How Is Angular Width Calculated in Lens Optics?

AI Thread Summary
To calculate the angular width of a scene focused by a converging lens, the focal length and the width of the image on the screen must be considered. The initial calculation of tan-1(37/50) yielding 36.5 degrees is incorrect because it assumes the distance to the object is equal to the focal length. Instead, the distance to the image must be determined first, which can be done using the lens formula. Once the correct distance is established, the angular width can be accurately calculated using the width of the image. Properly applying these principles will yield the correct angular width of the scene.
SamTsui86
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Homework Statement



A converging lens with a 50.0 mm focal length is used to focus an image of a very distant scene onto a flat screen 37.0 mm wide. What is the angular width of the scene included in the image on the screen?

Homework Equations





The Attempt at a Solution



Basically I just did tan-1(37/50) = 36.5

What are I doing wrong?
 
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Do you know how to calculate the height of the image as a function of it's distance form the lens? Use that to find get the distance and then use the distance and width to get the angle. Your problem is that you assumed that the distance was the focal length which isn't true.
 

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