An object is placed 28 cm to the left of a lens of focal length 15 cm.24 cm to the right of this lens is a plane mirror.Where does the final image form?

Question

Quizplus · Accepted Answer

First, we can use the lens formula 1/f = 1/v - 1/u where f = 15 cm, u = -28 cm (since the object is to the left of the lens) to find the image distance v = -11.67 cm. This negative value means that the image is formed to the left of the lens.
Next, we use the mirror formula 1/v' + 1/u' = 1/f where v' is the distance of the final image from the mirror and u' is the distance of the virtual object from the mirror. Since the light from the lens will reflect off the mirror and form a virtual object 24 cm to the left of the mirror, u' = -24 cm. f is still 15 cm, and we can solve for v' to get v' = -8 cm. This negative value means that the final image is formed 8 cm to the left of the mirror. However, since the mirror is to the right of the lens, we need to consider the sign convention for distances: distances to the right of the mirror are positive, while distances to the left of the mirror are negative. Therefore, the final image is actually formed 8 cm to the right of the mirror, which is answer choice B.

An Object Is Placed 28 Cm to the Left of a Lens