1) Two converging lenses are placed 82 cm apart. An object is placed 1.848 m to
ID: 1774307 • Letter: 1
Question
1) Two converging lenses are placed 82 cm apart. An object is placed 1.848 m to the left of the first lens, which has a focal length of 20 cm. The final image is located 14 cm to the right of the second lens.
(a) What is the focal length of the second lens?
(b) What is the total magnification?
2) A camera uses a 164.0-mm focal length telephoto lens to take picture from a distance of infinity to as close as 2.00 m. What are the minimum and maximum distances from the lens to the films?
3) What is the focal length of a magnifying glass that gives an angular magnification of 6.00 when the image is at infinity?
Explanation / Answer
1st (left) lens's (intermediate) image is the 2nd (right) lens's object
u1 = -1.848 m; f1 = 0.20 m; separation = 0.82 m; f2 = ? ; v2 = 0.14m
Solving,
v1 = 1/(1/f1-1/u1) = 0.18 m
u2 = separation-v1 =0.64 m (-ve sign)
f2 = 1/(1/v2+1/u2) = 0.18 m
Final Image location relative to lens 2 = v2 = 0.14m
Final Image location relative to lens 1 = v2+sep = 0.96 m
Final Image location relative to object = v2+sep+u1 = 2.808m
Magnification = v1v2/(u1u2) = 0.021
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