What sensors shall be used to detect if a dustbin is full (light weight material like paper,hair, etc)?
You can always use IR sensor. But they need to be cleaned. Rather if you want you can use ultrasonic distance measurement sensors. This way you can calculate the height of the trash in the bin when placed under the sensor. And you don't need to clean the sensor. Another advantage will be that no matter what container you use, the system can be used. This saves your thought on mounting the sensor inside or along with the bin and the bin remains replaceable. Programming and getting results from the sensor however depend on the thoughtfulness of the programmer.