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Home » Where should an object be placed in front of a convex lens of focal length 0.12 m to obtain a real image of size three times the size of the object, on the screen?
Where should an object be placed in front of a convex lens of focal length 0.12 m to obtain a real image of size three times the size of the object, on the screen?
Class 10 | ICSE | Physics | Refraction through a Lens | Selina
Where should an object be placed in front of a convex lens of focal length 0.12 m to obtain a real image of size three times the size of the object, on the screen?

Solution:

According to the question,

Focal length of the given convex lens is f = + 0.12 m

Magnification is m = -3 (real image)

For a lens, expression of magnification is

m = v / u

upon substituting values => – 3 = v / u

Therefore, v = – 3u

Expression for the Lens formula is,

1 / v – 1 / u = 1 / f

Upon substituting values we have ==> 1 / – 3u – 1 / u = 1 / 0.12

Or, -4 / 3u = 1 / 0.12

3u = -0.48 m

Or u = -0.48 / 3

Therefore, u = – 0.16 m

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