4) Waves Flashcards
What do transverse waves cause particles in the medium to do?
Vibrate at right angles to the direction of the wave’s motion
What are real world examples of transverse waves?
Corks bobbing
Mexican wave
What do waves transfer?
Energy
What do longitudinal waves cause particles in the medium to do?
Vibrate in the same direction as the wave’s motion
What are examples of longitudinal waves?
P-waves
Sound waves
What do all waves have?
A frequency
A period of oscillation
What is a wave’s frequency?
Number of oscillations per second
What is an oscillation?
A vibration
What is frequency measured in?
Hertz (Hz)
What are the equations for frequency?
frequency = number of oscillations / time frequency = 1 / period
What is a period of a wave?
The time taken to complete one oscillation
What is equation for a wave’s period?
period = 1 / frequency
What is the period of a wave measured in?
Seconds (s)
What is the amplitude of wave?
The greatest distance a point on a wave moves from its rest position
What is the wavelength?
The distance between two peaks of adjacent waves
What are wavefronts?
Parallel lines at the peaks of ripples
What is the equation for wave speed?
wave speed = frequency x wavelength
What is the best way to observe water waves?
A ripple tank
What happens when a wave travels from one medium to another?
Speed changes
Wavelength changes
Frequency stays the same
What part of waves are directly proportional?
Speed and wavelength
Why is the frequency of a wave unchanged between mediums?
The source is still producing the same number of osciallations per seconds
When does reflection happen?
Wave hits a flat surface (plane) and bounces off
What can happen to waves at the boudnary of a medium?
Refraction
Reflection
Absorbtion
Transmission
Why does refraction happen?
If the wave crosses the medium at an angle the change in speed will cause the direction to change
What is absorbtion?
When energy is absorbed by the material
What is transmission?
When waves catry on travelling through a new material
What does transmission often lead to?
Refraction
What is the angle of incidence?
The angle between the incident ray and the normal
What is the incident ray?
The incoming light ray to a medium
What is the normal line?
A line at 90 degrees to the plane
What is the angle of reflection?
The angle between the reflected ray and the normal
What does the law of reflection state?
The angle of incidence = the angle of reflection
What is the flat surface light rays hit called?
The plane
What happens to light when it enters a more optically dense medium?
It slows down
What happens to light when it enters a less optically dense medium?
It speeds up
How does light refract when entering a more optically dense medium?
It is refracted closer to the normal
Angle of refraction is smaller than angle of incidence
How does light refract when entering a less optically dense medium?
It is refracted further from the normal
Angle of refraction is larger than angle of incidence
What type of waves are sound?
Longitudinal waves
How is sound produced?
By the vibration of particles in a medium
What is a medium?
The subtance that waves travel through
What do waves travel in a series of?
Compressions and rarefractions
What are sound compressions?
Where the medium is squashed together?
What are sound rarefractions?
Where the medium is stretched apart
What sound range can we hear?
20Hz - 20,000 Hz
What is ultrasound?
Sound waves above 20,000 Hz
What is infrasound?
Sound waves below 20 Hz
What are seismic waves?
Infrasound
What do doctors use ultrasound for?
Scanning a developing foetus
How does a rigid medium affect the speed of sound?
More rigid = higher speed
How does a compressible medium affect the speed of sound?
More compressible = lower speed
How quick is sound in gases?
Very slow as gas is easily compressable
How quick is sound in solids?
Quicker than liquids or gases as more rigid
How quick is sound in gases?
Quicker than gas as more rigid
Why can sound waves not travel in space?
It is a vacuum
No medium for sound waves to travel through
No particles to vibrate
What are the stages of sound in the ear?
1) Sound waves make ear drum vibrate
2) Passed via small bones (anvil, hammer, stirrup)
3) Auditory nerve
4) Sends an electrical signal to brain
What can we use ultrasound waves for?
Medical imaging
Industrial imaging
How is ultrasound used in medicine?
1) Ultrasound waves pass through body
2) When reaching a boundary between two different materials, some will be reflected which we can detect
3) A computer processes the timing and distribution of these waves and develops a video image
How is ultrasound used in industry?
Can find flaws in materials
Usuallly ultrasound is reflcted by the far side of a material
Flaws reflect waves sooner telling us there is a problem
How is ultrasound useds to find water depth?
Echo sounding
1) Send ultrasound pulse into water
2) When pulse hits surface it is reflected back
3) We can work out distance travelled by recording time taken
What 2 types of seismic wave do earthquakes produce?
P-waves (primary)
S-waves (secondary)
What type of wave are P-waves?
Longitudinal seismic waves
What type of wave are S-waves?
Transverse, seismic waves
What can S-waves travel through?
Solids
What can P-waves travel through?
Solids
Liquids
What happens if the incident ray is at the critical angle?
The refracted light travels parallel to the boundary of two mediums
