Saved Bookmarks
| 1. |
Findout the equivalent focal length of the combenation of lenses shown in the figure. Surrounding medium is air. |
|
Answer» Solution :`1/f_(1)= (mu_(l)/mu_(s)-1)(1/R_(1)-1/R_(2))` `=(1.5-1)(-1/10-1/10)` `=0.5 xx(-2)/10` `rArr f_(1)=10/(0.5xx-2)=-10` cm `1/f_(2)=(mu_(l)/mu_(s)-1)(1/R_(1)-1/R_(2))` `=(4/3-1)(1/10+1/10)` `rArr 1/f_(1)=1/3 (2/10)` `rArr f_(2)=(30/2)=15` cm `f_(3)=-10` cm `1/f_(eq)=1/f_(1)=1/f_(2)+1/f_(3)` `=1/15-2/10` `rArr f_(eq) =150/(-20)=-7.5` cm |
|