A surface wave is a wave in which particles of the medium undergo a circular motion.
To calculate instantaneous speed, we need to divide part of the total distance traveled by time. However, we don't want to use the distance of the entire trip, because that will give us average speed.
Answer:
2: Condensation. 4: 1,d; 2,c; 3,a; 4,e;5,b.
Explanation:
The velocity of the particle is given by the derivative of the position vector:

(a) The particle is moving in the <em>x</em>-direction when the <em>y</em>-component of velocity is zero:

But we want <em>t</em> > 0, so this never happens, unless 2<em>c</em> = <em>d</em> is given, in which case the <em>y</em>-component is always zero.
(b) Similarly, the particle moves in the <em>y</em>-direction when the <em>x</em>-component vanishes:

We drop the zero solution, and we're left with

In the case of 2<em>c</em> = d, this times reduces to <em>t</em> = <em>c</em>/(6<em>c</em>) = 1/6.
OPTION D is the correct answer.
Refer to the attachment for complete calculation...