topic 6 continued Flashcards
how do EM waves transfer energy
they transfer energy from the source of the waves to an absorber
how do microwaves transfer energy
from the source which is the microwave to the absorber which is the food
the frequency … from radio waves to the gamma rays
increases
the wavelength … from radio waves to the gamma rays
decreases
what can EM waves travel through
a vacuum (space)
all EM waves travel at the same … in a vacuum
speed
at what speed do EM waves travel in a vacuum
3 x 10^ 8 m/s
what happens when EM waves are generated or absorbed
changes takes place in atoms or in the nuclei of atoms
how can an em wave be generated
by a change to the nucleus
how can radio waves be produced
when electrons oscillate (move backwards and towards)in electric circuits
give an example of how radio waves can be absorbed
by an electrical circuit in an aerial- this causes the electrons in the circuit to oscillate
what type of current can radio waves create and what does it have the same of
alternating current with the same frequency as the radio waves
why are radio waves used in TVs and radios
because they can travel long distances before being absorbed e.g. by buildings and trees
what can radio waves do in the atmosphere
they can reflect off a layer of charged particles in the atmosphere- this allows us to send radio waves at very long distances around the earth
why are microwaves used in communication with satellites
because microwaves can pass through the earths atmosphere without being reflected or refracted
why is infra-red used to heat objects etc
because the energy of the infra-red is easily absorbed by the surface of the objects
What can EM waves do that leads to refraction
They travel at different speeds in different materials
EM waves vary in wavelength from …
10^-5 - 10^4
Wavelength of radiowaves
1m - 10^4
Microwaves wavelength
10^-2m
Infra-red wavelength
10^-
Visible light wavelength
10^-7m
Ultraviolet wavelength
10^-*8m
X-rays wavelength
10-10 m
