A doctor has prescribed a corrective lens of power +1.5 D. Find the fo

1.	A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
Answer» $\bf{\underline{Given}}:-$ <P> Lens of power (p) = 1.5 D $\bf{\underline{To\:Find}}:-$ The FOCAL length of the lens. $\bf{\underline{Solution}}:-$ we know that, $\blue{\bigstar}\:\:{\underline{\boxed{\bf\red{Power\:(p)=\dfrac{1}{f\:(in\:metres)}}}}}$ $\rm\longrightarrow\:1.5=\dfrac{1}{f}$ $\rm\longrightarrow\:f=\dfrac{1}{1.5}\:m$ $\rm\longrightarrow\:f=\dfrac{1}{1.5}\times\:10\:m$ $\rm\longrightarrow\:f=\cancel\dfrac{10}{15}\:m$ $\rm\longrightarrow\:f=\dfrac{2}{3}\:m$ $\rm\longrightarrow\:f=0.67\:m$ Hence,the focal length of the lens will be 0.67 m. The power of this lens is positive with a plus sign therefore,this is a convex lens or converging lens. $\blue{\bigstar}\:\:{\underline{\boxed{\bf\pink{More\: Information}}}}$ ➝ Power of lens :- The power of a lens is DEFINED as the reciprocal of its focal length in metres. A lens of short focal length has more power WHEREAS a lens of long focal length has less power. The unit of power of lens is dioptres. A power of convex lens is positive.

A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

Answer»

$\bf{\underline{Given}}:-$

<P>

Lens of power (p) = 1.5 D

$\bf{\underline{To\:Find}}:-$

The FOCAL length of the lens.

$\bf{\underline{Solution}}:-$

we know that,

$\blue{\bigstar}\:\:{\underline{\boxed{\bf\red{Power\:(p)=\dfrac{1}{f\:(in\:metres)}}}}}$

$\rm\longrightarrow\:1.5=\dfrac{1}{f}$

$\rm\longrightarrow\:f=\dfrac{1}{1.5}\:m$

$\rm\longrightarrow\:f=\dfrac{1}{1.5}\times\:10\:m$

$\rm\longrightarrow\:f=\cancel\dfrac{10}{15}\:m$

$\rm\longrightarrow\:f=\dfrac{2}{3}\:m$

$\rm\longrightarrow\:f=0.67\:m$

Hence,the focal length of the lens will be 0.67 m.

The power of this lens is positive with a plus sign therefore,this is a convex lens or converging lens.

$\blue{\bigstar}\:\:{\underline{\boxed{\bf\pink{More\: Information}}}}$

➝ Power of lens :- The power of a lens is DEFINED as the reciprocal of its focal length in metres.

A lens of short focal length has more power WHEREAS a lens of long focal length has less power.