Two thin lens of focal lengths $f_{1}$ and $f_{2}$ are in contact. The focal length of this combination is

\frac{f_{1} f_{2}}{f_{1} - f_{2}}

No worries! We‘ve got your back. Try BYJU‘S free classes today!

\frac{f_{1} f_{2}}{f_{1} + f_{2}}

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

\frac{2 f_{1} f_{2}}{f_{1} - f_{2}}

No worries! We‘ve got your back. Try BYJU‘S free classes today!

\frac{2 f_{1} f_{2}}{f_{1} + f_{2}}

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B $\frac{f_{1} f_{2}}{f_{1} + f_{2}}$
If resulting focus is $f$ then $\frac{1}{f} = \frac{1}{f_{1}} + \frac{1}{f_{2}}$

which lead us to $f = \frac{f_{1} f_{2}}{f_{1} + f_{2}}$
Option B is correct.

Suggest Corrections

Similar questions

f_{1}

f_{2}

If two thin lenses of focal length f₁ and f₂ are held in contact then the focal length of the combination will be

∣ ∣ ∣_{1} \times_{2} ∣ ∣ ∣ =_{1} ._{2}

∣ ∣ ∣_{1} +_{2} ∣ ∣ ∣

f_{1}

f_{2}

M - 1

M - 2

f_{1}

f_{2}

Join BYJU'S Learning Program