Click to Chat

1800-2000-838

+91-120-4616500

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
```        how to apply lense makers formula.i mean to say which one of the radii is taken first and which one after that.for example in this question.
calculate the focal length of a concave lens in water(r.f of water is 4/3)if the surfaces have radii equal to 40cm & 30 cm.R.F of glass is 1.5```
6 years ago

SAGAR SINGH - IIT DELHI
879 Points
```										Dear student,
It is a relation that connects focal length of a lens to radii of  curvature of the two surfaces of the lens and refractive index of the  material of the lens.
The following assumptions are made for the derivation:

The lens is thin, so that distances measured from the poles of its  surfaces can be taken as equal to the distances from the optical centre  of the lens.

The aperture of the lens is small.

Point object is considered.

Incident and refracted rays make small angles.

Consider a convex lens (or concave lens) of absolute refractive index m2 to be placed in a rarer medium of absolute refractive index m1.
Considering the refraction of a point object on the surface XP1Y, the image is formed at I1 who is at a distance of V1.
CI1= P1I1 = V1 (as the lens is thin)
CC1 = P1C1 = R1
CO = P1O = u
It follows from the refraction due to convex spherical surface XP1Y

The refracted ray from A suffers a second refraction on the surface XP2Y and emerges along BI. Therefore I is the final real image of O.
Here the object distance is

(Note P1P2 is very small)

(Final image distance)
Let R2 be radius of curvature of second surface of the lens.
\ It follows from refraction due to concave spherical surface from denser to rarer medium that

All the best.
Win exciting gifts by                                                              answering   the           questions    on            Discussion        Forum.    So           help                 discuss         any                query     on             askiitians       forum    and         become  an         Elite                 Expert       League                askiitian.

Sagar Singh
B.Tech, IIT Delhi
sagarsingh24.iitd@gmail.com

```
6 years ago
Think You Can Provide A Better Answer ?

## Other Related Questions on General Physics

View all Questions »
• Complete JEE Main/Advanced Course and Test Series
• OFFERED PRICE: Rs. 15,900
• View Details
Get extra Rs. 1,272 off
USE CODE: Neerajwin
• Kinematics & Rotational Motion
• OFFERED PRICE: Rs. 636
• View Details
Get extra Rs. 51 off
USE CODE: Neerajwin