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## Homework Statement

This is a question we have been doing at school. The answer is C. I think A is correct as well

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## Homework Equations

I have used nλ=dsinθ and put in test values.

I guess I should be able to do this by just 'inspecting the question' but the sin confused me. So I put in some test values as below.

## The Attempt at a Solution

When I used 600nm for wavelength and 100,000 lines per meter the first order and second orders are at 3.4398 degrees 6.8921degrees. Doubling N then gives 6.8921 and 13.8865 degrees. This suggests that a is right... so what am I doing wrong please

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