Waves Flashcards
What is a transverse wave?
Oscillations are perpendicular to the direction of travel
What is a longitudinal wave?
Oscillations are parallel to the direction of travel
What is amplitude?
Maximum displacement from the normal position
What is frequency?
Number of waves per second
What is wavelength?
Distance from crest to next crest
What is Time Period?
Time for wave to complete one oscillation
Equation: Wave speed v =
v = frequency x wavelength
Equation: Frequency f =
f = 1/time period f = 1/T
Give an example of a longitudinal wave.
Sound
Give an example of a transverse wave.
Electromagnetic spectrum
Water waves
What is the Doppler effect?
When the source of a wave moves towards the observer, observed frequency increases.
When a source moves away, observed frequency decreases.
What do all waves do?
Transfer energy and information without transferring matter.
List the electromagnetic spectrum in order of decreasing wavelength and increasing frequency.
Radio Microwaves Infra Red Visible Light (ROYGBIV) Ultra violet X Rays Gamma rays
Give a use and hazard of gamma rays?
use: sterilising food and medical equipment
hazard: cancer and cell mutations
Give a use and hazard of X rays?
use: observing internal structures like bones
hazards: cancer and cell mutations
Give a use and hazard of ultra violet.
use: fluorescent lamps, tanning lamps, checking counterfeit money
hazards: damage tovsurface cells of the skin and blindness
Give a use and hazard of infra red.
use: heaters and night vision
hazards: skin burns
Give a use and hazard of microwaves.
use: cooking and satellite communications/moblie phones
hazards: internal heating of body tissues
Give a use of visible light.
photography
Give a use of radio waves.
broadcasting and communications
radar
What properties do all electromagnetic waves have in common?
all transverse waves
all travel in a vacuum
all travel at same speed in a vacuum (300 000 000m/s)
What is the Law of reflection?
Angle of incidence = angle of reflection
What must you remember when measuring the angles of incidence and reflection?
measured between the ray and the normal
Equation for refective index n =
n = sin i/ sin r
What are the 2 conditions for Total internal reflection to occur?
- Ray travelling from a higher refractive index to a lower refractive index
- at an angle greater than the critical angle
What is the critical angle?
Angle at which the ray refracts at 90 degrees along the boundary. Angle greater than critical and total internal reflection occurs.
For critical angle c sin c =
sin c = 1 / n
Refraction is the change of direction of a wave what changing speed.
Travelling from less optically dense to more optically dense medium, what happens to speed, wavelength and frequency?
less dense to more dense:
speed decreases
wavelength decreases
frequency stays the same
Refraction is the change of direction of a wave what changing speed.
Travelling from more optically dense to less optically dense medium, what happens to speed, wavelength and frequency?
more dense to less dense:
speed increases
wavelength increases
frequency stays the same
What is the frequency for human hearing?
20 to 20 000 Hz
Pitch of sound is related to ….
frequency
Loudness of sound is related to ….
amplitude
What equipment do we use to investigate sound waves?
mircrophone connected to an oscilloscope
What equipment do we need to investigate speed of sound?
Two microphones 2 m apart Make sound with hammer First microphone starts timer Second timer stops microphone Repeat and find an average Speed = distance / time
What is a wavefront?
Line of points in phase with each other (move together)
Waves transfer energy and information without ….
transferring matter.
Is light longitudinal or transverse?
transverse
Is sound longitudinal or transverse?
longitudinal
Name two uses of total internal reflection
fibre optics in cable tv and endoscopes
prism binoculars
All waves can be …..
All waves can be reflected and refracted
