Waves Flashcards
what is amplitude?
the greatest displacement of a wave, measured from the midpoint
what is the wavelength?
the length of one oscillation (cycle) of a wave - the distance from a point on one qave to the equivalent point on the adjacent wave
what is frequency?
the number of oscillations (cycles) of a wave per second, measured in Hertz (1 Hz is one oscillation per second)
what is the time period?
time for one oscillation (cycle) of a wave
how do you calculate period?
1 / frequency
how do you calculate wave speed?
frequency x wavelength
what is the rest position?
the undisturbed position of particles or fields when they are not vibrating
what is displacement?
the distance that a certain point in the medium has moved from its rest position
what is a peak?
the highest point above the rest position
what is a trough?
the lowest point below the rest position
do electromagnetic waves need a medium to travel through?
no
do mechanical waves need a medium to travel through ?
yes
are frequency and wavelength directly or inversely proportional ?
inversely
do transverse waves oscillate perpendicular or parallel to the direction of energy transfer?
perpendicular
longitudinal waves oscillate perpendicular or parallel to the direction of energy transfer?
parallel
what are some examples of transverse waves?
- light
- all EM waves
- ripples on water
- S waves (seismic)
what are some examples of longitudinal waves?
- sound
- ultrasound
- pressure waves
- P waves (seismic)
what is a compression?
Region in a longitudinal wave where the particles are closest together.
what is a rarefaction?
regions in a longitudinal wave of low pressure due to particles being spread further apart
angle of incidence = ?
angle of reflection
what happens when light passes through an object?
some of the light is reflected, some of the light is transmitted, and a small amount may be absorbed
what is specular reflection?
reflection from a smooth surface which gives a sharp image
what is diffuse reflection?
reflection from a rough surface - light is scattered in lots of different directions
what happens as light passes from air into glass?
it moves towards the normal (AOI is greater than AOR)
what happens as as light passes from glass into air?
it moves away from the normal (AOI is less than AOR)
why does light refract?
due to a change in speed when it enters an optically denser material
what is the speed of sound in air?
330 m/s
why does sound travel faster in solids and liquids?
because it will be transmitted through the material faster as the particles are much closer together
how do ears detect sound?
- Sound waves enter the ear canal and cause the eardrum to vibrate.
- Three small bones transmit these vibrations to the cochlea.
- This produces electrical signals which pass through the auditory nerve to the brain, where they are interpreted as sound.
what is the human hearing range?
20Hz to 20000 Hz
what is ultrasound?
sound waves with a frequency over 20kHz or 20,000 Hz
why is ultrasound useful?
it is not ionising or heating
what is ultrasound used for?
- medical scans
- cleaning medical equipment and jewellery
- finding flaws in metal
how can ultrasound be used to detect flaws?
- when ultrasound reaches a boundary between two substances with different densities, they are partly reflected back and the remainder of the waves pass through
- detector placed near source of waves detects the reflected waves
- detector measures the time between a wave leaving the source and reaching the detector - the further the boundary, the longer the time between leaving the source and reaching the detector
- if wave takes less time than usual to reflect back, something must have been in the way to reflect this wave - therefore there is a flaw there
describe the structure of the earth
- solid inner core
- liquid outer core
- solid mantle
- solid crust
what are the 2 types of seismic waves?
- primary waves (P waves)
- transverse waves (S waves)