Calculate the focal length of the thin lens shown in figure. The points $C_{1}$ and $C_{2}$ denote the centres of curvature. Refractive index of lens is $1.5$ .

$20 c m$

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

$40 c m$

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

$60 c m$

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

$80 c m$

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

Open in App

Solution

The correct option is B
$40 c m$

Given:
Refractive index, $μ = 1.5$
Radius of curvature of first surface, $R_{1} = 10 c m$
Radius of curvature of second surface, $R_{2} = 20 c m$
This is because the first surface is more curved and due to sign convention.

The focal length is given by:
$\frac{1}{f} = (μ - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$
$\frac{1}{f} = (1.5 - 1) (\frac{1}{10} - \frac{1}{20})$
$f = 40 c m$

Suggest Corrections

Similar questions

Calculate the focal length of the thin lens shown in figure. The points $C_{1}$ and $C_{2}$ denote the centres of curvature. Refractive index of lens is $1.5$ .

Q. In figure the points

C_{1}

and

C_{2}

denote the centres of curvatures then the focal length of the thin lens

(μ = 1.5)

Q. Calculate the focal length of the thin lens shown in the figure. The points

C_{1}

and

C_{2}

denote the centres of curvature.

Q. Figure shows a lens of refractive index

μ = 1.5

C_{1}

and

C_{2}

are the centres of curvature of the two faces of the lens of radii of curvature

10 cm

and

15 cm

respectively. The lens behaves as a

Join BYJU'S Learning Program

Calculate the focal length of the thin lens shown in figure. The points C1 and C2 denote the centres of curvature. Refractive index of lens is 1.5.

Calculate the focal length of the thin lens shown in figure. The points $C_{1}$ and $C_{2}$ denote the centres of curvature. Refractive index of lens is $1.5$ .