Lenses: If given object height and focal length, is it possible to calculate

AI Thread Summary
To calculate the diameter of the moon's image on a camera's film using a focal length of 35 mm and the moon's radius, the distance to the moon must be considered. While the distance can be treated as infinite for image distance calculations, it is crucial for determining the image size. The relevant formulas involve the lens formula and magnification, which require the actual distance to the moon for accurate substitution. Users are directed to external resources for the moon's distance from Earth to facilitate these calculations. Accurate image height determination hinges on both the focal length and the distance to the moon.
Byrne
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the image's height? If so, how? I have the formulas, but see no way of making a substitution.

If you wanted to know the problem, it states:

The focal length of a camera is 35 mm and the radius of the moon is 1.74 x 106 m. Calculate the diameter of the moon's image that appears on the camera's film.
 
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It's impossible to solve the problem using only the given information. However, if you look up the distance between the Earth and the moon from somewhere...
 
Byrne said:
the image's height? If so, how? I have the formulas, but see no way of making a substitution.

If you wanted to know the problem, it states:

The focal length of a camera is 35 mm and the radius of the moon is 1.74 x 106 m. Calculate the diameter of the moon's image that appears on the camera's film.

Take the moon's distance from the Earth to be infinite.
 
HallsofIvy said:
Take the moon's distance from the Earth to be infinite.
For the purpose of calculating the image distance from the lens, the distance to the moon can be considered infinite. But not for the purpose of calculating the image size on the film.
 

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