ism_ch25

ism_ch25 - Chapter 25 Electromagnetic Waves Answers to...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 25 Electromagnetic Waves Answers to Even-numbered Conceptual Questions 2. The electric and magnetic fields in an electromagnetic wave are proportional to one another, as we see in Equation 25-9. Therefore, doubling E results in a doubling of B . The intensity of such a wave depends on the square of the fields, however, as Equation 25-10 shows. It follows that the intensity of an electromagnetic field is quadrupled if its electric field is doubled. 4. We can tell if a weather system is approaching or receding by noting if the frequency of the reflected radar beam has been shifted up or down. The system is approaching if the frequency is higher; it is receding if the frequency is lower. 6. We note from Equation 25-12 that the radiation pressure depends on the intensity of a wave. The intensity, in turn, depends on the square of the fields, as Equation 25-10 shows. Therefore, the electric field in beam 2 has a magnitude given by 2 E 0 . 8. Ideally, the sails should be reflecting. Recall that there is a greater transfer of momentum when a beam is reflected than when it is merely absorbed. 10. If the incident light is unpolarized, the transmitted intensity is the same in both cases. Specifically, the first filter in both cases reduces the intensity of unpolarized light by a factor of 2. It also leaves the light polarized in the direction of its transmission axis, which is at an angle θ relative to the transmission axis of the second filter. The second filter then reduces the transmitted intensity by a further factor of cos ( ) 2 . 12. Light reflected from a horizontal surface has a polarization in the horizontal direction. It follows that when you sit upright, with the transmission axis of your glasses in the vertical direction, they will block most of the reflected light. When you lie on your side, however, the transmission axis is horizontal. This allows most of the reflected light to enter your eyes. 14. View the light reflected from a horizontal surface, such as a tabletop. This light is polarized primarily in the horizontal direction. Therefore, if you rotate the sheet of polarizing material until you receive a maximum amount of reflected light, you will know that its transmission axis is horizontal. 16. The light from the sky is polarized at right angles to the direction of the Sun; therefore, the amount of light received by each of the two polarizing eyes will depend on the orientation of the spider relative to the Sun. By monitoring the amount of light received by each eye, the spider can maintain a course on a given heading relative to the Sun. 18. As mentioned in the answer to Question 14, the light reflected from a horizontal surface is polarized primarily in the horizontal direction. If the glasses are merely tinted, reflected light will have the same intensity no matter how the glasses are rotated. If they are Polaroid, however, you will notice a striking difference in reflected intensity as you rotate the glasses.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 19

ism_ch25 - Chapter 25 Electromagnetic Waves Answers to...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online