JEE Advanced 2020 Paper 1

A circular disc of radius R carries surface charge density σ(r)=σ0(1−

r

R

), where σ0 is a constantand r is the distance from the center of the disc. Electric flux through a large spherical surface thatencloses the charged disc completely is ϕ0. Electric flux through another spherical surface of radius

R

4

and concentric with the disc is ϕ. Then the ratio

ϕ0

ϕ

is _______