Saved Bookmarks
| 1. |
In `u-v` method to find focal length of a concave mirror, if object distance is found to be `10.0 cm` and image distance was also found to be `10.0 cm`, then find maximum permissible error in (f). |
|
Answer» Correct Answer - C Using the mirror formula, `1/v+1/u=1/f` we have, `1/(-10)+1/(-10)=1/f` `rArr f=-5` or `|f|=5 cm` Now, differentiating Eq. (i). we have, `(-df)/(f^2)=-(du)/(u^2)-(dv)/(v^2)` This equation can be written as `|Deltaf|_(max)=[(|Deltau|)/(u^2)+(|Deltav|)/(v^2)](f^2)` Substituting the values we get, `|Deltaf|_(max)=[(0.1)/((10)^2)+(0.1)/((10)^2)](5)^2=0.05 cm` `:. |f|=(5+- 0.05)cm`. |
|