The image size of a distant object is simply its angular size multiplied by
the lens focal length.
1/f = 1/f₁+ 1/f₂−d/f₁•f₂.
f₁= 20 cm =0.2 m
f₂= - 8 cm = - 0.08 m
1/f = 1/0.2 – 1/0.08 - 1/0.2•0.08=
=5-12.5-62.5 = - 70
f= -1/70 =-0.0143 m
= -1.43 cm
h= 2•1.43 = 2.86 cm
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http://www.fulviofrisone.com/attachments/article/411/the%20light%20fantastic.pdf
Chapter 4.5.4 page 89
Telephoto lenses allow one to "zoom in" on distant objects, making them bigger. A particular telephoto lens consists of a combination of two thin lenses having focal lengths of f1=20 cm and f2=−8 cm, respectively. The lenses are separated by a distance of d=15 cm. Determine the image size in cm on the film plane, located at the back focal point of the lens system, of a distant object subtending an angle of α=2∘ at the camera.
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it's wrong !!!
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