A laser beam has the following important characteristics:

1. Directionality: An ordinary source of light emits light waves in all the directions and is highly divergent. But the divergence or angular spread of a laser is very small.

2. Monochromaticity: It means that all the laser rays have same wavelength and frequency when they are emitted from the same source.

3. Brightness: A laser beam has brightness many times in magnitude greater than that of conventional sources due to high directional property of laser beam.

4. Coherence:Two or more light waves are said to be coherent if they bear a constant phase relation among themselves. Coherence can be classified into two ways:

a) temporal coherence

b) spatial coherence.

Do you know the difference between the two?

Do you know about the spontaneous and stimulated emission?

Think, we will discuss it later on!!