Properties of light

Coherence:

• The light from a laser is said to be coherent, which means the wavelengths of the laser light are in phase in space and time.
• Laser light is highly coherent.
• All emitted photons have constant phase relationship i.e. they are in same phase.

Monochromaticity:

• Monochromatic light means the light of only one wavelength (frequency).
• There is no frequency difference between photons. So laser beam is monochromatic beam.
• The light emitted from a laser is monochromatic,that is, it is of one wavelength.
• In contrast, ordinary white light is a combination of many different wavelengths.

Directional:

• Lasers emit light that is highly directional.
• Ordinary light, such as coming from the sun, a light bulb, or a candle, is emitted in many directions away from the source.
• Laser light is emitted as a relatively narrow beam in a specific direction.

Unidirectionality:

• Laser light is highly directional.
• It can travel large distances without any spreading. Laser beam, is very narrow as compared to ordinary light.

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Brightness:

• Laser beam is extremely intense that light form any other sources when laser is focused at focused at a point.