# Homework Help: Intensity and Interference of Light Beams

1. Aug 29, 2006

### aiglosicicle

i have to do a physics assignment and i got stuck at this quesion hope u guys can help.

An interference pattern is formed on a screen by the superposition of two coherent light beams, one of which has four times the intensity of the other. What is ratio of maximum to minimum intensity in the pattern?

Something i find very hard to understand is how intensity is related to inteference. I know that when the waves interfere constructively intensity is max and vice versa, but other than that i dont understand how else intensity is related to interference... for example... like how is the intensity of the maximas affected when slit separation is increased.

2. Aug 29, 2006

### Farsight

Maybe your question is in the wrong place, aiglosicicle, but nevermind. IMHO the question is easier than you think. Imagine you had two beams of the same unit intensity, creating an interference pattern. Then you add another three units of intensity to the second beam.

3. Aug 29, 2006

### Staff: Mentor

When coherent beams interfere constructively, their amplitudes add. Intensity of a beam is proportional to the amplitude squared.