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

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Homework Help Overview

The discussion revolves around calculating the diameter of the moon's image on a camera's film, given the focal length of the camera and the radius of the moon. Participants are exploring the relationship between object height, focal length, and image height in the context of lens optics.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants are questioning whether it is possible to calculate the image height with the provided information, noting the need for additional data such as the distance from the Earth to the moon. Some express uncertainty about how to apply the formulas they have.

Discussion Status

The discussion is ongoing, with participants offering insights about the assumptions related to the distance of the moon. Some suggest that treating the moon's distance as infinite could simplify calculations for image distance, while others emphasize that this assumption may not hold for determining image size.

Contextual Notes

There is a noted constraint regarding the missing distance information between the Earth and the moon, which is critical for solving the problem. Participants are also referencing external resources for this information.

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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