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In Young's double slit experiment ,momochromatic light of wavelength 630 nm illuminates the pair of slits and produces an interface pattern pattern in which two consecutive bright frings are separated by 8.1 mm. Another source of monochromatic light produce the interface pattern in which the two consecutive bright fringes are seperated by 7.2mm, find the wavelength of light from the second sources . What is the effect to on the interference fringes if the monochromatic sources is replaced by a source of white light ? |
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Answer» Solution :Here `lambda_(1)=360 nm =630xx10^(-9)m,beta_(1)=8.1 mm` `=8.1xx10^(-3)` `lambda=?,beta_(2)=7.2 mm=7.2xx10^(-3) m` Let `d` be the width and `D` be the distance between slit and SCREEN then `beta_(1)=(lambda_(2)D)/(d) and beta_(2)=(lambda_(2)D)/(d)` `THEREFORE (beta_(1))/(beta_(2))=(lambda_(1)D)/(d)xx(d)/(lambda_(2)D)=(lambda_(1))/(lambda_(2))` `(8.1xx10^(-3))/(7.2xx10^(-3))=(630xx10^(-9))/(lambda_(2))` `(8.1)/(7.2)=(630xx10^(-9))/(lambda_(2))` `therefore lambda_(2)=(7.2xx630xx10^(-9))/(8.1)=560xx10^(-9)m` `=560 nm`. Whenthe monochromatic source is replaced by a source of white light, the fring width is changed. |
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