Final answer:
The observed frequency does not become infinite when the source moves at the speed of sound (false), and dropping a bar magnet through a copper tube induces an electric current (true), demonstrating Doppler Effect and electromagnetic induction respectively. So, the correct answer is a) True.
Step-by-step explanation:
Understanding Doppler Effect and Electromagnetic Induction
When addressing the first question about the observed frequency becoming infinite, it is necessary to understand the principles of the Doppler Effect.
The observed frequency does not become infinite when the source is moving at the speed of sound.
Therefore, the correct answer is:a. False
Regarding the second question about dropping a bar magnet through a copper tube, this is a classical example of electromagnetic induction.
A magnetic field changing with time, such as a bar magnet falling through a copper tube, induces an electric current in the tube due to Lenz's Law.
Thus, the correct answer is: b. True.