Optics Answers

lights of wavelength 550 nm incidents normally on a diffraction grating with 2000 lines/cm. The ratio of transparent part a and non transparent part b is 1:2. Find:
1.the orders appearing the phenomena of missing order
2.How many orders of intensity maxima can be observed by this grating, list then one by one.
3. f the light falls on the gratings at 30 (slant up) angle to the normal , then what are the maximun orders which can be seen in both up and down directions?

In a double slit experiment two coherent sources have slightly
different intensities I and I+dI such that dI << I. Show that
resultant intensity at maxima is nearly 4I while that at the minima
is nearly (dI)^2 / 4I

In hilly areas television reception may be poor. To correct this problem the signal is often boosted by a local relay station before being re-transmitted. Sometimes this introduces further difficulties because of the interference between the incident and the re-transmitted signal. This can be avoided if the main transmitter emits waves that are vertically polarised.

Can someone explain to me why this would solve the problems of interference? Really very interested to know :) A detailed explanation would be good

A cubical vessel with opaque walls is so located that the eye of an observer does not see its bottom, but sees all of the wall CD. What amount of water should be poured into the vessel for the observer to see an object 'O' placed at a distance 10 m from the corner D?The face of the vessel is a = 40.