A photograph of a landscape is captured by a drone camera at a height of $18$ km. The size of the camera film is $2 ext{ cm} imes2 ext{ cm}$ and the area of the landscape photographed is $400 ext{ km}^2$. The focal length of the lens in the drone camera is :

Question

A photograph of a landscape is captured by a drone camera at a height of $18$ km. The size of the camera film is $2	ext{ cm}	imes2	ext{ cm}$ and the area of the landscape photographed is $400	ext{ km}^2$. The focal length of the lens in the drone camera is :

Dr. Abubacker · Accepted Answer

[Solution by Dr. Abubacker] The ground side is $\sqrt{400}=20$ km, the film side is $2$ cm, so the linear magnification is $m=\frac{2	ext{ cm}}{20	ext{ km}}$. For a distant object $v\approx f$, so $m=\frac fu\Rightarrow f=18	ext{ km}	imes\frac{2	ext{ cm}}{20	ext{ km}}=1.8$ cm. Answer (1).

Q. A photograph of a landscape is captured by a drone camera at a height of $18$ km. The size of the camera film is $2\text{ cm}\times2\text{ cm}$ and the area of the landscape photographed is $400\text{ km}^2$. The focal length of the lens in the drone camera is :

Explanation

Reviewed by Dr. Abubacker

Want to attempt the full paper?