What are the laws of photoelectric effect?

Answer 1

1 photoelectric current is propotional to the intensity of incident light

2 for a given material their exist a certain minimun frequency of light so that photoelectron can be ejected 4m metal surface.

3 the rate at which electron r emitted 4m a photo cathode i impedent of its temp.

4 time tag bet. the incident radiations and the emission of electron is less than 10 to power (-ve) 8.

Answer 2

The laws of radiation are:

1. Kirchoff's law of radiation : It states that good absorbers are good radiators.Mathematically, the ratio of spectral emissivity to the absorption power for the given wavelength is same for all bodies.

2. Prevost's law : Prevosts law of exchange states that

(a)Each body emits out energy at each temperature.

(b)The radiated amount of energy depends on the nature of body and its temperature.

3. Stefan's Boltzman law : The law states, "the total amount of energy radiated by the unit area in one second by a body is proportional to the fourth power of its absolute temperature.

4.Newton's cooling law : It states that if the temperature difference between the body & its surrounding is not very large , the rate of heat loss by the body is directly proportional to the difference in temperature of the body from its surroundings.

5. Wien's law : It describes the character of energy distribution law of black body for two absolute temperatures.

6. Planck's law : The black body spectrum was explained by Planck by his quantum theory given in 1900, according to which energy is emitted or absorbed by a body in the forms of photons each of definite energy E = hv.

7. Solar constant : It is the quantity of solar radiation incident normally per minute on 1 cm2 surface of a perfectly black body on the Earth. Its value is 1.93 cal/cm2 .

Answer 3

1. For a light of any given frequency, photoelectric current is directly proportional to the intensity of light, provided the frequency is above the threshold frequency.

2. For a given material, there is a certain minimum (energy) frequency, called threshold frequency, below which the emission of photoelectrons stops completely, no matter how high is the intensity of incident light.

3. The maximum kinetic energy of the photoelectrons is found to increase with increase in the frequency of incident light, provided the frequency exceeds the threshold limit. The maximum kinetic energy is independent of the intensity of light.

4. The photo-emission is an instantaneous process. After the radiation strikes the metal surface, it just takes 10--9 s for the ejection of photoelectrons.