First slide

The lens

Question

When a real object is placed at 25cm from a lens, a real image is formed. Mark the Incorrect statement from the following

Moderate

A

The lens is a converging lens
B

The image may be magnified or diminished
C

The focal length of the lens is less than 25cm
D

The focal length of the lens may be greater then 25cm

Solution

Since a real image is formed, the light rays must converge after refraction from lens.
Hence it is a converging lens
Thus the focal length is positive
For formation of image of an object at distance 25cm
From lens equation, $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$
$\Rightarrow \frac{1}{v} - \frac{1}{- 25} = \frac{1}{f}$
$\Rightarrow \frac{1}{v} = \frac{1}{f} - \frac{1}{25}$
Since the lens in converging, v is positive
Hence $f < 25 cm$
Magnification = $\frac{v}{- 25}$ which may be greater than or less than 1 depending upon the focal length

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App