- #1

CaptainEvil

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## Homework Statement

If a quasar varies on a time scale of four months, how does the maximum size of the emitting region compare with the Schwarzschild radius for a 10

^{9}MSun black hole?

## Homework Equations

## The Attempt at a Solution

Calculating the S radius of the black hole is trivial, but I think I missed the lecture on varying quasars. I don't know of any equations for 'emitting regions' let alone how to use its rotation period to do so. Can anyone start me off on the right track?

fwiw I calculated the S radius by the eqn 3km(M/Msun) = 3 x10

^{12}m