It's not a real world problem I think, the question is probably designed for us to research about focal length and understand afocal systems as well.
But you wrote six lenses, wouldn't 325mm be for seven lenses?
So if I understand you correctly, the first lens would be at the left edge of the tube. And the image will be 25mm to the right of the tube when rays are coming from the left. And since it's 50mm between each of the seven lenses the tube will be 300mm long. Then shouldn't the focal length be...
I'm sorry, but I still don't understand. So if the focal length is finite, it will be the distance from the lens equivalent to where the rays converge (25mm after the last lens). But where is the lens equivalent? At the position of the first lens? Then the focal length would be 50mm*6+25mm =...
Thank you again!
So we have learned that if you extend the rays that have come through the last lens, they should cross where the rays originally came from at the position of the lens equivalent. And the distance from the lens equivalent to the focal point is the effective focal length. This...
Thank you for the reply. I'm thinking that since the rays converges at 25mm after the last lens it should mean that the effective focal length should be 25mm. The system is only repeating so the last lens should have the same effect on the rays as only a single 25mm lens. Or am I wrong?
So we have the focal lengths:
f1, f2, ..., f7 = 25mm
And the distance between the lenses:
d1-2, d2-3, ..., d6-7 = 50mm
I have figured out that if the system would be afocal if it had an even number of these lenses. This is because the focal length of two adjacent lenses is the same as the...