If a laser beam is red with a wavelength of 632.8 nm, what is the angle from the center of the airy disk to the first dark ring?

Answer

given,

wavelength of laser light = 632.8 nm

assuming that aperture of lens be equal to dia = 1 mm

now,

When laser light passes through aperture diffraction of light takes place

The first diffraction minima occurs at

where a is the width of aperture

λ is the wavelength of light

p is the angle

               p = 0.0363° angle of the first dark ring

a and c

c is 100% but i am confused in a