Question

. A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal- length 20 cm. The distance of the object from the len is 30 cm. Find the: (i) position (ii) nature (iii) size of the image formed.

Answer 1

Answer: The size of the image is 10 cm and the image is real and inverted.

Explanation:

Given that,

Height of object h = 5 cm

Focal length f = 20 cm

The distance of the object u = -30 cm

Using lens's formula

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

$\dfrac{1}{20}=\dfrac{1}{v}-\dfrac{1}{-30}$

$\dfrac{1}{v}=\dfrac{1}{60}$

$v = 60$

The image is formed at 60 cm on the other side from the lens.

The magnification is

$m = \dfrac{v}{u}$

$m = \dfrac{60}{-30}$

$m = -2$

The image is real, inverted .

Size of the image,

$m = \dfrac{h'}{h}$

$-2 = \dfrac{h'}{5}$

$h' = -10 cm$

Hence, The size of the image is 10 cm and the image is real and inverted.

Answer 2

Explanation:

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