state the laws of photo electric emission
Answers
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The four laws of photoelectric emission are given as : LAW 1 : For a given metal and frequency, the number of photoelectrons emitted is directly proportional to the intensity of the incident radiation. LAW 2: For a given metal, there exists a certain frequency below which the photoelectric emission does not take place
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Answer:
Definition: When the beam of the light enlightens the surface of the metals like sodium, potassium, caesium and rubidium then their electrons start emitting. The phenomenon of emission of electrons is known as the photoelectric emission.
Explanation:
other words, the photoelectric emission is the process through which the free electrons are liberated from the surface of metals when it absorbs light. The photoelectric emission depends on the frequency of light and not on the intensity of light.
Some metals like alkaline, sodium, etc. require very less energy for moving the electrons from their surfaces. Or we can say their work function is very less. When the light energy incident on the surface of that metals, the electrons gets energised and starts emitting. The electrons which emitted through this way is known as the photoelectrons. And the current which induces because of the photoelectrons is known as the photoelectric current.
The number of electrons emitted depends on the intensity of light fall on the surface and the frequency of their radiations. This property of metals also used for measuring the intensity of light incident on the surface.
Consider the figure below shows the phenomenon of photoelectric emission. The emitter and the anode are enclosed in the evacuated glass tube G. The anode is made of thin metal and is kept at the positive potential concerning the emitter. When the light incident on the surface of metal then the electrons start ejected from the emitter surface. The electrons moved towards the positive anode and established the current in the external circuit. The flow of electrons is maintained till the illumination is continue.The energy of photons incident on the surface depends on the frequency of the light and is expressed as,equation-1
where ‘h’ is the plank’s constant and their value is equal to the 6.626Χ10-34 joule-second, f shows the frequency of light in the hertz.
The energy requires for emission of electrons = eΦ
Where e – electrons charge and φ – work function of electrons in volts.
Hence the photons which cause emission is given by the expressionphotoemission- equation-2