Question

If the focal length of a convex lens is 20cm and the object distance is 18cm then what is the image distance?
And what is the magnification?

Answer 1

Refer to the attatched image.

:)

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@zaqwertyuioplm

Answer 2

Question:

If the focal length of a convex lens is 20 cm and the object distance is 18 cm then, what is the image distance?  And what is the magnification?

Answer:

• The distance of the image is 180 cm behind the mirror.
• The magnification of the image is 10.

Given:

The focal length of the lens is 20 cm.

The distance of the object is 18 cm.

To find:

• The distance of the image.
• The magnification of the image.

Explanation:

Focal length(f) = 20 cm.

The distance of the object(u) = 18 cm.

Let, the distance of the image be, 'v'.

We know that,

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

⇒ $\frac{1}{20} = ( \frac{1}{18} + \frac{1}{v})$

⇒ $(\frac{1}{20} - \frac{1}{18}) = \frac{1}{v}$

⇒ $\frac{1}{v} = ( \frac{1}{20}-\frac{1}{18})$

⇒ $\frac{1}{v} = (\frac{9-10}{180} )$ [∵ The L.C.M. of the denominators is 180.]

⇒ $\frac{1}{v} = -\frac{1}{180}$

⇒ v = - 180 cm.

∴ The distance of the image is 180 cm behind the mirror.

Let, the magnification of the image be, 'm'.

We know that,

$m = - (\frac{v}{u})$

⇒ m = $-(\frac{-180}{18})$

⇒ m = - ( - 10)

⇒ m = 10.

∴ The magnification of the image is 10.

For the similar content, follow the given link, as I have solved:

Of the focal length of a convex lens is 20 cm and the object distance is 18 cm then what is the image distance?  And what is the magnification?

https://brainly.in/question/15795300