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- Homework Statement
- Please see the attached photo

- Relevant Equations
- P (rad) = sigma e0 T^4

At long distances, images due to convex lenses are formed at the foci.

I know that the Sun is at a very far distance from the lens, so I assume the rays are parallel and the image is formed at the focus (500mm away from the centre of the lens).

How do I calculate the diameter of the image?

The hint to solving this problem says that "The angular diameters of object and image are equal". What is the "angular diameter", and what does the hint mean? If the light rays intersect at a focal point, how can there even be a diameter? Furthermore, how is the fact that the lens diameter = 100mm useful?

I am quite confused by this question, any help is appreciated. Thank you!