# Reflection grating

1. Homework Statement
http://img244.imageshack.us/img244/6852/phys24xy.png [Broken]

2. Homework Equations
d=1/N d*sin(theta)=m*(lambda)

3. The Attempt at a Solution
d=1/1970
d=.0005076

.0005076*sin(theta)=2*600e-9

sin(theta)=.0000012/.0005076

arcsin(.002364)=.135º

*sigh*
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution

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hage567
Homework Helper
One thing I see is that when you found d you didn't convert from cm to m, so you have inconsistent units in your equation.

d=.0005076cm = .000005076m

.000005076*sin(theta)=2*600e-9

sin(theta)=.0000012/.000005076

arcsin(.2364)=13.7º

Anything else I'm missing, because the answer is not 13.7º?

hage567
Homework Helper
Why do you have m=2? If it is first order I would think it would be m=1.

hage567
Homework Helper
Are you sure you are using the right equation? I think the grating equation you are using is not quite right for the conditions of your problem. The one you are using is a special case where the angle of incidence is normal to the grating. You need to include the angle of incidence in your equation. So your equation would be
d*(sin(theta(m)) - sin(theta(inc))) =m*lamda. where m = ±1 for first order maxima. Anyway see if that helps.