Question

A spectrally filtered helium lamp operates at 587.5 nm with a linewidth of 1.2 nm. The light emitted from the
lamp is focused by a lens onto a pin hole of 80 micron diameter. The light on the other side of the pin hole is
collimated by a second lens and is incident on a Young’s double slit apparatus with a slit spacing of 0.13 mm
which is located 1.5 m from the pin-hole source. Determine the visibility of fringes around the order m = 50.

Answer 1