Question

Photograph of the ground ar taken form an air-craft ,flying at an altutude of 2000m by a camera with a lens of focal length`50cm`.The size of the film in the camera si `18xx18cm`.What area of the ground can be photography by this camera at any one time.

Answer 1

As here`u=-2000m,f=0.50m`,So from lens formula`(1)/(v)-(1)/(u)=(1)/(f)`,we have
`(1)/(v)-(1)/(-2000)=(1)/(0.5)`
`(1)/(v)=(1)/(0.5)-(1)/(2000)~=(1)/(0.5)[as(1)/(0.5)gt gt(1)/(2000)]`
`v=0.5m=50cm=f`
Now as in case of a lens
`m=(v)/(u)=(0.5)/(-2000)=-(1)/(4)xx10^(-3)`
So `I_(1)=(ma)(mb)=m^(2)A`
`[because A=ab]`
i.e,`A=(I_(1))/(m^(2))=(18cmxx18cm)/([(1//4)xx10^(-3)]^(2))=(720mxx720m)`