waves Flashcards
Define wavelength.
The distance between the same points on two consecutive waves.
Define amplitude.
The distance from the equilibrium line to the maximum displacement (crest or trough).
Define frequency.
The number of waves that pass a single point per second.
Define a period.
The time taken for a whole wave to completely pass a single point.
What is the equation for velocity?
Frequency x wavelength.
What is the equation for a period?
1
——————
Frequency
Increased frequency =
Increased velocity.
Increased wavelength =
Increased velocity.
A period is inversely proportional to…
Frequency.
A smaller period =
Higher frequency and greater velocity.
What are 2 examples of transverse waves?
~Light waves
~Electromagnetic waves
Do transverse waves have peaks and troughs or compressions and rarefactions?
Peaks and troughs.
In transverse waves, vibrations are…
At right angles to the direction of travel.
What is an example of a longitudinal wave?
Sound waves.
Do longitudinal waves have peaks and troughs or compressions and rarefactions?
Compressions and rarefactions.
In longitudinal waves, vibrations are…
In the same direction as the direction of travel.
What must a surface be for waves to reflect off of it?
Flat.
The smoother the surface…
The stronger the reflected wave.
Why do rough surfaces appear matte and not reflective?
As they scatter light in all directions.
Angle of incidence =
Angle of reflection.
Electrons absorb the light energy, then…
Re-emit it as a reflected wave.
The more transparent a material is…
The more light will pass through it.
If the frequency of the light matches the electron’s energy levels…
Light will be absorbed by the electrons and won’t be re-emitted.
If a material appears green…
Only green light has been reflected and the rest of the frequencies in visible light have been absorbed.
What do sound waves cause when they travel through solids?
Vibrations.
Compression forces the eardrum…
Inward.
Rarefactions forces the eardrum…
Outward due to pressure.
What do small bones in the ear do?
Amplify sound waves.
The eardrum and small bones vibrate at…
The same frequency as the sound wave.
What happens when hairs attuned to the specific frequency move a lot?
An electrical impulse is released to the brain where the brain interprets this to a sound.
What is the normal human hearing range?
20Hz - 20kHz.
Hairs attuned to higher frequencies in the cochlea can die or be damaged by…
~Constant loud noise
~Changes in the inner ear
~Smoking, chemotherapy and diabetes
Which type of sound can humans not hear?
Ultrasound.
What is the opposite of ultrasound?
Infrasound. (seismic waves)
What is a seismic wave?
A sound wave with a frequency that is less than 20Hz.
What is a P wave?
A longitudinal wave which can pass through solids and liquids.
What is an S wave?
A transverse wave that moves slow and can only pass through solids.
What do electromagnetic waves not need to move?
Particles.
In space all electromagnetic waves have…
The same velocity.
Electromagnetic waves can transfer…
Energy from a source to an absorber.
What is an example of an energy transfer from a source to an absorber?
A microwave to food.
In electromagnetic waves, as wavelength decreases…
Frequency must increase.
In electromagnetic waves, as frequency increases…
The energy of the wave increases.
If entering a denser material, refraction…
Bends towards the normal.
If entering a less dense material, refraction…
Bends away from the normal.
Substances will absorb, transmit, refract or reflect certain EM waves depending on…
Wavelength.
What are radio waves produced by?
Oscillations in electrical circuits.
When radio waves are absorbed, they create…
An alternating current at the same frequency.
Why are radio waves used for TV?
As they have a long wavelength and can travel far without losing quality.
Why are microwaves used for satellite communication?
As they can penetrate the atmosphere.
Why are infrared waves used for cooking food?
As they transfer thermal energy.
Why are visible rays used for fibre optics?
As they have the best reflection / scattering in glass.
Why are UV rays used in tanning and energy efficient lamps?
They radiate the least amount of heat but more energy.
Why are X-ray waves used in medical imaging and treatment?
As they are very high in energy and can penetrate material easily.
Concave lenses are thinner…
At the centre.
Convex lenses are wider…
At the centre.
Concave lenses spread…
Light outwards.
Convex lenses focus…
Light inwards.
In concave lenses, light appears to have come from…
The focal point.
In convex lenses, horizontal rays focus…
Onto the focal point.
