In YDSE, slits are $0.589 \mathrm{mm}$ apart. If a sodium vapour lamp of wavelength $589 \mathrm{nm}$ is used, then angular width of central maxima is

Explain the statement ‘light added to light can produce darkness.’

In Young’s double-slit experiment, light of wavelength $5000 \text{Å}$ is used. The third bright band on the screen is formed at a distance of $1 \mathrm{cm}$ from the central bright band. If the screen is at a distance of $1.5 \mathrm{m}$ from the centre of the two narrow slits, calculate the separation between the slits.