7.
What is meant by independent
Independent behaviour of waves?

Its AnsweredHere it is

A wave  preserve its individuality while travelling through space.So when a Number of waves travel through a region at same time, each wave travels independently of the others i.e., as if all other waves were absent. That is why, with so many different musical instrument playing simultaneously in a full orchestra , we can still identify the note produced by an individual instrument. An important consequence of the independent behaviour of the Waves is the principle of superposition of waves.

Explanation:

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.