This is the diagram of entire
electromagnetic spectrum.
Electromagnetic spectrum here
includes all the wavelengths
that we encounter.
For example, the common waves
that we normally use is,
again, here the radio waves.
Radio waves are long waves.
And the microwaves are a little
bit shorter here.
And we have the visible light.
That is the light that we use to
see each other, and we can
see things in this range.
And we have, on the
other hand--
on the extreme right here--
the hard x-rays and
gamma rays.
These are the rays that
we don't see everyday.
However, they have a lot
of energy, and we
can feel the effects.
The same way here, radio
waves are long waves.
The wave, it goes up and down.
Wave travels like this.
The distance between the two
peaks is the wavelength.
The wavelength here is
10 to the 3, which is
1,000 meters long.
And on this side, on the hard
x-rays and gamma rays, you can
see the wavelength is only 10
to the minus 12, which is
very, very short.
And this also implies that the
frequency with which the wave
goes up and down like
this-- up and down--
again, the frequency is very,
very low here, which is only
10 to the 6th, which is a
million times it goes up and
down in a second.
And on this side where the
x-rays are, you can see it is
10 to the 20, which is 1
followed by 20 zeros.
So the frequency is very high.
Obviously what we can see from
this is as the frequency
increases here, the wavelength
is decreasing.
Or the shorter the
waves, obviously
the higher the frequency.
And what we can say about energy
is that these waves,
which are very, very short here,
or in other words, very
high frequency, tend to have
very high energy content here.
You can see energy content
is measured.
Energy of one photon
is measured
here in electron volts.
This is a million electron
volts here for x-rays and
gamma rays, whereas here it is
10 to the minus 9, which is 1
over a billion, which
is very, very less.
So what we learn from this
is these long waves--
the radio waves, et cetera--
don't have that much energy.
Whereas the x-rays and gamma
rays which have high frequency
and short wavelength, they are
very high energy content.
And that's the reason they have
very high energy content.
And that's the reason they can
penetrate through our bodies
and so on and so forth.
