Photoelectric Effect - III

We might have seen a torch and light in a dark place.

A torch is a device that produces light from the bulb with the help of electric cells.

When we light a torch on a wall, the light falls, and instantly covers all the space at front of it.

At different points of the wall, the light falls suddenly at the same time.

And there is no time lag in falling light of the torch between two different points of the wall.

And the falling of torch light on the walls looks like a continuous wave but not like some particle of light falling in discrete manner.

Now to check light is a wave or a particle, a scientist named Hertz carried an experiment, we say it Hertz Experiment.

The set up of Hertz experiment consist of two metal plates, which was connected to a battery to apply a potential.

And when the metal plates exposed to light, it emits electrons and with the help of applied potential electrons get received at the second plate.

The process of emitting electron from a metal surface, when it exposed to light, we say it photoelectric effect.

And the minimum energy required by an electron to leave the metal surface, we say it work function.

The emitted electron associates some energy for a particular function, we say it maximum kinetic energy or .

Now the electron emitting from metal is something we say a particle which carry some mass, and the light hitting the metal is a wave.

Now lets discuss about light is a wave or light is a particle.

Consider a number of balls as particles and let we throw the balls a wall.

We see the hitting points by the ball on the wall is discrete in manner and doesn't occupy total space as by the torch light.

And the arriving of the ball at any point of the wall takes some time after the throw, we say it as a time lag.

While there is no time lag in receiving the light wave from the torch at any two different points on the wall.

And now the questions arises about light in our mind is about light i.e. the light is a wave or a particle.

Now an experiment was carried by a scientist, we say it young double slit experiment, it proves light as a wave.

And the conclusions made on the basis of Young double slit experiment, we say it as wave theory of light.

Now lets discuss about the photoelectric emission on the basis of wave theory of light.

The phenomenon of emission of electrons is an instantaneous process.

The emission of electron varies directly as the intensity of light falling on the surface.

And the was independent of intensity, where intensity is the energy of light falling per unit area, per unit time.

The increases linearly with frequency and below certain value of frequency, no emission takes place.

Where the frequency is the number of wave per second.

Revision.

When the metal plates exposed to light, it emits electrons, we say it as the photoelectric effect.

The emission of electron varies directly as the intensity of light falling on the surface.

The increases linearly with frequency and below certain value of frequency, no emission takes place.

The End.