Question

Rakhi conducts an experiment to produce an image of an object on a screen which is placed at 20 cm from the lens. She uses a convex lens of focal length 15 cm for the experiment.Where should she place the object in order to produce the sharpest image?​

Answer 1

Answer:

60cm

Step-by-step explanation:

lens formula ⇒ 1/f = 1/v - 1/u

f = +15cm (convex lens; RHS of lens)

v = +20cm (RHS of lens)

u = ?

putting values,

1/15 = 1/20 - 1/u

1/15 - 1/20 = -1/u

1/60 = -1/u

∴ u = -60cm (LHS of lens)

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Answer 2

Given:

The placed at$20 cm$ from the lens she uses a convex lens of focal length $15 cm$.

To find:

The object in order to produce the sharpest.

Step-by-step explanation:

$v=20cm$

$f=15cm$

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

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

$\frac{1}{u} =\frac{1}{20} -\frac{1}{15}$

$=\frac{-1}{60}$

$u=-60 cm$

Answer:

Therefore, the object in order to produce the sharpest $-60cm.$