Question

Find the power of convex lens of focal length 40cm.​

Answer 1

Answer:

length = 40 cm f =f/r

r=2 therefore 40/2 =20

Answer 2

Answer:

$\green{ \underline \bold{Have \: Given:- }} \\ \\ \implies \: Focal \: lenth \: of \: convex \: lens \\ \\ f = + 40cm \: = \frac{40}{100} meter \\ f = + 0.4 \: meter \\ \\ \because \: \: \: { \bold{ Power \: of \: lence}} = \frac{1}{f} (in \: meter) \\ \\ = \frac{1}{ + \: 0.4} \\ = + \: 2.5 \: meter \\ \\ \bold \blue{⟹ So, Power \: of \: convex \: lence \: is \: + 2.5 \: D} \\ \\ \bold \red{(D \: or \: Diopter \: is \: unit \: of \: power \: which \: equals \: to \: 1/meter)}$