Photo Emissive Cell:
The photo emissive cell consists of a glass envelope with a vacuum inside.
The envelope also contains a light sensitive cathode and an anode.
When light strikes on a photo emissive cell, the radiation causes the cathode negative electrons to be emitted which are attracted by the positive anode and a current to flow (photoelectric effect).
The value of this current is proportional to the intensity of light falling on the cathode.
Photo Cell:
It is a device for measuring or detecting light or other electromagnetic radiation, since its electrical state is altered by the effect of light.
Construction:
It is constructed up of a lamp box containing bulb, a micro ammeter, a photocell and a ruler to measure the distance between the lamp box and the micro ammeter.
Working:
When we switch on the bulb the rays of light emitted from the bulb goes out and strikes the photocell which shows some deflection on the micro ammeter. We note down the current and the distance in order to study the ratio of current striking the photocell.
In this experiment we use two bulbs, one is of 60 w and the other is of 100 w. We observe the two distances in order to calculate the average so that our result can be accurate.