waves and the electromagnetic spectrum

describe the movemant of longitudional waves and give examples

vibrations of the particles are parallel to the direction of travel

sound waves

compression waves

what way does transverse wave travel and give example

vibrations of particles are perpendicular to the direction of travel

light waves

water ripples

define amplitude of a wave

from rest position to crest or trough

Define the wavelength of a wave.

full cycle of the wave e.g crest to crest

A student watches ripples passing a fixed point on the edge of a lake. The student has a stopwatch.

Describe how the student could determine the frequency of the ripples. (3 marks)

• Use a stopwatch to measure the time taken for a number of waves to pass the fixed point.

• Count the number of waves passing the point.

• Divide the number of waves by the time taken to calculate the frequency.

What happens when frequency changes? in a ripple tank

• Increasing frequency means more waves are produced each second.

• The wavelength decreases if wave speed stays constant.

• Decreasing frequency means fewer waves are produced each second.

• The wavelength increases if wave speed stays constant.

create a method for using a ripple tank to measure the wavelength,frequency and wave speed

• Set up a ripple tank with a shallow layer of water.

• Use a vibrating dipper to produce regular straight waves.

• Shine a lamp above the tank so the wave pattern can be observed.

• Use a ruler to measure the distance across several wavelengths.

• Divide the distance by the number of wavelengths to find one wavelength.

• Count the number of waves passing a fixed point in a measured time to find frequency.

• Calculate wave speed using the wave equation.

electromagnetic spectrum in order

Rabbits Make Ice Very Usually, except Grandma.

• radio

• Microwaves

• Infrared

• Visible light

• Ultraviolet

• X-rays

• Gamma rays

how could electromagnetic waves be dangerous

Radiation	Potential danger
Microwaves	Internal heating of body cells
Infrared	Skin burns
Ultraviolet	Skin damage, skin cancer and eye damage
X-rays	Cell damage and mutations
Gamma rays	Cell damage and mutations

what are the electromagnetic waves used for

Wave	Common use
Radio	Radio and TV broadcasting
Microwaves	Cooking and satellite communications
Infrared	Thermal imaging and heaters
Visible light	Seeing and photography
Ultraviolet	Security marking and sterilising
X-rays	Medical imaging and airport security
Gamma rays	Sterilising medical equipment and cancer treatment

Explain how radio waves allow information to be transmitted from a radio station to a radio receiver.

• The sound (music or speech) at the radio station is converted into an electrical signal.

• The electrical signal is used to produce radio waves in the transmitting aerial. These waves travel to the receiving aerial, causing charges to oscillate and produce an alternating current.

• The radio receiver converts the electrical signal back into sound using a speaker.

why can some waves travel further than others

longer waves can travl further because they can bend around objects and diffract more but shorter waves have shorter wavelengths and diffract less

explain the useage of both microwaves

microwaves without water molecules travel through the earths atmosphere and recieved by a satelite then transmitted back to earth and recieved by a satelight dish

, microwaves heat food because they are absorbed by water molecules inside the food, increasing their internal energy store

explain usages of infared radiation

used in cameras to see in the dark,spot living organisims-the brighter when seen on camera the more infared radiation they emit(warmer)

cooking-heating metal for ovens make the metal emmit loads of infared radiation which heats food by transferring heat energy

electrical heater-uses electrical energy to heat metal which emitts infared radiation to the surroundings

uses of uv

suntan

security marking,special pen that is invisible unless shined on by special pen

flourescent lamps : UV radiation emitted inside light bulb absorbed by a layer of phospher which is re immeted energy as visible light

usage of xray

see internal structure by xray passing through some parts of the body denser areas like bones are completely white but areas that recieve radiiation are black/visible

highly ionising-dangerous

uses of gamma ray

• Cancer treatment: Gamma rays kill cancer cells by damaging their DNA.

• Sterilising medical equipment: Gamma rays kill bacteria and other microorganisms.

Remember: Gamma rays are highly penetrating and are ionising radiation, so they can damage cells.