An object of height 2.1cm is placed 0.9meters away from a double convex lens. Th

Question

An object of height 2.1cm is placed 0.9meters away from a double convex lens. The absolute value of the focal length of the lens is 1.8m.

a) What is the focal length of the double convex lens?

b) What is in m the position of the image formed by the lens?

c) What is the type of image formed?
1)real, upright, and enlarged 2) real, inverted, and enlarged 3) real, upright, and reduced
4) virtual, upright, and enlarged 5) virtual, inverted, and enlarged 6) virtual, upright, and reduced

A second double convex lens is placed 0.9m away from the first lens on the opposite side of the object (object

Explanation / Answer

a) +1.8 m

b) 1/s1 + 1/s1' = 1/f1

(1/0.9) + (1/di) = (1/1.8)

s1' = -1.8 m       <<---------answer

position of the image formed by the lens = 1.8 m

c) 4)virtual, upright, and enlarged      <<---------answer

d) s2 = 1.8+0.9 = 2.7 m            <<---------answer

e)

1/s2 + 1/s2' = 1/f2

(1/2.7)+(1/s2') = 1/f2

f2 = 5.4 m         <<---------answer

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