Can more than two waves can interfere in a given medium

If two parallel light rays hit a mirror, they will not be parallel to each other after they reflect.

First answer marked as brainiest which is the correct equation describing the first law of thermodynamics? a) when the internal energy of a system changes, it equals the amount of heat added plus the work done. b) when work is done by the piston, it is equal to the heat added plus the change in internal energy of the system. c) when heat is added to the system, it is equal to the amount of work done by the piston plus the change in internal energy of the system.

Meaning of a nonzero y-intercept to a graph of reaction distance versus speed