radioactive rocks in earths crust

• cosmic rays from space

• man-made sources like nuclear weapons fallout and nuclear accidents

what is the level of background radiation and dose effect by

jobs people do and places people live

what wavelengths are the most ionising

short

• they remove or add electrons from molecules, producing electronically charged ions

what hazardous effects can radiation have on the body

• UV rays can cause the skin to age prematurely and increase risk of skin cancer

• x-rays and gamma rays can cause mutation of genes, which lead to cancer