How is the physical
change in the robot reversible,
and how can you tell that the
change follows the law of
conservation of mass?
need the answer ASAP

What is the scientific definition of energy that relates to work

Modern physics a photon emitted from an excited hydrogen atom has an energy of 3.02 electron volts. which electron energy-level transition would produce this photon? a. n=1 to n=6 b. n=2 to n=6 c. n=6 to n=1 d. n=6 to n=2 i chose b but the correct answer is d can someone tell me why? and what's the difference?

What are similarities and differences of reflection, refraction, diffraction and absorption?