Waves Flashcards
What is ‘rarefaction’?
An area of reduced pressure.
What is a longitudinal wave?
Waves where the oscillations are parallel to the direction of wave travel.
Give an example of a longitudinal wave.
E.g: sound waves, seismic P-waves, ultrasound waves
What is a way to remember longitudinal waves?
‘P’ sound: longitudinal waves (like seismic P-waves) - thought of as pressure or push waves - particles move parallel to the wave.
What are the movements of a longitudinal wave like?
Pushing and pulling a stretched slinky.
What is a transverse wave?
A wave where the oscillations are perpendicular to the direction of wave travel.
What is an example of a transverse wave?
E.g: a Mexican wave, electromagnetic waves (like light waves, microwaves, radio waves)
What are the movements of a transverse wave like?
Moving a rope up and down.
What is amplitude?
The maximum displacement of a point fixed on a wave from its undisturbed position.
What is frequency?
The number of waves passing a fixed point per second.
What is period?
The time taken for one complete wave to pass a fixed point.
What is wavelength?
The distance from one point on a wave to the same point on the next wave.
What is wave speed?
Distance travelled by each wave per second, and the speed energy is transferred by the wave.
What equation relates period and frequency?
Period = 1 ÷ frequency
What quantity always stays the same?
Frequency
What is absorption?
When the energy of a wave is transferred to the energy stores of the substance it travels into.
What is reflection?
When the waves bounce back.
What is refraction?
When the waves change speed and direction as they cross the boundary.
What is transmission?
When the waves carry on moving once the boundary has been crossed.
They may still be refracted.
What is an EM wave?
Transverse waves that transfer energy from their source to an absorber.
What is the speed of all EM waves in a vacuum?
3 x 10^8 m/s
When does refraction occur in EM waves?
When there is a change in the wave’s velocity.
How do sound waves cause us to hear?
Sound waves cause particle vibrations which ultimately cause the vibration of our ear drums (and other parts)
Why are ultrasound waves used for medical and industrial imaging?
- Ultrasound waves are partially reflected when they meet a boundary between two different media.
- The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is.
What is a way to remember the EM spectrum?
Raging Martians Invade Venus Using X-ray Guns
Radio Micro Infrared Visible light UV X-ray Gamma
What sort of radiation is emitted by all (hot) objects?
Infrared
What colour is the best absorber and emitter of infrared radiation?
Matte black
What colour is the worst absorber and emitter of infrared radiation?
Shiny silver
Describe the method for the Leslie cube infrared experiment.
- Fill cube (has black and shiny silver surface) with hot water.
- Use infrared detector at various points (at same distance from surface).
- Record temp.
- Repeat and calculate mean.
- Determine which surface is better emitter/absorber.
Name a use of radio waves.
Television, radio signals
Name a use of micro waves.
Satellite communication, cooking food
Name a use of infrared waves.
Cooking food, infrared cameras, electrical heaters
Name a use of visible light waves.
Fibre optic communication
Name a use of ultraviolet waves.
Tanning, energy-efficient lights
Name a use of X-rays or gamma rays.
Medical imaging and treatments
What is a hazard of UV radiation?
Damage skin cells, premature aging of skin, skin cancer, blindness
What is a hazard of Gamma and X-rays?
Damage cells, mutation of genes leading to cancer
Why are waves further down the EM spectrum more dangerous?
They are more ionising so can damage cells
What type of EM wave has the shortest wavelength?
Gamma
What type of EM wave has the longest wavelength?
Radio
What type of EM wave has the highest frequency?
Gamma
What type of EM wave has the lowest frequency?
Radio
What does a wave bend towards when it is refracted?
The normal
What type of wave is sound?
Longitudinal
Where is amplitude measured from?
Middle to peak of wave
Where is wavelength measured from?
A point (usually peak) on one wave to identical point on next wave
What type of waves are light waves?
Transverse
What type of waves are all EM waves?
Transverse
How can seismic waves be used to explain the structure of the Earth?
P-waves can travel through liquids and solids
S-waves can only travel through solids
The fact that P-waves can travel through the Earth tells us that some of the structure of Earth is liquid.
What are ultrasound waves?
Waves with a frequency above 20kHz.
What colours are part of the visible light spectrum?
Red, orange, yellow, green, blue, indigo, violet
