A thin converging lens is found to form an image of a distant building 24 cm from the lens.If an insect is now placed 16 cm from this lens,how far FROM THE INSECT will its image be formed?
A) 64 cm
B) 72 cm
C) 32 cm
D) 96 cm
E) 48 cm

Question

Quizplus · Accepted Answer

Using the thin lens formula,
1/f = 1/do + 1/di
where f is the focal length of the lens, do is the distance of the object from the lens, and di is the distance of the image from the lens.

Given: do = 16 cm, di = ?, f = ?

Since the object is placed closer to the lens than the image, we know that the lens is acting as a magnifying glass, and therefore it is a converging lens. This means that the focal length is positive.

To find the focal length, we can use the fact that the lens forms an image of a distant building 24 cm away. When the object is at infinity, the image is formed at the focal point of the lens.

1/f = 1/do + 1/di
1/f = 0 + 1/24
f = 24 cm

Now we can use the thin lens formula again to find the distance of the image from the lens when the object is at 16 cm.

1/24 = 1/16 + 1/di
di = 32 cm

Therefore, the image of the insect will be formed 32 cm from the lens, so the answer is (C) 32 cm.

A Thin Converging Lens Is Found to Form an Image