# Q 2.31: The farthest objects in our Universe discovered by modern astronomers are so distant that light emitted by them takes billions of years to reach the Earth. These objects (known as quasars) have many puzzling features, which have not yet been satisfactorily explained. What is the distance in km of a quasar from which light takes 3.0 billion years to reach us?

Let the distance of a quasar from Earth be D km.

We know , Speed of light = $3\times10^8 ms^{-1}$

And, time taken by light to reach us , t = 3.0 billion years = $3\times 10^{9} years = 3\times 10^{9} \times365\times24\times60\times60 \ s$

$\therefore$ D =Speed of Light x t

= $(3 \times 10^8 ms^{-1}) \times(3\times 10^{9} \times365\times24\times60\times60 \ s)$

= $2.8\times 10^{22}\ m$

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