Three Laws of Thermodynamics

An easy and funny way to define the three laws of thermodynamics (by C.P. Snow, a British scientist and author):

1. you cannot win (you can’t get something for nothing because matter and energy are conserved. 
2. You cannot break even (you cannot return to the same energy state because entropy always increases
3. You cannot get out of the game (because absolute zero is not attainable).

From http://www.physicsplanet.com/articles/three-laws-of-thermodynamics

Wave Interference

Wave interference is the result of two or more waves meeting each other at one point and one time. As a result, one resultant wave is formed having the amplitude of the sum of all wave amplitudes interfering at this particular point. This is called the principle of superposition.

Constructive and Destructive interferences:
Basically, when the direction of waves are the same, the amplitude of the resultant wave will increase or build up because we're adding the amplitude of these waves. This is called Constructive interference.
Vice, versa, when the direction of waves are not the same, the amplitude of the resultant wave will be depended on the amplitude of these waves in different directions because they'll in some extent, cancels out each other's energy. This is called Destructive interference.

Here is an example illustrating both interferences:

Now, as to exactly how to draw the resultant wave, it also bothers me foir the fact that it's hard to imagine what the resultant wave will look like.There are multiple ways of how one can approach the question. For me,I would pick the method of finding the resultant amplitude at each point where more than two waves interfere with one another. At places where waves do not interfere with each other, the shape is then same as before, when they do interfere, simply find the resultant amplitude and keep note by drawing a note. Continue solving the problem in this matter from one end to the other. Once, no more interferences are left, we can simply connect the dots to produce the resultant wave.