waves Flashcards
longitudinal
oscillations parallel to direction of energy transfer
sound
transverse
oscillations perpendicular to direction of energy transfer
light, water
waves transfer…
energy not matter
amplitude A
distance between rest positions and peak/trough
sound = loudness
light = brightness
wavelength
distance between two identical points on a wave (m)
frequency f
no. complete waves per second Hz
sound = pitch
light = colour
time period T
time for one complete oscillation (secs)
frequency and time period
f = 1/T
velocity v
speed of wave m/s
velocity formula
v= d/t
v = wavelength/ T
v = f x wavelength
peak
highest point on wave
trough
lowest point on the wave
mechanical wave
transfers energy by the vibration of particles - so can’t travel in a vacuum
sound
speed of sound depends on
the medium - where particles are close vibrations get passed on quickest
sounds with freq. above 20kHz
ultrasound
range of human hearing
20 - 20 000 Hz
experiment to measure speed of sound in air
- measure distance to walk
- person1 claps person2 starts stop clock
- person2 stops timing when they hear echo
- use s=d/t
- repeat and average
how boats use ultrasound
use for echolocation
use to see how far things are
- time between sending and receiving pulse recorded
- speed of sound know
use d = s x t/2 to find d
speed of sound in air
330 m/s
ultrasound uses
- imaging foetus
- shattering kidney stones
- clean delicate mechanisms without dismantling them
CRO traces
- set controls so complete wave is on the screen
- amplitude = count squares x volts/div
- time period = squares for one full wave x time base
- freq. = 1/T
oscilloscopes
instrument that portrays waves as traces of light on a screen
signal generator
used with loudspeaker and amplifier to make sounds of large freq. range
similarities between waves in emag. spectrum
- transverse
- travel in vacuum
- travel at speed of light (3x10^8m/s)
- undergo interference (reflect, refract etc.)
longest wavelength wave
radio waves
shortest wavelength wave
gamma rays
lowest freq. wave
radio
highest freq. wave
gamma rays
emag. spectrum
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- x-rays
- gamma rays
gamma ray uses
treating cancer
sterilisation
x-ray uses
medical imaging
airport security
UV uses
security marking
fluorescent tubes
visible light uses
seeing
photograoht
infrared uses
heaters
night vision equipment
microwave uses
cooking
satellite transmissions
radio wave uses
communications
gamma ray dangers
mutation
cancer
kill living cells (ionising radiation)
xray dangers
cancer
cell damage
uv dangers
blindness
cancer
suburn
visible light dangers
damage eyes
infrared dangers
burning of tissues (heat
microwave dangers
heats water within body
damage cells
radio wave dangers
none
law of reflection
angle of incidence is = to angle of reflection
i= r
normal line
line perpendicular to a surface
refraction
when light changes speed and or direction when it passes from one medium to another of diff. density
light speeds
away from normal
light slows
toward normal
light hits surface at 0° to normal
no directionchabge
light bends if
it’s incident at an angke
experiment to measure refractive index of glass
- trace glass block
- shine light from ray box into glass block
- mark ray of light in pencil
- remove block and draw normal line
- measure angle of incidence and reflection with protractor
- repeat several value did i plot graph of sin i (y) and sin r (x)
- gradient is refractive index
refractive index
measure of the light bending ability of a medium
n = sin i / sin r - only light slowing down
TIR
total internal reflection
- when an angle of incidence is great enough light bends so far away it goes back inside
- if i>C TIR occurs
critical angle
greatest angle at which a ray can travel through and be refracted without TIR occurring
sinC = 1/n
uses of TIR
- transmit info quickly in high speed internet
- used in endoscopes in keyhole surgery
- along optical fibres + prisms + periscopes
