Planck's quantum theory - Practice Questions & MCQ

Atom and molecules could emit (or absorb) energy only in discrete quantities known as quanta and not in a continuous manner. The following are certain phenomenon which could not be explained by the wave nature of electromagnetic radiation and are explained by the particle nature:

1. The nature of emission of radiation from hot bodies (black -body radiation).

2. Ejection of electrons from a metal surface when radiation strikes it (photoelectric effect).

3. Variation of heat capacity of solids as a function of temperature.

4. Line spectra of atoms with special reference to hydrogen.

Max Planck suggested that the energy which is emitted or absorbed by the black body is not continuous but discontinuous in the form of small discrete packets of energy. Each such packet of energy is called a ‘quantum’. In case of light, the quantum of energy is called a ‘photon’. The energy of radiation is proportional to its frequency ($\nu$) and is expressed by  the following equation: 

                                        $E=h \nu=\frac{h c}{\lambda}$

where h is the Planck's constant and it has a value equal to 6.63 $\times$ 10^-34 J-s