Question

What is the energy of a single photon of infrared light with a wavelength of 1.00 µm? 1 µm = 10^-6m

A): 4.29 x 10^-20 J
B): 4.98 x 10^-19 J
C): 1.98 x 10^-19 J
D): 5.05 x 10^18 J

Answer 1

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°

And that’s why I think it might be C or D.