| S. No |
Spontaneous Emission |
Stimulated Emission |
| 1 |
When an atom in an excited state E2 jumps to lower energy state E1 emitting a photon, without any external influence. Then this transition is called spontaneous emission. |
When an atom in an excited state E2 jumps to lower energy state E1 emitting a photon, it emits an additional photon of same frequency of incident photon. This transition is known as stimulated emission. |
| 2 |
The emitted photon can move in any random direction. |
The emitted photon travels in the same direction in which the incident photon is moving. |
| 3 |
Emission of photons takes place without energy. |
Emission of photons takes place with energy. |
| 4 |
The radiation given out by such a source will be incoherent. |
The radiation given out by such a source will be highly intense, monochromatic and coherent. |
| 5 |
Polychromatic radiation.(having many wavelength). |
Monochromatic radiation.( having a single wavelength ) |
| 6 |
Low intense |
High intense |
| 7 |
Less directionality and having more angular spread during propagation. |
High directionality and less angular spread during propagation. |
| 8 |
Example: Light from sodium or mercury vapour lamp. |
Example: Light from laser source. |
