The two slits in Young's double slit experiment are illuminated by two different sodium lamps emitting light of the same wavelength. No interference pattern will be observed on the screen.

Options

A. (a) There will be no constant phase difference between the two waves
B. (b) The wavelengths are not equal
C. (c) the amplitudes are not equal
D. (d) None of the above

Answer

A

Explanation

In conventional light source, light comes from a large number of independent atoms, each atom emitting light for about `10^-9sec`, i.e., light emitted by an atom is essentially a pulse lasting for only `10^-9sec`. Light coming out from two slits will have a fixed phase relationship only for `10^-9sec`. Hence any interference pattern formed on the screen would last only for `10^-9sec`, and then the pattern will change. The human eye can notice intensity changes which last at least for a tenth of a second and hence we will not be able to see any interference pattern. Instead due to rapid changes in the pattern, we will only observe a uniform intensity over the screen.