Saved Bookmarks
| 1. |
A Fresnel's biprism arrangement is set with sodium light (lambda = 5893 Å) and in the field of the eyepiece we get 62 fringes. How many fringes shall we get if we replace the source by mercury lamp using , (a) green filter (lambda=5461 " "A^(@)) (b) violet filter (lambda = 4358 A^(@)) |
|
Answer» Solution :The fringe width p given by : p = DX/d ... (1) In the given PROBLEM, D and d are constant and hence there will be a change in fringe widthnwhen there is a change in the wavelength of light USED. When the source-is replaced by mercury light and” a green filter is used (the wavelengthsay `lambda_(1)= 5461 Å`) Let fringe width in this case be `beta_(1)` The width of field of view = 62 `beta` From equations (1) and (2), `beta/beta_(1) = lambda/lambda_(1) ...(3)` The width of field of view = 62 `beta` Suppose using a green filter, the field of view contains `n_(1)` FRINGES. Then width of field of view =`n_(1)beta_(1)` `62 beta = n_(1)beta_(1)` or `n_(1)=62(beta//beta_(1))= 62 (lambda//lambda_(1))=62 xx (5893xx10^(-8))/(546 xx 10^(-8))=67` (b)Letthe field of view contains `n_(2)` fringes using a violet filter wavelength. `(4358xx10^(-8))/(4358xx10^(-8)) =84` |
|