WAVES

what is wavelength

distance from one peak to the next

frequency

how many completed waves per second, Hz

what is amplitude

height of wave from rest to crest

wavelength

represent single wave, shows wave from above

time period

time taken for a single wave to pass a point

transverse waves

transerve waves vibrate PERPENDICULAR to direction of energy transfer

• can exist as electromagnetic waves

• can move through vacuum

examples; ripples surface water, electromagnetic waves

longitudinal waves

longitudinal waves travel PARALLEL to the direction of energy transfer

• CANNOT move through vacuum

• sound waves

true or flase; all waves transfer energy without transferring matter

true

what do both transverse and longitudinal waves do:

1. both reflect and refract

2. both transfer energy

doppler effect if stationary;

wave speed is constant → constant frequency and equally spaced sound waves

doppler effect is object is moving from or away from you

if an object is moving towards you, the wavefront get compressed so the sound increases in frequency

→ sound higher pitched than stationary

if an object is moving away from you, the wavefront get stretched out do the sound decreases in frequency

→ sound lower pitched than stationary

common vs differences of electromagnetic waves

• all transverse waves

• travel at same speed through vacuum

.different colors of visible light depend on wavelength———→ increasing frequency, decreasing wavelength

uses of radio waves

wireless communication, radio

uses of microwaves

mobile phone communication, cooking

uses of infrared

heaters and night vision equipment

• emitted by all objects, but hotter more

uses of visible light

opitical fibres and photography

• fibre optic communication, bounces waves off sides of very narrow core, reflected again amd again - used for medical to see inside the body

• focuses light onto lens

uses of ultraviolet

fluorescent lamp - more energy efficient

• absorb and remit it as visible light

uses of X rays

to see internal strctures

• pass through tissue but absorbed by bones

uses of gamma rays

sterilising food and medical equipment

dangers of electromagnetic waves

when em radiation enters tissue it passes through, but some can be absorbed and causes heating of cells and can cause cancerous changes

higher frequency → more danger

why are microwaves dangerous;

• they have a similar frequency to vibrations of many molecules, amd can increase vibrations

• results in INTERNAL HEATING OF BODY TISSUE

→ ovens have shielding

why are infrared waves dangerous

• high frequency, carries more energy than microwaves if exposed too much SKIN BURNS

→ insulating materials

dangers of ultra violet

• DAMAGES SURFACE CELLS, BLINDNESS

• some frequencies are ionisaing

suncream

why are gamma rays dangerous

• very high frequency, ionising - can lead to CELL MUTATION AND CANCER

keep in lead lined boxes

what is law of reflection

angle of incidence = angle of reflection

• occurs when wave hits boundary between two media and doesnt pass through it

what does refractive index show

how fats light travels in material

when does TIR occur

when angle of incidence is greater than critical angle, and no light leaves medium

2 uses of TIR

1. optical fibres. central core surrounded by cladding with lower refractive index

→ core so narrow always hits cladding at amgles higher than C

2. prisms

→ used to see things not in line of sight, light tarvels into one prism then 90 down

LIGHT TRAVELS PARALELL, but diff height to og path