# Homework Help: Find Wavelengh - Young't Double Slit

1. Nov 4, 2009

### partly

1. The problem statement, all variables and given/known data
For light from a discharge lamp, the first-order bright fringe is observed at a perpendicular distance of 2.35cm from the mid-point of the slits, when the slit-to-screen distance is 1.2m and the slit separation is 0.03mm. What is the wavelengh of the light from the lamp?

2. Relevant equations
Wavelength = xd/D

3. The attempt at a solution
x = 0.0235m, d = 0.00003m, D = 1.2m

Wavelength = xd/D = (0.0235x0.00003)/1.2 = 7.05x10^-7/1.2 = 5.875x10^-7m

Not quite sure where I've gone wrong ..or if I was even on the right path. If you could offer some assistance it would be much appreciated :) (p.s. hi, nice forum ^^)

2. Nov 6, 2009

### Redbelly98

Staff Emeritus

There might be an issue with the number of significant figures in your answer, but other than that it looks correct to me. Why do you think it is wrong?

3. Nov 8, 2009

### partly

I had the wrong figures in my head for the wavelength of visible light. My answer fits in there quite comfortably as it happens.