State two conditions to obtain sustained intereferance.

What is interference of light? Write two essential condition for sustained interference pattern to be produced on the screen.

State two application of beats.

State two conditions for two light sources to be coherent. Derive an expression for the fringe width in Young.s double slit experiment for interfernce with suitable diagram.

State two benefits of mitosis.

State the conditions resulting in reverse osmosis?

State the condition of total internal reflection. Calculate the speed of light in the medium whose critical angle of 45^@ .