If two sine waves of the same frequency have a phase difference of JT radians, then

Both will reach their minimum values at the same instant
Both will reach their maximum values at the same instant
When one wave reaches its maxi¬mum value, the other will reach its minimum value
None of the above

The correct answer is: C. When one wave reaches its maximum value, the other will reach its minimum value.

A sine wave is a periodic function of time that repeats its values over and over again. The frequency of a sine wave is the number of times it repeats its values in one second. The phase of a sine wave is the position of the wave relative to its starting point.

Two sine waves of the same frequency have a phase difference of $\pi$ radians if they are out of phase by one-half cycle. This means that when one wave reaches its maximum value, the other wave will reach its minimum value.

Here is a diagram of two sine waves with a phase difference of $\pi$ radians:

[asy]
unitsize(1 cm);

draw((0,-1.2)–(0,1.2));
draw((0,0)–(4*pi,0));

real g(real t) {
return sin(t);
}

real h(real t) {
return -sin(t + pi);
}

draw(graph(g,0,4pi),red);
draw(graph(h,0,4
pi),blue);

label(“$y = g(t)$”, (2pi,1), E);
label(“$y = h(t)$”, (2
pi,-1), E);
[/asy]

As you can see, the two waves are out of phase by one-half cycle. When one wave reaches its maximum value, the other wave reaches its minimum value.