This happens when Ruby becomes disappointed with Tom when the hose leaks and Ruby can no longer dive. The two stop hanging out, and Tom loses her friendship.
The light, then, is the light that her friendship brought to his life. Her friendship is light -- it is happiness and is joy to Tom. When the two friends stop hanging out, the light goes out of the marsh. The author is saying the joy has gone out of Tom's life.
Im in math class right now what subjcet is this
An adjective is a word that describes, such as "She was a beautiful woman". The adjective in this sentence is beautiful because if describes the woman. Hope this helps!