Question

Infrared light of wavelength 2.5 µm illuminates a 0.20-mm-diameter hole. What is the angle of the first dark fringe in radians? In degrees?

Answer 1

Θ=0.01525 rad

or

Θ=0.87°

Step-by-step explanation:

Given data

wavelength λ=2.5 µm =2.5×10⁻⁶m

Diameter d=0.20 mm =0.20×10⁻³m

To find

Angle Θ in radians and degree

Solution

Circular apertures have first dark fringe at

Θ=(1.22λ)/d

Substitute the given values

So

Θ=[1.22(2.5×10⁻⁶m)]/0.20×10⁻³m

Θ=0.01525 rad

or

Θ=0.87°