The Total solution for NCERT class 6-12
A beam of light consisting of twowavelengths, 650 nm and 520 nm, is used to obtain interference fringes in aYoung’s double-slit experiment.
(a) Find the distance of the thirdbright fringe on the screen from the central maximum for wavelength 650 nm.
(b) What is the least distance fromthe central maximum where the bright fringes due to both the wavelengthscoincide?
Wavelength of the light beam,
Wavelength of another lightbeam,
Distance of the slits from thescreen = D
Distancebetween the two slits = d
(a) Distance of the nth brightfringe on the screen from the central maximum is given by the relation,
(b) Letthe nth brightfringe due to wavelength and (n − 1)th bright fringe due towavelength
coincide on the screen. Wecan equate the conditions for bright fringes as:
Hence, the least distance fromthe central maximum can be obtained by the relation: