Waves Flashcards
What are waves?
Transfer energy from one place to another without transferring matter
Longitudinal or transverse
What happens in water and air?
It is the wave not the substance that moves
An object dropped on water causes ripples but neither the object nor water moves with the ripples
When you speak, the voice box vibrates, making sound waves travel through air. The air itself does not travel away from your throat
What do mechanical waves need?
A medium to travel through, causing the particles in the substance to oscillate and pass energy on to neighbouring partciles
What are transverse waves?
The oscillations of a transverse wave are perpendicular to the direction in which the waves transfer energy
E.g ripples on the surface of the water
What are longitudinal waves?
The oscillations are parallel to the wave direction
Cause areas of rarefaction and compression
E.g sound waves
Amplitude
Maximum displacement of a point on a wave from its undisturbed position (m)
Frequency
Number of waves passing a fixed point per second
Period
Time taken for one complete wave to pass a fixed point
Wavelength
Distance from one point on a wave to the equivalent point on the next wave
Wave speed
Distance travelled by each wave per second and the speed at which energy is transferred by the wave (m/s)
How do you calculate period?
1/ frequency
What happens when waves travel from one medium to another?
Speed and wavelength may change but frequency stays the same
What is speed?
Distance/ time
What happens when a wave arrives at the boundary between two diffrent substances?
Absorption
Reflection
Refraction
Transmission
Absorption
The energy of waves is transferred to the energy stores of the substance they travel in
Reflection
The wave bounces back
Refraction
The wave changes direction and speed as it crosses the boundary
Transmission
The waves carry on moving once they cross the boundary but may be refracted
What are ray diagrams?
Show what happens when a wave is reflected at a surface
Use a ruler
Draw a single arrow on the rays and a dotted line for the normal at a right angle to the point of incidence
Label the normal, angle of incidence and angel of reflection
Angle of incidence = angle of reflection
The shorter the wavelength…
The higher the frequency
Longitudinal wave examples
Sound
Seismic P waves
Transverse waves examples
Ripples on a pond
Waves on a string
Seismic S waves
Electromagnetic waves
What do longitudinal waves do?
Stretch and compress
What do transverse waves do?
Up and down
P wave
Faster
Travels through liquid
Reflected or refracted
Fasted in inner core
Higher density faster
S wave
Fastest in lower density
Transverse
Slower
Cannot travel through liquids
5km/s
Reflected or refracted
