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) $200 \mathrm {~cm}$

Question

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The Answer of 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) $200 \mathrm {~cm}$

A Drawing Is Placed 40 cm40 \mathrm {~cm}40 cm In Front of a Thin Lens

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