Waves & Radiation: Waves Flashcards
Define a ‘transverse’ wave, and provide examples.
A ‘transverse’ wave is a wave in which the medium vibrates at right angles to the direction of its propagation.
Some examples of transverse waves are water, and any member of the EM spectrum.
Define a ‘longitudinal’ wave, and provide examples.
A ‘longitudinal’ wave is a wave vibrating in the direction of propagation.
An example of a longitudinal wave is sound.
Describe these basic wave properties: Crest, Trough, Wavelength, Amplitude.
The crest is the highest point on a wave.
The trough is the lowest point on a wave.
The wavelength is the distance until a wave repeats itself.
The amplitude is the height of the wave from the rest position.
What is the ‘wave equation’, which links wavelength, frequency, and speed?
The wave equation is ‘v = fλ’
(velocity = frequency * wavelength)
What is the frequency of a wave, and what is the equation we can use to find it?
The frequency of a wave is the number of waves produced in one second.
This is the same as the number of waves that pass a point in one second.
It is measured in hertz (Hz).
The ‘frequency’ equation is F=N/t
(Frequency = number of waves passing a point / time)
What is the period, and what formula can we use to calculate it?
The period is the time it takes for one complete wave to pass a point.
The ‘Period’ formula is T = 1/f
(Period = 1 / frequency)
What medium can light not travel through?
Light cannot travel through a vacuum.
Describe an experiment which measures the speed of sound in air.
Two microphones are placed at a set distance away from each other, this distance is measured (d).
A sound is made which travels through both microphones. The time it takes between the sound being picked up by each microphone is your time (t).
The formula (v = d/t) is used, linking the distance and time we have measured providing us the speed.
What is the speed of sound in air, roughly?
The speed of sound in air is roughly (by SQA standards) 340ms-1.
What is the speed of light in air, roughly?
The speed of light in air is roughly (by SQA standards) 3x108ms-1.
Provide an example proving that the speed of light is faster than the speed of sound.
An example which can prove that the speed of light is faster than the speed of sound is lightning and thunder.
In a thunder storm, you will always see the lightning before the thunder.
This is because the storm could be kilometres away, yet the speed of sound can only travel a kilometre in about 3 seconds, whereas light will arrive near instantly.
State the members of the Electromagnetic Spectrum in order of increasing wavelength.
Gamma, X-rays, Ultraviolet, visible light, infrared, microwaves, radio waves.
What can be said about the speed of all Electromagnetic Waves?
All Electromagnetic Waves travel at the speed of light (3x108ms-1).
State a suitable use for ‘Infrared Radiation’.
A use for ‘Infrared Radiation’ would be IR cameras on police helicopters.
Infrared cameras take in the heat (infrared) that is emitted from an object, and provide a certain colour based on the specific heat.
Humans have a fairly high body temperature, and therefore can be picked up by these cameras quite easily.
State 2 suitable uses for ‘Ultraviolet Radiation’, and briefly describe its source & risks.
A use for ‘Ultraviolet Radiation’ would be sun beds and security pens.
Ultraviolet is found naturally in sunlight, and it causes tanning and burning of skin.
Overexposure to Ultraviolet Radiation can lead to skin cancer.
‘Sun beds’ allow for cosmetic tanning of the skin.
‘Security pens’ check for forged banknotes in banks & other areas.