Which of the following is for forbidden based on the second law of thermodynamics? A) Heat flowing from hot to cold
B) A machine that is 100% efficient
C) Energy being wasted when heat is converted into mechanical energy
D) Heat flowing from hot to cold

B) A machine that is 100% efficient

Explanation:

The second law of thermodynamics states that a machine will always be less than 100% efficient as heat is never converted completely into mechanical energy.  Even an ideal, frictionless engine can't convert anywhere near 100% of its input heat into work.

Second law of thermodynamics states that any natural system tends to disorder. That is, the total entropy of the universe will tend to increase over time.  Heat will alwyas from a hotter body to a colder body.

When a ray of light is directed into a mirror , REFRACTION takes place . the light either bends towards the normal or it bends away from the normal depending on from which medium the light passes to which medium .