# Double slit interference

1. Feb 26, 2006

### G01

Light of wavelength 600nm passes through two slits separated by .2mm and is observed on a screen 1.0m behind the slits. The location of the central max is marked on the screen and labeled $$y_0$$

A) at what distance are the m = 1 bright fringes. I got this part. the answer is .003m or 3mm.

B) A very thin piece of glass is placed over one hole, causing the light in that hole to move slower. The light is delayed by 5.0 X 10^-16s. What fraction of the wave period is this. It is 1/4 of the wave period. I got this as well.

C) The phase difference? The one wave is delayed by 1/4 of a period, so the phase difference is pi/2.

D) Which way does the central max move and how far. I know it moves toward the glass covered hole, but I can't figure out how far. Can anyone help me to figure out how to proceed with this part. Even a small hint will help. Thank you.