Saved Bookmarks
| 1. |
Three coherent point sources `S_(1),S_(2) and S_(3)` are placed on a line perpendicular to the screen as shown in the figure. The wavelength of the light emitted by the sources is lambda. The distance between adjacent sources is `d=3lambda` The distance of `S_(2)` from the screen is D`(gtgt lambda)`. Find the minimum (non zero) distance x of a point P on the screen at which complete darkness is obtained. A. `(2sqrt(2)D)/7`B. `sqrt((17)D)/8`C. `4sqrt(5)D`D. `(4sqrt(2)D)/7` |
|
Answer» Correct Answer - B for nearest minima `dsintheta=8lambda//3 (i.e.2lambda//3+lambda+lambda) Rightarrow 3lambdasintheta=8lambda//3 Rightarrowsintheta=8//9` `Rightarrow tantheta=D//x=8/sqrt(17)Rightarrowx=sqrt(17D)/8` |
|