An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and nature of the image formed.

Question

Philoid · Accepted Answer

A converging lens means a convex lens. The diagram is shown below:

Here, Object distance, u = -25 cm

Image distance, v = ? (To be calculated)

And, Focal length, f = + 10 cm (because it is convex lens)

Now, putting these values in the lens formula:

Thus, the position of image is at a distance of 16.67 cm from the lens. The plus sign for image distance shows that the image is formed on the right side of lens (or behind the lens) and that the nature of image is real and inverted.

Let us calculate the magnification now. For a lens:

Magnification,

We will now calculate the size of image h2 by knowing the size of object h1 and value of m:

Now, m =

So, -0.66 =

h2 = -0.66 5 = -3.3 cm

Thus, the size of image is 3.3 cm. The negative sign of the size of image shows that the image is inverted.