Photoelectric effect:-
according to quantum theory of light,
When electromagnetic waves propagate it carries energy in
packet or pieces ( it means that energy is quantized )
Electromagnetic energy carries in packet or pieces according
to quantum theory of light given by Einstein.
This packet of energy called photon and the energy of photon
is given by
E = hf,
where h is Planck's constant and f is the frequency.
ACCORDING TO ABOVE RELATION, amount of energy related to
frequency of that wave.
If we increase frequency we increase amount of energy (of
photon).
What quantum mechanics tell us about subatomic particle?
especially electron.
Electromagnetic waves carry amount of energy In the same way
, electron also carry some amount of energy.
As we study in chemistry, normally electron remain in ground
state (lowest level of energy) when some amount of energy given to electron and
it able to overcome coulomb force of attraction between electron and proton
.
then electron gets excited move in excited state but remain there temporary it
soon releases energy and return back to its ground state it releases energy in
the form of light.
Same phenomenon used by Einstein to give photoelectric
effect,
We all know about electrostatics force, proton in nucleus
pull electron with a coulomb force,in order to free electron we have to provide
more energy than that coulomb force.
Einstein conducted a experiment,
,he took a electron, He said that ,I shine light on my
electron and that light have low energy that not high enough to excite a
electron
Then he increase intensity of that light and find that
electron was not excited even now, then he said if light travels like a wave
(according to it energy of light proportional to it intensity i.e, more the intense of light ,more energy
it carries.)
If there is increase in energy, by increasing intensity my
electron must get excited. but that was not happen here.
Now, from quantum theory of light, we know that light
carries energy in the form of packet known as quanta energy it carries is given
as ,
E = hf,
where h is Planck's constant and f is the frequency.
From above equation we know that energy directly
proportional to frequency. what happens if we increase frequency of light in
above experiment .
Einstein reconduct the experiment and find that on
increasing the frequency electron gets excited .
IT MEANS
THAT LIGHT TRAVEL IN THE FORM OF PARTICLE
Photoelectric
effect gives experimental prove to quantum theory of light.
now, question arises what is photoelectric effect?
The photoelectric effect s the emission of electrons from the surface of matter generally, a metal in response to the incident light.
but in a condition that frequency of incident light must be greater than threshold frequency (it is a minimum frequency require to electron gets excited or gets free ).
Energy contained within the incident light is absorbed by electrons
within the metal, giving the electrons sufficient energy to be knocked
out or get free of the surface of the metal.
Continue reading with:
share us:-
