We make a zoom lens with a converging lens followed by a diverging lens. The converging lens has focal length +12 cm, an

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We make a zoom lens with a converging lens followed by a
diverging lens. The converging lens has focal length +12 cm, and
the diverging lens has focal length -12 cm. If the separation
between the lenses is 6 cm, and the object is at infinity, how far
is the image from the second (rightmost) lens? (please answer in
cm)
If the first lens has a diameter of 4.2 cm, what is the f number
of the light after the second lens? f/ ...