What name is given to sections of longitudinal waves where the medium is 'stretched out'?

8. why do radio telescopes convert radio waves (analog signals) to electrical (digital) signals for analysis? (hint: what did the article say about the advantages of digital signals? )

Name three different units of energy used to measure heat and describe what type of situations each is usually used.

Explain why electric current cannot exist if a current doesn't have a voltage source.