P6 - Waves Flashcards
What is a vaccum?
What is the speed of light in a vaccum?
An area with zero particles in it.
3x10^8
What happens to the refracted ray when it enters an optically denser block from air?
The refracted ray (light) bends (move) towards the normal.
What happens to a refracted ray when it goes from an optically denser block to air?
The refracted ray (light) will bend (move) away from the normal.
What happens to a wave during refraction?
- 4 points
- The wave speed will decrease
- The frequency will remain constant
- The wavelength will decrease
- Therefore the wave will change direction (and bend away from the normal).
What is the normal, when drawing a ray diagram?
The normal is a imaginary line (perpendicular - a straight line at 90 degrees) to the incoming ray where it hits the boundry
When the wave bends TOWARDS the normal, what happens to the speed of the wave?
When the wave bends towards the normal, the speed of the wave SLOWS down
When the wave bends AWAY from the normal, what happens to the speed of the wave?
When the wave bends AWAY from the normal, the speed of the wave will INCREASE
Describe Transverse waves
Give examples
Transverse waves oscillate perpendicular (at 90 degrees) to the direction of the energy transfer.
e.g Electromagnetic(light) waves, water waves
Describe Longitudinal waves
Give an example
Longitudinal waves oscillate parallel to the direction of the energy transfer.
e.g Sound waves
Define Wavelength
The distance from one point on a wave, to the same point on the next wave
Define Amplitude
The distance from the wave’s equilibrium to the crest/trough of the wave.
Define Frequency
The number of waves which pass a point per second.
Define Period
The time it takes one complete wave to pass a point.
Wave Speed Equation
Frequency x Wavelength
Period Equation
1 / frequency (Hz)
What is the method for measuring the speed of Sound waves in air?
- Distance two people a set distance apart; e.g 100m.
- Have the observer holding a stopwatch.
- Make a loud sound, e.g fire a Cannon.
- Have the observer start the stopwatch as soon as you fire the cannon, and stop the stopwatch as soon as the shot is heard.
- To measure the Speed of the Sound wave, you can do distance / time.
What can happen to light waves when the strike a boundry?
They can be; reflected, absorbed or transmitted - depending on the object they strike
What happens to reflected, absorbed and transmitted light waves when they strike a boundry?
Reflected light bounces off the objects surface.
Absorbed light heats the object.
Transmitted light passes through the object.
What is the frequency humans can hear?
20Hz to 20,000Hz
What are Ultrasounds waves and what can they be used for?
Ultrasond waves are sound waves with a higher frequency than humans can hear.
They can be used for detection and also medical imaging and also be used at a higher frequency to check castings.
What are seismic waves used for?
Earthquakes produce P and S waves. Describe the difference between P and S waves.
[2 marks]
Seismic waves are used for exploration.
P waves are fast longitudinal waves, which travel at different speeds through liquids and solids.
S waves are slow transervse, which cannot travel through liquids.
What is Echo sounding and what is it used for?
Echo sounding is a type of SONAR which uses high frequency sound waves to detect objects in deep water (e.g shipwrecks, shoals of fish) and measure water depth.
Describe how sound waves in the air are converted to vibrations in solids, by the ear.
[4 marks]
Compressions in the air cause the ear drum to flex inwards and outwards. This sets up vibrations of the bones in the inner ear.
