Question

What is meant by phase, amplitude and frequency?

Answer 1

Phase in the above diagram is 0 degrees since a sine wave at 0 degrees has a value of 0 which is the case in the above diagram. If the phase had been 90 degrees, the wave would be shifted in such a manner so that the value of the wave at 0 degrees would have been equal to its amplitude.
Amplitude is the maximum distance the wave travels from its mean position as is shown in the diagram (marked as A).
Frequency on the other hand is equal to the reciprocal of the Time period. In other words, it equals the number of waves that passes a given point per second.