I am making a project in which me and my classmates are going to find the relationship between speed of motor and rpm. For this project we are using Arduino and laser as the detector . So does Arduino provide a laser detector module?
A simple LDR( light dependent resistor ) will do the trick.
Laser Setup and Detection
Also it can help to put the LDR inside of a tube to reduce interference from other light sources.
A LDR may be too slow, photo diodes or transistors are much faster. See (rotary) encoders, light barriers.
I don't understand the "relationship" between speed and rpm - both are proportional.