Question

If an object is placed $10 \,cm$ in front of a concave mirror of focal length $20\, cm$, the image will be

• A. diminished, upright, virtual
• B. enlarged, upright, virtual
• C. diminished, inverted, real
• D. enlarged, upright, real

Answer 1

Answer: (B)

$u=-10 \,cm \,f=-20 \,cm$ Using mirror formula,
$\frac{1}{f}=\frac{1}{v}+\frac{1}{u}-\frac{1}{20}=\frac{1}{v}+\frac{1}{(-10)}$
$\therefore \frac{1}{v}=-\frac{1}{20}+\frac{1}{10}=\frac{1}{20} v=20 \, cm$
Magnification $(m)=-\frac{v}{u}=-\frac{20}{(-10)}$
$=2$
Therefore, magnified (enlarged), upright and virtual image is formed.