DAY 18 – DAW January

Fresnel diffraction: half-period zones and zone plates, circular aperture.


Q 1. Show that the areas of all the half-period zones are nearly the same. Find the radius of 1st half-period zone in a zone plate whose focal length is 50 cm and the wavelength of the incident light is 500 nm. [15 marks]

Q 2. The radius of the first zone in a zone plate is 2mm. What will be the position of the first image of a point source of light of wavelength  500 nm placed at a distance of 5 m from the zone plate? [10 marks]

Video Solution at 11 pm