Question

An object is placed at a distance 20 cm from a convex lens and a real image is obtained at a distance 60cm from the lens. The focal length of the lens is___​

Answer 1

FINAL ANSWER:-

$f=30cm$

GIVEN:-

• object is placed at a distance(u)⇒ -20 cm

• convex lens and a real image is obtained at a distance(v)⇒ -60cm

TO FIND:-

focal length of the lens

FORMULAS USED:-

• $\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

SOLUTION:-

convex lens and a real image is obtained at a distance of -60 , here '-'ve is taken because it's said that real and inverted image so image is form downward principal axis .

so,

f=?

v=-60

u=-20

let's put it in equation

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\frac{1}{f}=\frac{-1}{60}-(\frac{-1}{20})\\\frac{1}{f}=\frac{-1}{60}+\frac{1}{20}\\\frac{1}{f}=\frac{-1+3}{60}\\\frac{1}{f} =\frac{2}{60} \\\frac{1}{f}= \frac{1}{30} \\f=30cm$

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Answer 2

maihuunknown ne sahi answer diya hai use brainlist bana