Waves

key terms, types

transverse wave

every point on the wave vibrates at 90 degrees to the direction of energy transfer

longitudinal wave

every point on the wave vibrates parallel to the direction of energy transfer

wavelength

distance from any point on a wave to where that exact point occurs again

frequency (Hz)

number of waves passing a point every second

time period

time taken to complete one full wave

time period equation

time period = 1/frequency

wave speed equation (m/s)

v = f x λ

how to answer calculations questions (vess)

values

equation

substitute

solve

infrasound

frequencies less than 20 Hz

ultrasound

frequencies more than 20000 Hz

speed equation

speed = distance / time

em spectrum

radiowaves

microwaves

infrared

visible light

ultraviolet

x rays

gamma rays

ionising waves

ultraviolet

x rays

gamma rays

uses of gamma rays

sterilising medical equipment

radiotherapy

uses of x rays

medical imaging

airport security

uses of ultraviolet

bank security

visible light

allows us to see

uses of infrared

short range communication

night vision

cooking

uses of microwaves

long range communication

cooking

refraction

when a wave goes from one medium to another and changes speed and direction

when a wave slows down

bends towards the normal

angle of i > angle of r

when a wave speeds up

bends away from the normal

angle of r > angle of i

lens

piece of glass used to refract light

types of lenses

convex and concave

convex lens rules

any ray travelling parallel to the principle axis gets refracted thought the focal point

any ray travelling through the centre of the lens does not get refracted at all

how to describe ray diagram image

inverted or upright

magnified, diminished or same size

real or virtual

total internal reflection

when a ray travels from a high dense medium to a low dense medium

critical angle

angle of incidence where the angle of refraction is 90

absorption

when the energy from the wave is transferred to the boundary

transmission

when the wave passes through the boundary

object staying at constant temperature

rate of energy being absorbed is equal to the rate of energy being emitted

object getting hotter

rate of energy being absorbed is greater than the rate of energy being emitted

object getting colder

rate of energy being emitted is greater than rate of energy being absorbed

s waves

transverse

p waves

longitudinal

s waves travel

through solids but not liquids

p waves travel

through solids and liquids