A thin plastic sheet of refractive index 1.6 is used to cover one of the slits of a double slit arrangement. The central point on the screen is now occupied by what would have been the 7th bright fringe before the plastic was used. If the wavelength of light is 600 nm, what is the thickness (in µm) of the plastic sheet ?
7
4
8
6
A.
7
The change in path length = (µ − 1) t. This path length change the position of bright fringe upto seventh bright fringe. The thickness of plastic substance inserted in the path of rays will must be 7 (on assuming fringe width to be units).
Find the right condition(s) for Fraunhoffer diffraction due to a single slit.
Source is at infinite distance and the incident beam has converged at the slit.
Source is near to the slit and the incident beam is parallel
Source is at infinity and the incident beam is paralle
Source is near to the slit and the incident beam has converged at the slit