A Drawing Is Placed $40 \mathrm {~cm}$ In Front of a Thin Lens

question 79

Multiple Choice

A drawing is placed $40 \mathrm {~cm}$ in front of a thin lens. If a virtual image forms at a distance of $50 \mathrm {~cm}$ from the lens, on the same side as the drawing, what is the focal length of the lens?

• A) \(- 45 \mathrm {~cm}\)
• B) \(+ 45 \mathrm {~cm}\)
• C) \(75 \mathrm {~cm}\)
• D) \(90 \mathrm {~cm}\)
• E) \(200 \mathrm {~cm}\)

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