Two converging lenses are placed in line with each other. An upright object is p

Question

Two converging lenses are placed in line with each other. An upright object is placed 30 cm away from the first lens which has a focal length of 12 cm and produces an inverted image 1cm in height that is 20 cm from the first lens. The second lens has a focal length of 30 cm and the two lenses are 60 cm apart. Determine the height of the final image and whether it is inverted or upright with respect to the original object. See the diagram below Height of final image Type of image Upright or Inverted (Relative to original object)

Explanation / Answer

Here, 1/u + 1/v = 1/f

=> 1/v = 1/12 - 1/30

=> v = 20 cm

=> 1/v1 = 1/30 - 1/40

=> v1 = 120   cm

=>   first magnification = - 20/30   = - 0.666

=> second magnification =    - 120/40   =   - 3

=> total magnification = 3 * 0.666 = 2

=>    height of final image =   1 * 3   = 3 cm

=> type of image = real

=> upright image is formed .

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