AirDrop between iPhone 6 & iMac (late 2009 Model)

I am a new iPhone user and recently bought an iPhone 6. I tried using AirDrop to transfer files between my phone and iMac, but this does not work. I visited the local Mac store and was able use AirDrop between my iPhone and the latest iMac to transfer files. However I cannot do this on my iMac. My phone does not display in the home page window of AirDrop and my phone is set for AirDrop to Everyone. Any assistance to set this up will be appreciated.