What's the difference between direct and circumstantial

Direct evidence is evidence which a person actually observes. Circumstantial evidence is evidence that was not observed but from which a judge or jury could infer that an incident occurred. The most common example in a criminal trial of circumstantial evidence is footprints in the snow.

1 - wave length

2 - amplitude

3 - crest

4 - trough

explanation:

duh.