I have 4.8V 0.5A Light Bulb and want to use RPI's GPIO pins to power it. How can I do that?
This is an excellent question as a lot of people want to drive loads using their Raspberry Pi. I'm not sure why you received a -1 your question may have need rephrasing.
The MOSFET in the schematic above is a general purpose one. You will have to choose a Logic Level MOSFET that will work with 3.3V on the gate.
You can add isolation using an optocoupler as well if you want higher isolation between the power rails.