# Question: Is the focal length of convex lens is 20 cm find the power of lens?

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## What is the power of convex lens of focal length 20 cm?

The power of a lens of focal length 20cm is 5D.

## What is the power of concave lens having focal length 20 cm?

So, the power of a concave lens is (-5 D).

## What is the power of convex lens of focal length 25 cm?

Answer: Power is expressed as the inverse of focal length, where a focal length of 1 meter is equal to one diopter. So a 25 cm. focal length (0.25 meters) has a power of 4 diopters.

## What is the power of convex lens of focal length 40 cm?

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination is. P=1f=1f1+1f2=10.4+1-0.25=-1.5diopter.

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## What will be the power of lens if its focal length is given as 20 m?

For example, if the focal length of a lens is 20cm, that is 0.2m To find the power of this lens, take the reciprocal of 0.2 and we get 5. Therefore the power of this particular lens is 5D.

## What is the power of concave lens of focal length 25?

f=-25cm As P=100f,f=100-25=-4dioptre.

## Which lens has a negative focal length?

For a convex lens, focal length (f) is positive and for a concave lens, the value of f is negative.

## What is the power of convex lens of focal length 0.5 Metre?

P = 1/f = 1/0.5 = +2 D.

## What is the power of concave lens of focal length 50 cm?

= 100/50 = 2 dioptre.

## How do you calculate the power of a convex lens?

The diopter is the unit of measure for the power of a lens. Convex lens power is defined as the ability of the lens to converge the rays of light which fall on it as shown in the below figure. It can mathematically be defined as P = 1f, where f is the focal length.

## What is the power of a lens with focal length of 10cm?

Hence, the power of the lens is \$10\$ dioptre. Note:The power of a lens is measured in dioptre if and only if the focal length is in meter since diopter is a S.I unit.

## What is the power of the focal length is 40 cm?

The focal length of a concave lens is equal to -2.5 D

Hence in the above case it is given that the focal length is 40cm or 0.4m. So the power =- 1/0.4= -2.5D the sign is used to determine the type of lens used.

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## When a real object is placed at 25cm from a lens a real image is formed?

If the object is between the focus and pole no real image will be formed. Since the object is at 25 cm from the lens, the focal length of the object should be less than 25 cm because to form a real image the object must be at a larger distance than the focal length.