Three converging lenses of focal length 3.50 cm are arranged with a spacing of 1

Question

Three converging lenses of focal length 3.50 cm are arranged with a spacing of 1.83·101 cm between them, and are used to image an insect 1.83·101 cm away.

a) Where is the image?

b) Is it real or virtual? Is it upright or inverted? Please state whether the following statements are true or false:

1.The final image is real T/F
2.The final image is on the right side of the third lens T/F
3.The final image is on the left side of the third lens T/F
4.The final image is inverted T/F
5.The final image is upright T/F
6.The final image is virtual T/F

Explanation / Answer

This needs to be done one lens at a time. The image from the first will be the object of the second and the image of the second, the object of the third until the fianl image is formed

Lens 1

1/f = 1/p + 1/q

1/3.5 = 1/18.3 + 1/q

q = 4.33 cm

Since the lenses are 18.3 cm apart, 18.3 - 4.33 = 13.97 cm from the second lens

1/3.5 = 1/13.97 + 1/q

q = 4.67 cm

That distance is 18.3 - 4.67 = 13.63 cm from the third lens

1/3.5 = 1/13.63 + 1/q

q = 4.71 cm to the right of the third lens

Part B)

The image is a real image since all values of q were positive (especially the last one)

The image will be inverted since the first lens will invert it, the second will flip it back upright, and the third will re-invert it.

Statement 1 is True

Statement 2 is True

Statement 3 is False

Statement 4 is True

Statement 5 is False

Statement 6 is False

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