Question

Real image of real object is formed by a convex lens. If the distance between real object and its real image is $80\text{cm}$, then power of lens may be

• A. $2D$
• B. $3D$
• C. $4D$
• D. $6D$

Answer 1

The correct option is D $6D$

When both the object and the image are real, then
$d>4f$ ($d$ distance between real object and real image)
$f<D/4$

$\frac{1}{f}>\frac{4}{d}$
As, $1/f=P$.
$P>\frac{4}{d}$

$P>\frac{4}{0.8}$

$P>5D$
$\Rightarrow P=6D$