The farthest objects in out universe discovered by modern astronomeres are so distant that light emitted by them takes billions of year to reach the earth. These object (known as quasers) have may puzzling features, which have yet not been satisfactorily explained. What is the distance in km of a quasar form which light takes 3.0 billion years to reach us?

Explanation

The time taken by light from the quasar to the observer
`t = 3.0` billion yesrs `=3.0 xx 10^(9)` years As `1 ly =9.46xx10^(15) m`
`:.` Distance of quasar from the observer `d = 3.0xx10^(9) xx9.46xx10^(15) m`
`=28.38xx10^(24)m=2.8xx10^(25)m` or `2.8xx10^(22) km`.