Why is focal length of light of yellow colour taken as geometric mean of focal length of light of red and violet colours when a ray of white light passes through a lens?

An oscillator consists of a block of mass 512 g connected to a spring. When set into oscillation with amplitude 34.7 cm, it is observed to repeat its motion every 0.484 s. Find (a) the period, (b) the frequency, (c) the angular frequency, (d) the force constant, (e) the maximum speed, and ( f ) the maximum force exerted on the block.

A PLANE TRANSMISSION GRATING HAS 45000 LINES. DETERMINE ITS RESOLVING POWER IN THE SECOND ORDER FOR WAVELENGTH OF 5000A.

A PLANE TRANSMISSION GRATING HAS 45000 LINES. DETERMINE ITS RESOLVING POWER IN THE SECOND ORDER FOR WAVELENGTH OF 5000A.

If V-numer of a multi mode fiber is 3. Calculate the no.of modes if it is step index and graded index fiber multimode fiber (rounded off)?

What is the difference between angular position and angular fringe width... I always get confused .