# Revise GCSE Physics

Question:What kind of beam of light does a laser produce?

A laser produces a narrow beam of light that does not spread out, of a single colour (monochromatic), that is coherent and has high intensity. We call this an intense,coherent, low-divergence, monochromatic beam.

Intenity is a measure of how concentrated the power of a beam of light is made.

Intensity can be increased in two ways.

1. Increase the power of the source of light.

2. Decrease the size of spot of the beam of light.

Remember that power = energy transferred per second

Coherent means that all the indivdual waves(or particles) in the beam of light are 'in sync'; they are lined up so that they interact with the material at the same time and therefore have greater effect by adding together. Non coherent beams have particles that arrive randonly and have no additive effect.

More formally: Intensity if the energy per second per unit of area of the cross section of the beam of light. Units would be Joules per second per metre squared or Watts per meter squared.