Electromagnetic waves Flashcards
properties of all electromagnetic waves: (3)
- transverse
- travel at the same speed through a vacuum (3x10^8)
- transfer energy as radiation from the source of the waves to an absorber
what is the correlation between frequency, wavelength and energy between the waves of the electromagnetic spectrum? (2)
- waves with a very short wavelength, high frequency and high energy
- waves with a very long wavelength, low frequency and low energy
name the electromagnetic waves and state their properties (generalised):
Radio waves, Microwaves, Infrared, Visible light, Ultra violet, X-ray, Gamma
long wave length short wavelength
low frequency ——————————————————————-> high frequency
low energy high energy
which colours from the visible light spectrum have the highest and lowest frequency: (2)
- red light has the lowest frequencies of visible light
- violet light has the highest frequencies of visible light
what does the behaviour of an electromagnetic wave depend on?
its frquency
what does the increase of frequency mean for the electromagnetic waves?
EM waves become progressively more hazardous.
how are radio waves transmitted?
why are they safe?
- through air
- they do not cause damage if absorbed by the human body
how can radio waves be produced?
by oscillations in electrical circuits.
describe the process of producing radio waves: (4)
- radio waves are absorbed by a conductor,
- they create an alternating current.
- this electrical current has the same frequency as the radio waves.
- information is coded into the wave before transmission, which can then be decoded when the wave is received.
describe some usages of radio waves: (3)
- broadcasting
- communications
- satellite transmissions
describe some usages of microwaves: (3)
- cooking
- communications
- satellite transmissions
describe how microwaves work: (2)
- high frequency microwaves have frequencies which are easily absorbed by molecules in food.
- internal energy of the molecules increases when they absorb microwaves, which causes heating.
why are microwaves appropriate for satellite communication? (2)
- pass easily through the atmosphere
- so they can pass between stations on Earth and satellites in orbit.
describe the DANGERS of microwaves:
internal heating of body cells
describe some usages of infrared waves: (6)
cooking, thermal imaging, short range communications, optical fibres, television remote controls security systems
describe the DANGERS of infrared:
causes skin burns
why is infrared appropriate for usage in electrical heaters and for cooking food? (3)
- it has frequencies which are absorbed by some chemical bonds.
- internal energy of the bonds increases when they absorb infrared light
- which causes heating. This makes infrared light useful for electrical heaters and for cooking food.
why is infrared useful for detecting people in the dark? (3)
- all objects emit infrared light.
- human eye cannot see this light, but infrared cameras can detect it.
- this is ‘thermal imaging’
describe some uses of visible light: (3)
vision, photography and illumination
describe some uses of ultraviolet: (3)
fluorescent lamps,
detecting forged bank notes
disinfecting water
describe the DANGERS of ultraviolet:
damage to surface cells and eyes, leading to skin cancer and eye conditions
describe some usages of x-rays: (3)
observing the internal structure of objects,
airport security scanners
medical x-rays
describe some usages of gamma rays: (2)
sterilising food and medical equipment,
detection of cancer and its treatment
describe the DANGERS of x-rays and gamma rays:
both are ionising, which can cause the mutation of genes, leading to cancer
what do all bodies do?
-irrespective of what?
- emit and absorb infrared radiation.
- their temperature
what is the temperature of a body linked to?
balance between the amount of radiation absorbed and emitted
describe the correlate between the rate of absorption and the temperature of a body: (3)
if greater than rate of emission = increasing body temperature
if equal to rate of emission = constant body temperature
if lower than rate of emission - decreasing body temperature
