Question

The image of an object which is 10cm from a lens is formed on the same side as the object. If the image is 10cm behind the object, Find the focal length of the lens.

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Answer 1

Focal length is 6.67 cm.

Step-by-step explanation:

Object distance, u, from the lens = 10 cm

Image distance, v, to the lens = 10 cm + 10 cm

= 20 cm

Apply the lens formula to determine the focal length, f, of the lens.

`(1)/(f)` =
`(1)/(u)` +
`(1)/(v)`

=
`(1)/(10)` +
`(1)/(20)`

=
`(2 + 1)/(20)`

`(1)/(f)` =
`(3)/(20)`

Find the inverse of both sides, so that;

f =
`(20)/(3)`

= 6.67

f = 6.67 cm

The focal length of the lens is 6.67 cm.