What is the speed of light in a vacuum? What would happen to this speed as it enters a different medium?
Help me please

Light travels faster in a vacuum than it does in any other medium. Light changes speed as it passes from one medium to another. This is called refraction. The frequency of light does not change as it refracts.

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.