Relationship between OD600 and bacterial number - (Sep/11/2012 )

Hi, everyone!
I have a question about OD600 and bacterial number. Is there a linear relationship exists between OD600 and bacteria concentration for a certain bacteria strain? For example, if the OD600 of my culture increases from OD600~0.6 to 1.2, will the bacteria number doubles as well?

Thank you! I am looking forward for your reply.

See post here