You visited us 1 times! Enjoying our articles? Unlock Full Access!

Combinations of Lenses & Mirrors

In the adjoin...

Question

In the adjoining ray - diagram are given the positions of an object O, image I and two lenses $L_{1}$ and $L_{2}$ . The focal length of $L_{1}$ is also given. Find the focal length of the lens $L_{2}$

30 c m

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

- 30 c m

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

- 15 c m

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

None of these

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

Open in App

Solution

The correct option is C $- 15 c m$
For lens $L_{1}$
$\frac{1}{v} - \frac{1}{u} = \frac{1}{f},$
$f = + 15 c m u = - 40 c m$
put these values
$\frac{1}{v} - \frac{1}{- 40} = \frac{1}{15}, v = + 24 cm$
This image acts as object for lens $L_{2}$
So, $u = + (24 - 14) = + 10 c m$ ,
$v = 30 c m$
$f = ?$
put the values
$\frac{1}{f} = \frac{1}{v} - \frac{1}{u} \Rightarrow \frac{1}{f} = \frac{1}{+ 30} - \frac{1}{+ 10}$
$f = - 15 c m$

Suggest Corrections

Similar questions

Q. In the adjoining ray - diagram are given the positions of an object O, image I and two lenses

L_{1}

and

L_{2}

. The focal length of

L_{1}

is also given. Find the focal length of the lens

L_{2}

3 lenses L1, L2 and L3 each of focal length 30 cm are placed coaxially .an object is held at 60cm from the optical centre of lens L1.the final image is formed at the focus os L3.Calculate the separation between 1) L1 and L2 2) L2 and L3

Q. You are given three lens

L_{1}, L_{2}, L_{3}

each of focal length

15 c m

. An object is kept at

20 c m

in front of

L_{1}

, as shown. The final real image is formed at the focus

^{'} I^{'}

L_{3}

. Find the separations between

L_{1}, L_{2}

and

L_{3}

Q. In the figure given, there are two convex lens

L_{1}

and

L_{2}

having focal length of

f_{1}

and

f_{2}

respectively. The distance between

L_{1}

and

L_{2}

will be:

Join BYJU'S Learning Program

In the adjoining ray - diagram are given the positions of an object O, image I and two lenses L1 and L2. The focal length of L1 is also given. Find the focal length of the lens L2

The correct option is C −15 cmFor lens L1 1v−1u=1f, f=+15 cmu=−40 cm put these values 1v−1−40=115,v=+24 cm This image acts as object for lens L2 So, u=+(24−14)=+10 cm, v=30 cm f=? put the values 1f=1v−1u⇒1f=1+30−1+10 f=−15 cm

In the adjoining ray - diagram are given the positions of an object O, image I and two lenses $L_{1}$ and $L_{2}$ . The focal length of $L_{1}$ is also given. Find the focal length of the lens $L_{2}$