MCQ
Find magnification for lens. focal lenth is $25\;cm$
- A$2$
- ✓$5$
- C$7$
- D$12$
✓
Answer
Correct option: B.
$5$
b
Consider the lens equation.
Consider the lens equation.
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
Substitute the values.
$\frac{1}{v}-\frac{1}{20}=\frac{1}{25}$
$\frac{1}{v}=\frac{1}{25}-\frac{1}{20}$
$=\frac{4-5}{100}$
$v =-100$
The magnification is given as,
$m =\frac{ v }{ u }$
$=\frac{-100}{-20}$
$=5$
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