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A convex lens is of focal length 10 cm. ...

A convex lens is of focal length 10 cm. What is its power?

A

`+10D`

B

`+5D`

C

`-10D`

D

`+1D`

Text Solution

Verified by Experts

The correct Answer is:
A
Here, the focal length of the lens is given in 'centimeters' so to calculate the power of this lens, we should first convert the focal length into 'meters' because our formula uses the focal length in 'meters'.
Now, 10 cm`=10/100`m ltbrge`0.1`m
So, Focal length, f`=0.1`m (A convex lens has positive focal length)
Now, putting this value of focal length in the formula for the power of a lens.
`P=1/(f"in metres")`
We get, `P=1/0.1`
or `P=(1 xx 10)/(1)`
Thus, Power, P=`+10` dioptres (or `+10`D)
Thus, the powerof this convex lens is `+10` dioptres which is also written as `+10`D. The plus sign with the power indicates that it is converging lens or convex lens.
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