Question

A convex lens has a focal length of 30 cm. An
object is kept in front of it at a distance of
90 cm. Find the distance of the image from the
lens. What type of image is formed? ​

Answer 1

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$\maltese \: It \: is \: given \: that$

• Focal length = 30cm
• Image distance = ?
• Object distance = 90cm

Now according to mirror formula :

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

$f = \frac{uv}{u + v}$

After inputting the known values here we get :

$30 = \frac{ - 90v}{90 - v}$

$2700 - 30v = - 90v$

$2700 = - 90v + 30v$

$2700 = - 60v$

$v = \frac{ - 2700}{60}$

$v = 45$

Therefore the image is formed at 45cm away from pole of mirror.

Since convex mirror always forms a virtual erect and diminished image, so this will also be same in this case .

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BY SCIVIBHANSHU

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