1a. A 73.3 mm focal length lens is used to focus an image on the photographic fi

Question

1a. A 73.3 mm focal length lens is used to focus an image on the photographic film in a camera. The maximum distance allowed between the lens and the film is 120.0 mm. How far in front of the film should the lens be placed in order to photograph an object 6.4 m in front of the lens? Give your answer in mm to 3 sf.

1b. Two converging lenses have 27.7 cm focal length, and are placed 16.2 cm apart. An object is placed 35.4 cm in front of one. Where will the final image formed by the second lens be located? Give your answer in cm to 3 sf.

1c. A movie star catches a reporter shooting pictures of her at home. She claims the reporter was trespassing and to prove her point, she gives as evidence the film she seized. Her 1.73 m height is 8.28 mm high on the film, and the focal length of the camera lens was 200.0 mm. How far away from the subject was the reporter standing? Give your answer to 3 sf.

Explanation / Answer

a) 1/f = 1/Do + 1/Di

1/0.0733m = 1/6.4m + 1/Di

Di = 74.15 mm

b) The location, v of image by the first lens is given by
1/v - 1/(-35.4) = 1/27.7 or v = 127.3 cm beyond first lens.
The new object distance from second lens = 34.5.- 127.35 = -92.84 cm on the right of second lens. The new image distance, V as measured from secind lens is given by
1/V - 1/(92.84) = 1/27.7 or V = 21.33 cm on th right of the second lens

c) x / 1.73 = 200 / 8.28
x = 41.79 m

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