An object is placed in front of convex lens made of glass. How does the image distance vary if the refractive index of the medium is increased in such a way that still it remains less than the glass?

I tried to use lens maker's formula. As per me, image distance should increase. Can anyone confirm?

1 Answer
Mar 11, 2016

The image distance will be increased

Explanation:

We are to use here the Lens maker's for as stated below

1f=(μ2μ11)(1r11r2)

Where f =focal lens of the lens
μ1=refractive index of the surrounding medium
μ2=refractive index of medium of the lens
r1= radius of curvature of the lens of first refracting surface where the beam is incident.
r2= radius of curvature of the lens of the second refracting surface through which emergent beam comes out.

Here r1and r2 remaining same and normally μ2>μ1

If the refractive index of surrounding medium i.e. μ1 is increased but kept less than μ2 then the ratio μ2μ1 will be diminished and as a result the focal length f will be increased.
we know
1v1u=1f
where v = image distance
u = object distance
object distance remaining same the image distance proportionately increases with the increase in focal length.