system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:When does light stop?

Today i was walking along a lake on a beautiful sunny day.  I noticed the reflection of the mountains off the lake.  I realized that what i am seeing are photons bounced off the lake, but then i realized they were 1st bounced off the mountain, and they came from the sun. 

  When does the photon stop?
gpt
Whenever light hits something, some of it is absorbed and gets converted into another form of energy (heat), while some of it is reflected. When you the light hits your eyes, it is absorbed by your retina.