DATA Because the speed of light in vacuum (or air) has such a large value, it is ver...

DATA Because the speed of light in vacuum (or air) has such a large value, it is very difficult to measure directly. To measure this speed, you conduct an experiment in which you measure the amplitude of the electric field in a laser beam as you change the intensity of the beam. Figure P32.49 is a graph of the intensity I that you measured versus the square of the amplitude E_max of the electric field. The best-fit straight line for your data has a slope of 1.33 × 10^-3 J/(V² ⋅ s). (a) Explain why the data points plotted this way lie close to a straight line. (b) Use this graph to calculate the speed of light in air.