Diffraction of Light through Single Slit

[samdiah]

Homework Statement

Monochromatic light falls into slit 3.00*10^-6 wide. The angle between the first dark fringes on either side of the cental maximum is 25 derees. Calculate the λ.

w=3.00*10^-6 m
ө=25˚

Homework Equations

sin(ө) = nλ/w
sin(ө) = ((m+0.5)λ)/w
Δy=λL/w

The Attempt at a Solution

sinө=λ/w
λ=sin25*3.0*10^-6
=1.3*10^-6 m

hoever the answer is 6.49*10^-7

 

[samdiah]

Please help its really easy I just don't get the concept!

 

[Doc Al]

The angle between the first dark fringes on either side of the cental maximum is 25 derees.

You have misinterpreted the angle. You are given the angle between the first dark fringes, but in the equation sin(theta) = n lambda/w, theta is the angle of the dark fringes measured from the central maximum.