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 aYoungтАЩs double-slit experiment.
(a)┬аFind the distance of the thirdbright fringe on the screen from the central maximum for wavelength 650 nm.
(b)┬аWhat is the least distance fromthe central maximum where the bright fringes due to both the wavelengthscoincide?
Wavelength of the light beam,┬а
Wavelength of another lightbeam,┬а
Distance of the slits from thescreen =┬аD
Distancebetween the two slits =┬аd
(a)┬аDistance of the┬аnth┬аbrightfringe on the screen from the central maximum is given by the relation,
(b)┬аLetthe┬аnth┬аbrightfringe due to wavelength┬аand (n┬атИТ 1)th┬аbright fringe due towavelength┬а
┬аcoincide on the screen. Wecan equate the conditions for bright fringes as:
Hence, the least distance fromthe central maximum can be obtained by the relation: