P13 Electromagnetic Spectrum Flashcards
what part of the electromagnetic spectrum can humans detect?
visible light
what is the speed of all electromagnetic waves?
3 x 10^8 m/s
what is meant by a ‘continuous spectrum’?
the cut off point between each type of wave is not always clear
what are the waves in the electromagnetic spectrum?
gamma
x-ray
ultraviolet
visible
infrared
microwaves
radio
how do the properties differ from the gamma end of the spectrum to the radio end of the spectrum?
gamma - high frequency with short wavelength
radio - low frequency with long wavelength
what are electromagnetic waves?
transverse waves that transfer energy from a source to an absorber
what are the properties of waves at the violet end of the visible light spectrum?
higher frequency with a shorter wavelength
what are the properties of waves at the red end of the visible light spectrum?
lower frequency with a longer wavelength
what happens when EM waves are generated or absorbed?
changes take place in the atom or nuclei of the atom
how can EM waves be generated?
electrons move energy levels
changes take place in the nucleus
what can EM waves be emitted and absorbed over?
they can be emitted or transmitted over a large range of frequencies
what are the hazards of UV, X rays and gamma rays?
UV - increase the risk of skin cancer, age skin prematurely
gamma + x rays - ionising radiation. this can cause mutation of genes which increases risk of skin cancer
how can radio waves be produced?
when electrons oscillate in electronic circuits
how can radio waves transmit information?
radio waves can be transmitted to have the same frequency as an electrical circuit.
they can then be transmitted and then absorbed by an aerial and create an alternating current with the same frequency of the wave
what are radio waves used for and why?
to transmit radio and terrestrial TV (TV received using an aerial) signals
they are used because they can travel long distances before being absorbed
they can also spread out between hills (diffraction)
they can also reflect off the ionoshpere so radio waves can travel long distances around the earth
what are microwaves used for and why?
to heat food - water molecules absorb the microwaves’ energy
communicate with satellites in space - microwaves can travel through the atmosphere unaffected
what can infrared be used for and why?
emitted by electrical heaters and heats food - infrared is easily absorbed by the surface of objects
infrared cameras
what is visible light used for and why?
communications (fibre optic cables) - pulses of light are sent down optical fibres to transmit information. visible light has a short wavelength so can carry lots of information
what is ultraviolet used for and why?
energy efficient light bulbs - UV has a shorter wavelength so can carry more energy than visible light. the energy of the UV is then absorbed by the surface of the bulb and converted to visible light. this requires less energy than using visible light
tanning beds - can cause premature ageing and increase risk of skin cancer
what can X rays and gamma rays be used for and why?
medical imaging - very penetrative and X rays are absorbed by bones so we can see them in the scans
medical treatments
what do all objects do with infrared radiation?
all objects, no matter what temperature, emit and absorb infrared radiation
what does the wavelength and intensity of the radiation depend on?
the temperature of the object
what is the wavelength of very hot objects?
they emit shorter wavelength radiation than cooler objects
what is a perfect black body?
an object which absorbs all of the radiation incident on it
no radiation is reflected or transmitted
what is the best possible emitter of radiation?
a perfect black body
what happens if an object is warmer than the surroundings?
it will emit more radiation than it absorbs and the temperature of it will decrease
what happens if an object is cooler than its surroundings?
it will absorb more radiation than it emits so its temperature will increase
what is happening if an object is at a constant temperature?
it is absorbing radiation at the same rate as it is emitting it
what happens to the infrared radiation from the Sun?
some is reflected back into space
the rest is absorbed by the Earth. the Earth then emits the radiation back into space. some of this radiation is re-radiated by greenhouse gases in the atmosphere
what is happening due to human activity?
the levels of greenhouse gases is increasing which means more infrared radiation is being trapped
