Conceptual Questions

ssm Solution is in the Student Solutions Manual

| 1 | Which of the following concepts applies to both sound waves and electromagnetic waves: (a) intensity or (b) polarization? Account for your answer.

| 2 | Refer to Figure 24-2. Between the times indicated in parts c and d in the drawing, what is the direction of the magnetic field at the point P for the electromagnetic wave being generated? Is it directed into or out of the plane of the paper? Justify your answer.

| 3 | ssm A transmitting antenna is located at the origin of an x, y, z axis system and broadcasts an electromagnetic wave whose electric field oscillates along the y axis. The wave travels along the axis. Three possible wire loops are available for use with an LC-tuned circuit to detect this wave: One loop lies in the xy plane, another in the xz plane, and the third in the yz plane. Which of the loops will detect the wave? Why?

| 4 | Why does the peak value of the emf induced in a loop antenna (see Figure 24-6) depend on the frequency of the electromagnetic wave, whereas the peak value of the emf induced in a straight-wire antenna (see Figure 24-5) does not?

| 5 | Suppose that the electric field of an electromagnetic wave decreases in magnitude. Does the magnetic field increase, decrease, or remain the same? Account for your answer.

| 6 | ssm An astronomer measures the Doppler change in frequency for the light reaching the earth from a distant star. From this measurement, can the astronomer tell whether the star is moving away from the earth or whether the earth is moving away from the star? Explain.

| 7 | Is there any real difference between a polarizer and an analyzer? In other words, can a polarizer be used as an analyzer, and vice versa?

| 8 | Malus’ law applies to the setup in Figure 24-21, which shows the analyzer rotated through an angle and the polarizer held fixed. Does Malus’ law apply when the analyzer is held fixed and the polarizer is rotated? Give your reasoning.

| 9 | In Example 7, we saw that when the angle between the polarizer and analyzer is , the intensity of the transmitted light drops to one-tenth of that of the incident unpolarized light. What happens to the light intensity that is not transmitted?

| 10 | Light is incident from the left on two pieces of polarizing material, 1 and 2. As part a of the drawing illustrates, the transmission axis of material 1 is along the vertical direction, and that of material 2 makes an angle of with respect to the vertical. In part b of the drawing the two polarizing materials are interchanged. (a) Assume that the incident light is unpolarized and determine whether the intensity of the transmitted light in drawing a is greater than, equal to, or less than that in drawing b. (b) Repeat part (a), assuming that the incident light is linearly polarized along the vertical direction. Justify your answers to both parts (a) and (b).

| 11 | ssm You are sitting upright on the beach near a lake on a sunny day, wearing Polaroid sunglasses. When you lie down on your side, facing the lake, the sunglasses don’t work as well as they did while you were sitting upright. Why not?

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