What adapter I need to connect imac to TV?

That imac has a Mini DisplayPort for audio/video output. You need a mini-DP to HDMI converter such as this one to run it to your Sony: a href="http://store.apple.com/us/product/H1824ZM/A?fnode=MTY1NDA3Ng&mco=MTgwOTAzMjI" rel="nofollow"http://store.apple.com/us/product/H1824Z…/a