Question

A 500 nm laser shines through 2 slits separated by 1 mm producing interference fringes on a screen 3 m away.

1) Calculate spacing between fringes in mm

2) if laser power decreases, will this increase/decrease/same for fringe spacing?

3) If laser power= 1 mW, calculate number of photons that hit the screen in 1 second

4) Calculate time it takes a photon to travel from slits to screen in ns

5) Calculate how low laser power needs to be in pW to prove that a photon interferes with itself instead of other photons

Answer 1