Question

A lens produces a magnification of -5. Is this a converging or diverging lens? If the focal length of the lens is 6 cm. Draw a ray diagram showing the image formation in this case.

Answer 1

Thus the lens will be converging lens.

Explanation:

• Magnification = -0.5
• Focal length = 6 cm
• Here, focal length is positive and magnification is negative.

The focal length is positive and magnification is negative of converging lens.

Using formula of magnification

m = v / u

Put the value into the formula

- 0.5=  v / u

v = - 0.5 u

Now, using formula of focal length

1 / f = 1 / v - 1 / u

Put the value into the formula

1 / 6 = 1 / -0.5 u - 1 / u

1 / 6 = - 1.5 / 0.5 u

u = - 18 cm

Put the value of u in formula of magnification

- 0.5 =  v / -18

v = 9 cm

Thus the lens will be converging lens.