IIT JEE , AIEEE Forum - Physics , Optics

jjthomson

Why convex lens has converging nature?

pottermania1990

why is water colourless?????????

nitigya

1/f = 2(u₂- u₁)/r for convex lense if placed in a homogeneous medium and has same radius for the curved part. (u2= refrtive index of the lense)

so if lense is placed in medium denser than the lense. focal length will decrease.

iby chosing apropriate u1 we can make a convex lense diverging

the convex lens has converging nature in air as air is less dense than material of the lense and focal length always coming positive and will be converging

corect me if iam wrong or else rate me

aditya_arora04

Hi,

nitigya, yr concept is right, but not the accurate explanation.

Look,

Convex lens is converging under certain conditions because :

when light strikes the first surface, then light goes from rarer to denser medium and hence goes towards normal. At the other end, it goes refraction away from the normal. So, at the end, it acts as a converging lens.

But yes, under certain conditions it may act as diverging lens.

spideyunlimited

Because of the nature of the path the light ray has to undergo at different distances of striking from the optical centre.. longer path in the centre (as it is thicker in the centre) and lesser path to cover at the edges (as it is thinner at the ends)

aaplahs

because in accordance to Huygen's Principle the incident plane wavefront results in a converging wavefront.

akhil_o

Assume the lens 2 b made up of many sections...as in figure.You'll automticaly see why

Not the best method and not the exact reason but easier 2 understand

ramyani

yes,

akhil_o (83) is right.

hardcore_genius

Yes, the prism explanation is right & straight forward.

dinesh_ddt

akhil coooll...! take a rate.

kanka0901

The inside of a convex lens can be considered as a number of prisms.The prisms are faced upwards above the principal focus and the prisms are faced downwards below the principal focus.So,when the light ray is incident on the prisms,they bend towards the base and produces a converging beam of rays.So convex lens has converging nature.

harsh15

Consider a plane wavefront incident on a convex lens.Different portions of the wavefront have to travel differetn thickness of the lens before emerging out ,being maximum at the center and minimum at the edges .As light travels slower in lens material than in air therefore refracted wavefront is converging spherical wavefront as shown:-

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