Or if you need RF communication, use 433mhz RF transmitter/receiver modules.
http://www.instructables.com/id/RF-315433-MHz-Transmitter-receiver-Module-and-Ardu/
In your case there is no need for a microcontroller. Give logic high voltage on the data input pin of transciever and on the receiver the data output pin will become high. Connect your light source to the data output pin of receiver using a transistor switch.