EM Spectrum Video Lecture | Physics Class 12 - NEET

the electromagnetic spectrum light is
actually an electromagnetic wave and is
part of a whole spectrum of waves called
the electromagnetic spectrum the waves
all have certain things in common they
all travel at the speed of light in a
vacuum and they can all be reflected
refracted and diffracted so how are the
different parts different well it's the
frequency and the wavelength that change
so here on the screen is the
electromagnetic spectrum we have radio
waves on the Left they have the longest
wavelength and the lowest frequency and
as we move from left to right the
wavelength decreases and the frequency
increases also the energy the wave
carries increases as well now next to
radio waves is microwaves then we have
infrared followed by visible light which
is in right bang in the middle of the
spectrum then we have the high energy
side with ultraviolet x-rays and finally
gamma rays you need to memorize this
spectrum and know how the wavelength and
frequency change as you move along it ok
let's look some more at the lower energy
half of the spectrum from radio waves up
to visible light all these parts of the
spectrum are used in communications
radio waves are used for sending TV and
radio signals both short and long
distances really short wavelengths are
used for very short distances and the
longer wavelength for longer distances
as they can reflect off a layer of
charged particles in the atmosphere
called ionosphere
however radio waves can't pass through
the ionosphere so if we want to
communicate with satellites we must use
microwaves as they will easily pass
through the ionosphere microwaves are
also used in mobile phones and certain
wavelengths are absorbed strongly by
water molecules and so used to cook food
these are not the wavelengths however
that are used in mobile phones infrared
as we know carries heat and can be used
in thermal imaging and for grills for
cooking
and it is also used in communications as
is visible light both being sent down
optical fibers so all these for lower
energy electromagnetic waves are used in
communication but is there any danger in
using them well at the moment there is
no scientific evidence that any of these
parts of the EM spectrum pose any danger
whatsoever apart from maybe getting
burnt by infrared now let's move on to
look at the high energy part of the
spectrum so what are these used for well
ultraviolet is used in sunbeds to help
you get a suntan and it's also used in
special security inks because they
absorb ultraviolet and emit visible
light x-rays obviously are used to look
for broken bones in hospitals and
finally gamma rays are used to kill
bacteria in food to keep it fresh longer
to sterilize surgical equipment and also
to kill cancer cells in radiotherapy now
this is the high energy part of the
spectrum so there are dangers with using
these as you know too much exposure to
ultraviolet can cause skin cancer
now x-rays and gamma rays are even more
dangerous as they have enough energy to
remove an electron from an atom creating
an ion we call this ionization and this
can really damage cells I can actually
kill them or cause mutations in them
leading to cancer so exposure to high
doses of x-rays and gamma rays really
needs to be minimized it's okay when
you're just going for one or two x-rays
at the hospital but it's why the people
working in the hospitals need to take
extra precautions to minimize their dose
and that is the e/m spectrum make sure
you learn the entire electromagnetic
spectrum and the uses and dangers of
each part