Civil Engineering - UPSC Civil Service Exam Questions - Discussion

5. 

A 3000 m long line lying at an elevation of 450 m measures 10 cm on a vertical photograph.
The focal length of the camera is 21 cm. The scale of the photograph for the area having an elevation of 1000 m will be

[A]. 1 : 27381
[B]. 1 : 25008
[C]. 1 : 20606
[D]. 1 : 30421

Answer: Option A

Explanation:

No answer description available for this question.

Patel Bhai said: (Oct 3, 2017)  
Please give the explanation.

Sam said: (May 9, 2018)  
Here, S = f/(H-h).

Manish K Soni said: (May 21, 2018)  
Give an explanation of the solution.

Rashid Shahab said: (Apr 25, 2020)  
For 1st case.
Scale = 10/(3000 *100) = 1/30000.
Now,
1/30000 = 0.21/(H - 450).
You get flying height, H = 6750m.

For 2nd case.
Scale = f/(H - h).
Scale = 0.21/(6750 - 1000) = 1 in 27381.

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