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## Saturday, July 3, 2021

### What is Quantum Theory of Radiation ?

Quantum Theory of Radiation:This theory was proposed by German physicist, Max Planck in 1900, to explain the phenomena of black body radiations. According to this theory;

“Energy is emitted or absorbed by a body not continuously but discontinuously in the form of small packets or bundles of energy known as Quanta. The energy of a body can increase or decrease by 1,2,3,4,5,…..n quanta but not by fractions of a quanta."

Thus, the energy of radiation is proportional to its frequency and inversely proportional to wave length.

Solved Questions:

### (3) A bulb emits light of wave length 4500Å. The bulb is rated as 150 watt and 8% of the energy is emitted as light. How many photons are emitted by the bulb per second?

Practice Questions:

1. A photon of light of wavelength 6000 Å has energy E. Calculate the wavelength of photon of a light which has energy/photon 4E.

2. Calculate the wavelength, wave number and frequency of photon having its energy 5 electron volt.

3. Iodine molecule dissociates into atoms after absorbing light of 4500Å. If one quantum of radiation is absorbed by each molecule, calculate the kinetic energy of iodine atoms. (Bond energy of I2 = 240 kJ mol–1)

1.     Lemda-2= 1500 Å

2.     2.475 × 10–5 cm, 4.04 × 104 cm, 1.212 × 1015 Hz

3.     2.16 × 10–20 J

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