Beginning of Essay
Many scientific applications have made great use of the wave nature of light. Until the first half of the century the nature of light remained completely a mystery. Some thought light to be a particle while others believed it to be a wave. Scientists now know ....

Middle of Essay
.... relation x = Acos(wt + f) where x is the position along the x axis A is the amplitude or in other words the maximum possible displacement w is the angular frequency and f is the phase constant or phase angle and has units of radians per second. The phase constant determines the position of the particle at time t = 0. The quantity (wt+ f) is called the phase. The above function x repeats itself whenever wt = n2p where n is an integer. The period T of the motion is the time it takes for the motion to complete one revolution or cycle. The unit for the period T is seconds. Since the function repeats itself every period T for any time t and i ....