# Photoelectric Effect

Definition: It is defined as a phenomenon in which electron start ejecting from the surface of the metal when the light of suitable frequency strikes on it, is called the photoelectric effect.

Experiment
Apparatus used in this experiment are evacuated chamber, metal (potassium, rubidium , cesium  these metals held electrons loosely so you can observe this experiment on these metals easily by using visible light to humans) , Battery, Detector

Observation from the experiment :
• When the light of suitable frequency strikes on the metal surface. The metal starts ejecting electrons immediately there is no time delay.
• Light of suitable frequency is need to do photoelectric effect .If the frequency of light is below the threshold it will not produce a photoelectric effect no matter how many hours you strike the surface with light
• The No. of electrons ejected from the metal surface per second depend on the brightness/intensity of the light  not on the frequency
• The kinetic energy of electron emitted by the surface of the metal per second depends on the frequency of light (frequency of light must be greater than or equal to the threshold frequency as per the material) it does not depend on the brightness or intensity of the light

Lets take a numerical for better understanding to understand observation 3 and 4

Suppose you have a 100-watt bulb that emits electromagnetic light of wavelength 400nm. Calculate the no. of photons emitted per second by the bulb

Solutions : Energy emitted by the buld is 100watt that is 100J/s
we know that
 $E = h \vartheta$