The ray diagram shows the image of an object formed by a converging lens. What is the focal length of the lens?

90 cm

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72 cm

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50 cm

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40 cm

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Solution

The correct option is D 40 cm
According to the rules of image formation through a convex lens, a ray passing through the focus, after refraction, goes parallel to the principal axis

We can see that the ray at the bottom goes parallel to principal ais after refraction

Hence it must be passing through the focus

The point at which the incident ray hits the principal axis is located at 40 cm from the lens

Hence the correct answer is 40 cm.

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Similar questions

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Q. An object

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Q. (a) Find the position and size of the virtual image formed when an object 2 cm tall is placed 20 cm from:
(i) a diverging lens of focal length 40 cm.
(ii) a converging lens of focal length 40 cm.
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Q. (a) A small object is placed 150 mm away from a diverging lens of focal length 100 mm.
(i) Copy the figure below and draw rays to show how an image is formed by the lens.
Figure
(ii) Calculate the distance of the image from the lens by using the lens formula.
(b) The diverging lens in part (a) is replaced by a converging lens also of focal length 100 mm. The object remains in the same position and an image is formed by the converging lens. Compare two properties of this image with those of the image formed by the diverging lens in part (a).

Q. The ray diagram shows the image formation of an object by a converging lens. How far is the image formed from the lens.

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