Two slits are made one millimeter apart and the screen is placed one meter away. What is the fringe

Question

Two slits are made one millimeter apart and the screen is placed one meter away. What is the fringe separation when the blue-green light of wavelength 500 nm is used?

Professor PC Thomas Classes · Answer

Fringe separation $\beta = \frac{\lambda D}{d} = 0.5 	ext{ mm}$.