# Angular Width Of Central Diffraction

350nm falls on a single slit of width of 0.20mm. What is the angular width of the central diffraction peak?

I think that the width should be equal to 2Θ, where Θ=arcsin(m*λ/d).... m=1 and we have λ=350*10^-9 and d= 0.20*10^-6.....but when i do the calculations I get 1.75 and the arcsin is a maths error...Could anyone help me please?

## Answers and Replies

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blue_leaf77
Homework Helper
λ=350*10^-9 and d= 0.20*10^-6
Are those numbers in the same unit?

λ=nm and d= mm

TSny
Homework Helper
Gold Member
Note 1 mm ≠ 10-6 m.

Ok so I must have 10^-7 ?

blue_leaf77
You should have written the unit as well, if you write it correctly it will be $d= 0.20 \times 10^{-6}$ km. If you use km for d then you must also use km for $\lambda$.