physics term2

wave

A disturbance or vibration carrying energy through a medium

amplitude

Maximum distance any point in a wave moves from its rest position.

wavelength

distance between 2 corresponding points of a wave; a full cycle. (compression to compression, crest to crest etc)

wave velocity(m/s)=

frequency(Hz) x wavelength(m) or v=λf

strobe light method

A method of finding the wave length.

1)turn on the machine and strobe light.

2)adjust the frequency of the strobe until it appears still.

3)measure the distance covered by 10 strobes with a cm ruler for accuracy.

4)divide the result by 10 to find the average wavelength.

5)you can multiply wavelength and frequency to find wave velocity.

frequency

Number of complete waves/cycles passing a point per second

period

the number of seconds it takes for one full cycle. period=1÷frequency.

crest

Highest point of a wave

trough

Lowest point of a wave

medium

The material wave travels through

mechanical wave

Waves that are caused by vibration.

transverse wave

A mechanical wave in which the particles of the medium vibrate at right angles (perpendicular) to the direction that the wave travels.

Transverse waves transport energy without transporting matter.

Does not need particles to carry the vibration.

longitudinal wave

.A mechanical wave in which particles of the medium vibrate in the same direction that the wave travels.

(back and forth, parallel to the wave direction)

Longitudinal waves transport energy without transporting matter.

Needs particles to carry the vibration.

rarefaction

A decrease in density and pressure in a medium, such as air, especially when caused by the passage of a wave, such as a sound wave.

(low pressure, fewer particles)

compression

A force that tends to shorten or squeeze something, decreasing its volume. ( high pressure, lots of particles)

sound waves

Transfer of energy from a vibrating object in longitudinal waves that travel through matter and are perceived by ears.

It travels in a series of compressions and rarefactions .

The speed depends on the medium through which it is travelling.

echoes

reflected sound waves. (sound waves that hit a hard fat surface).

superposition

• The change from one wave to two.

• When two waves meet, they either add together or cancel each other out. This change of two waves into one wave is called

speed=

distance / time

clap- echoes method

A method of measuring the speed of sound.

1)You stand a long distance from a wall, hit 2 wooden blocks together, start the stopwatch and listen for the echo and then stop the stopwatch.

2)One way to reduce timing errors in this method is to clap in time to the echoes 10 times.

3)This means that the time between each clap is the journey time for the sound.

4)You then measure the time for 10 claps.

5)This time will then be applied to the formula to find speed

velocity

the speed of something

wavelength of a soundwave…

changes, it gets longer when it speeds up, and shorter when it slows down

eardrums

the part of your ear that receives soundwaves and vibrates.

It passes on the vibrations to the ossicles.

ossicles

tiny bones in your middle ear that pass on sound wave vibration through the semi-circular canals and into the cochlea

cochlea

a spiral shaped organ in the middle ear that turns the sound vibrations into electrical signals which gets sent to your brain

the brain then interperates the signals as sound.

auditory nerve

a nerve carrying and connecting electrical signals from the inner ear to the brain.

the brain then interprets the signals as pitches and volumes depending on intensity and frequency.

(example, high frequency=high pitch)

audition

human hearing, it is limited by the size and shape of the eardrums.

older people need sound to be louder to hear because of the wear and tear or the cochlea and auditory nerve over time.

ultrasound waves

sound with a frequency greater than 20,000 Hz and are used to form images of anything in the body that is not surrounded by bone.

(developing foetus’ , liver, kidney etc)

absorption

when after meeting a boundary, the energy being transferred by a wave is taken into an energy store of a material.

(this how a microwave works)

transmission

when meeting a boundary, a wave keeps on travelling through the new material often at a different speed/velocity which can lead to refraction

reflection

when after meeting a boundary, an incoming ray is sent ‘back’ from the new material.

angle of incidence= angle of reflection ALWAYS

normal

an imaginary line that is at a right-angle 90° to the surface at the point the light hits it

reflection of visible light

What allows us to see thing; light bounces off of objects and into our eyes.

scattering

light rays reflect off of a rough surface (paper) in all different directions.

each ray hits surface at a different angle and reflect at that same angle.

specular reflection

light rays reflect off of a smooth surface in all the same direction giving a clear reflection

white light

a mixture of all different colours of light (red, yellow ,green ,blue ,indigo, violet)

each colour has a different wave length.

refraction

 the change in direction of a wave passing from one medium to another caused by its change in speed.

the wave bends towards the normal

if the wave slows down

the wave bends away from the normal.

if the wave speeds up

triangular prisms disperse white light

each colour has a slightly different wavelength, so they refract at different angles which shows a rainbow.

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triangular prism experiment

transverse waves that are vibrations of electric and magnetic fields

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

• can travel through a vacuum such as in space

• travel at the same speed through a vacuum or the air

electromagnetic waves

The complete range of frequencies of electromagnetic waves from the lowest to the highest in order

radio, infrared, visible light, ultraviolet, X-ray, and gamma ray waves

electromagnetic spectrum

an EM wave that has the longest wavelength and lowest frequency of the spectrum.

Is used for communication

can be transmitted through the body without being absorbed.

an EM wave that has the longest wavelength and lowest frequency of the spectrum.

Is used for communication

can be transmitted through the body without being absorbed.

microwaves

an EM wave that has the second longest wavelength an second lowest frequency of the EM spectrum

It is used for communication and cooking

The wavelength of this wave can be absorbed, causing the heating of cells which can be dangerous

infa-red

an EM wave that has the 3rd longest wavelength and 3rd lowest frequency.

It is used increase or monitor temperature

it is mostly reflected or absorbed by the skin, causing some heat.

This wave can cause burns if skin gets to hot.

visible light

an EM wave which is in the middle of the spectrum and the only wave we can see.

It is used for fibre optics and as a light source

It is mostly reflected or absorbed by the skin but is also used as a light source or be concentrated to make a laser

It can damage the retina of your eye.

ultra-violet

an EM wave which has the 3rd shortest wavelength and 3rd highest frequency of the EM spectrum.

It is used in fluorescent lamps

it is mostly absorbed by skin, but has a higher frequency meaning it transfers more energy causing more damage.

could lead to skin cancer, tissue damage, genetic mutations and radiation illness

ionising radiation

When waves that transfer a lot of energy enter living cells, it collides with atoms, knocking of electrons.

x-rays

an EM wave that has the second shortest wavelength and second highest frequency.

it is used to observe the bones and has a very high frequency ,meaning it transfers a lot of energy.

it is also ionising , can cause skin cancer, genetic mutations and can pass through the skin and be absorbed by deeper tissues.

gamma rays

an EM wave which has the shortest wavelength and the highest frequency

It is used to sterilised medical instruments and cancer treatment

It can cause radiation illness, genetic mutations and skin cancer

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