Waves Flashcards
What are transverse waves?
Where the oscillations are perpendicular to the direction of travel.
What are longitudinal waves?
Where the oscillations are perpendicular to the direction of travel.
What is the period of a wave?
The time taken for one wave to pass a given point.
What are the sections of the electromagnetic spectrum?
Radio waves, microwaves, infra-red, visible light, UV, X-rays and gamma rays.
What are the speed of electromagnetic waves?
300,000,000m/s in air.
What are the wavelength of electromagnetic waves?
From kilometers to 10⁻¹²m.
What are the frequencies of electromagnetic waves?
From 10²Hz to 10²⁰Hz.
What are the properties of electromagnetic waves?
They all travel at 3×10⁸m/s. They can all be transmitted, absorbed, reflected and refracted.
Why does a light ray change direction during refraction?
Due to the change in wave speed.
How do electromagnetic waves affect a circuit?
They may introduce an alternating current.
What happens when waves travel into denser materials?
They slow down, their wavelength decreases and they refract towards the normal.
What happens to waves travelling into a less dense material?
They speed up, their wavelength increases and they refract away from the normal.
How fast is the speed of sound?
330m/s.
How are atoms affected when they absorb electromagnetic radiation?
Electrons jump up an energy level.
Which three wave types can harm human body tissues?
UV, X-rays and gamma rays.
Why do some electromagnetic waves cause damage to human tissue?
The higher the frequency of electromagnetic waves, the more ionising it is.
How does UV cause tissue damage?
Premature skin aging and an increased risk of skin cancer.
How do X-rays and gamma rays cause tissue damage?
Ionising radiation can cause mutations of genes, causing cancer.
How are radio waves used?
In television and radio, produced by oscillations in electrical circuits; able to be sent long distances by reflecting off charged layer in atmosphere, detected by aerials; cause alternating current to flow with the same frequency as the signal.
How are microwaves used?
For satellite communications, cooking; able to pierce atmosphere, absorbed by food molecules so the wave energy is transferred into kinetic energy of particles and food’s temperature increases.
How are infrared waved used?
With electrical heaters, cooking food, cameras, transferring energy as heat, not detectable by our eyes, used to see warm objects in dark places.
How are visible waves used?
Through fibre optic communications, light pulses can totally internally reflect along the insides of fibre optic cable, taking a digital signal over a long distance.
How are UV waves used?
For energy efficient lamps, sun tanning, UV is absorbed by coating on lamps and re-emitted as visible, UV causes pigment melanin in the skin to turn darker.
How are X-rays and gamma rays used?
For medical imaging and treatments, both are penetrative and are partially absorbed by body tissues and can be used for imaging or using ionising radiation to kill unwanted cells.
