Hello guys,
have ever wondered why do we can see an object? If your answer is because we have
eyes, of course that will be so true. But what about if I say “have you ever
wonder why do we can see many colors? Like green, orange, pink, yellow and
others. I meant how could we make a difference between those all? If your
answer is because they have different colors, or you say that because of light.
Then I’ll say that’s not wrong. You know guys light is just the small part of
electromagnetics wave. As a human being we can only see a visible light which
is part of electromagnetics wave. And this is a very big advantage for us, we
can imagine whats gonna happen when we are able to see every invisible light or
able to see every waves in this life. As we know that wave is a propagating
vibration. So what will happen, when you’re hearing a music, you wont enjoy the
music because of the waves are going every where and you’re going crazy with
it,, haha :D , even you wont be close to anybody because of her or his wave
when he speaks. We’re still talking about the wave from his sound, not about
the bacterial or viruses yet since we know that our mouth is one of bacterial
source :D … or when you get your phone is ringing, when your friend who calls
you saying something then you wont get the phone near your ear, because you see
the wave out of the phone :D . And surely when those all happen, this life wont
be joyful, no communication, no friends, and no others. but there is the truer
answer. What is it? Are you getting excited? All right keep reading hehe ^^
Ok here we
go, Why do we can see different colors in object? Thats we gonna find out this
time. its perfectly simple, the answer is just keep reading… hehe.
Well to
answer such a problem like that above, we should understand about Black Body
Radiation. Ok what is black body radiation? To answer this we must first take a
look at what make us see object? We see them because there is a reflection in the material. Well, let me give you an
example to make you understand easier. For example, we see a green object like
a tree? That means there is just the green wavelength that is reflected and
every other wavelength is absorbed by the tree. Another cases, if you have
favorite clothes, its blue. You love it so much, you wish to wear it every time
you wanna go. If I ask you again? How could you see blue on your clothes? Simply,
you just need to say that, your clothes only reflects blue wavelength and
absorbs every other wavelength.
So the object
will be black, means no light will be reflected every wavelength is absorbed by
the object. So does happen in the white object. If you find a white object,
means every wavelength is reflected, and no wavelength is absorbed by the object.
But there is interesting here, why is it called black body radiation?
The thermal
radiation emitted by a hot body, in general, depends on the composition and the temperature of the body. However, there is a class of bodies,
called black bodies, which emit thermal radiation whose quantity and quality depend only on their
temperature. For this reason the radiation emitted
by such bodies is called the thermal radiation. Such bodies are named black
bodies because they absorb all the radiation that falls
on it. Lamp black and platinum black are nearest to ideal black bodies. When a black body is maintained at constant high
temperature, the emitted radiation is called
the black body radiation. For experimental purposes a cavity having a small
hole can be regarded as a perfect black body because of its
identical behavior with that of the perfectly black body. If radiation is allowed to enter such a cavity, it is reflected back
and forth at the inner walls of the cavity
and at each reflection some portion of energy is absorbed. After suffering a
large number of reflections at the walls it is completely
absorbed in the cavity. Therefore at lower temperature the hole appears black. When the cavity is maintained at higher
temperature the radiation that comes out of the
hole is similar to that emitted by a black body at the same temperature. Thus,
a cavity with a small hole acts like a black body.
So that’s the reason why its called black bodyradiation. Now you can understand well isn’t is?