Question

an object is placed perpendicular to the principal axis of a convex lens of focal length 20cm. the distance of the object from the lens is 30cm.
find the 1)position
2)the magnification
3)the nature of the image formed.

Answer 1

hope this help u.......

Answer 2

Answer:

(1) The image is 60 cm to the right of the lens.

(2) Magnification=-2.

(3)Nature of image=real and inverted.

Explanation:

As the lens is convex the focal length will be positive.

We will use two formulas to solve this question.

The first one is the lense formula i.e.

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

Where,

v=image position from the lens

u=object position from the lens

f=focal length of the lense

Now the second one is,

$m=\frac{v}{u}$                 (2)

m=magnification

From the question we have,

f=+20cm

u=-30cm

By substituting the values of f and u in equation (1) we get;

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

$\frac{1}{v}+\frac{1}{30}=\frac{1}{20}$

$\frac{1}{v}=\frac{1}{20}-\frac{1}{30}=\frac{3-2}{60}=\frac{1}{60}$

$v=+60cm$       (∴The positive sign shows that the image is formed on the right side of the convex lens, so the image formed is real)

Now by placing the required values in equation (2) we get;

$m=\frac{60}{-30}=-2$

Hence, (1)the image is 60 cm on the right side of the lens,(2)the magnification is -2, and (3)the nature of the image is real and inverted.