(adsbygoogle = window.adsbygoogle || []).push({}); I can't figure out what I am doing wrong!!! Getting Frustrated!!

1. The problem statement, all variables and given/known data

A helium-neon laser (λ=629 nm) illuminates a diffraction grating. The distance between the two m=3 bright fringes is 33 cm on a screen 1.72 m behind the grating. What is the spacing between slits of the grating?

2. Relevant equations

Lamda = 629 nm

m = 3

y = 0.33 m

L = 1.72 m

d = ?

3. The attempt at a solution

What I did was tan theta = y/L = 0.33/1.72 = 1086 degrees

then I used the equation d*sin theta = m*lamda

and solved for d.... d = m*lamda/sin theta = 1.00x10^-5 m but I am getting it wrong...what am I not doing right???

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# Homework Help: I can't figure out what I am doing wrong Getting Frustrated

**Physics Forums | Science Articles, Homework Help, Discussion**