An aircraft flying at a altitude of 2000 metre, takes the photographs of the ground by a camera with a lens of focal length 0.5 m. The size of the film in the camera is `12 cm xx 12 cm`. What area of the ground can be photographed by this camera at any time ?

Options

A. `240 m xx 240 m`
B. `300m xx 300 m `
C. `400 m xx 400m `
D. `480 m xx 480m`

Answer

D

Explanation

Given : `u=2000 m (-ve), f=(1)/(2)m`,
Size fo the film `=12xx12` cm
`because (1)/(v)-(1)/(u)=(1)/(f)`
`therefore (1)/(v)=(1)/(u)+(1)/(f) = -(1)/(2000)+(1)/(1//2) =2-(1)/(2000)`
`therefore (1)/(v)=(3999)/(2000) therefore v=(2000)/(3999)=(1)/(2)m`
`therefore M=(I)/(o)=(v)/(u)=(1)/(2xx2000) =(1)/(4000)`
`therefore o=4000I`
or size of the object = 4000 (size of the image)
`therefore` As the photographic plate is of dimensions `12cm xx 12 cm`, the area of the ground that can be photographed `=(12xx4000 cm) xx (12 xx 4000) cm`
`therefore " Area"=480m xx 480 m`