Hmm What type of wave is a radio wave? Is that type in the answers? Let s see We have distance We want time

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1 Quest Chapter 27 # Question Hints 1 At what speed does the radio wave travel? 1. slower than the sound 2. More information is needed. 3. at the speed of sound 4. faster than visible light 5. at a speed between the speed of light and the speed of sound 6. at the speed of light 2 Radio and TV transmissions are being emitted into space, so Star Trek episodes are streaming out into the universe. The nearest star is m meters away. If civilized life exists on a planet near this star, how long will they have to wait for the next episode? Answer in units of years. Hmm What type of wave is a radio wave? Is that type in the answers? Let s see We have distance We want time What equation has both distance and time in it? 3 From the stands of a race track why do you notice smoke from the starter s gun before you hear it fire? 1. Light travels about a million times faster than sound in air. 2. Smoke spreads out quickly. 3. The gun smokes before making sound. 4. The response time of eyes is shorter than that of ears. 5. Sound has a much longer wavelength than Do we have the rest of the information to solve the problem? Two things happen at the same time at some location far away. You experience two waves from that event at different times. Why would that be?

2 4 How is the wavelength of light related to its frequency? 1. Waves of high frequency have long wavelengths. 2. For visible light wavelength has an inverse relationship with frequency; for invisible light, it has a direct relationship. 3. There is no relationship between frequency and wavelengths at all. 4. Waves of low frequency have long wavelengths. 5. Sometimes waves of low frequency have long wavelengths; sometimes waves of high frequency have long wavelengths. 5 (part 1 of 2) If the frequency of the wave used by your favorite station is 96 Megahertz, what is the wavelength? Answer in units of m. 6 (part 2 of 2) If the station is 50 km away, how long does it take for the radio waves to reach you from the station? Answer in units of seconds. 7 In what way do sound waves differ from radio waves? 1. Sound waves travel faster than radio waves. 2. Sound waves require a medium to travel and radio waves do not. 3. Radio waves require a medium to travel and sound waves do not. 8 If someone asked you to prove that electromagnetic waves travel in a vacuum, what would you say? 1. We can see polarized 2. We see stars and planets in the sky. 3. We can see refracted 4. We can see diffracted Do we have an equation that relates wavelength and frequency? What was that equation that relates wavelength and frequency? You want time. You have distance in km. What do you need to find the time? What type of wave is a radio wave? Think!

3 9 Comparing microwaves and visible light, which of the following is true? 1. Microwaves have lower frequency, slower speed, and longer wavelength than visible 2. Microwaves have lower frequency, faster speed, and shorter wavelength than visible 3. Microwaves have lower frequency, same speed, and longer wavelength than visible 4. Microwaves have higher frequency, same speed, and longer wavelength than visible 10 What is the difference between gamma rays and infrared rays? 1. Gamma rays have a lower frequency and longer wavelength. 2. Gamma rays have a higher frequency and shorter wavelength. 3. Gamma rays have a higher frequency and longer wavelength. 4. Gamma rays have a lower frequency and shorter wavelength. 11 What has the longest wavelength? 1. X rays 2. gama rays 3. ultraviolet light waves 4. light waves 5. radio waves 12 What has the highest frequency? 1. X ray 2. radio wave 3. infrared light 4. visible light 5. gamma ray 6. ultraviolet light Check your notes. We talked about this. Read carefully. Cross out obviously wrong answers. Same hint as for number 9. Same hint. Same hint.

4 13 What is the principal difference between a radio wave and visible light? 1. Radio waves have lower frequencies than visible light waves. 2. Light is more powerful than radio waves. 3. They travel at different speeds. 4. Radio waves are not electromagnetic waves. 5. Radio waves are sound waves. 14 What color does visible light of the lowest frequency appear? Of the highest? 1. green for lowest; red for highest 2. yellow for lowest; green for highest 3. red for lowest; violet for highest 4. red for lowest; blue for highest 5. blue for lowest; green for highest 6. violet for lowest; red for highest 15 If a bell rings inside a bell jar, we can no longer hear it when the air is pumped out, but we can still see it. What differences in the properties of sound and light does this indicate? 1. The bell jar is a good absorber of sound. 2. There is a frequency shift of sound waves when it passes through a vacuum. 3. Light needs a material medium for its transmission, while sound does not. 4. Sound needs a material medium for its transmission, while light does not. 5. The bell jar is a good light transmitter. 16 What two physics mistakes occur in a science fiction movie that shows a distant explosion in outer space, where you see and hear the explosion at the same time? 1. The explosion cannot occur in outer space; if it could, the sound would reach you before the 2. None of these 3. In outer space there is no material to carry light; if there were, the sound would reach you before the 4. The explosion cannot occur in outer space; if it could, the faster-moving light would reach you before the sound. 5. In outer space there is no air to carry sound; if there were, the faster-moving light would reach you before the sound. Same hint. Check your notes or check page 408. What is needed for light to propagate? What is needed for sound to propagate? What are the differences? Think: 2 mistakes involving outer SPACE and seeing and hearing at the SAME TIME

5 17 How does the average speed of light in glass compare with its speed in a vacuum? 1. The speed of light in glass is higher. 2. For colorless glass, the light speed is higher than in a vacuum; for colored glass, the light speed is lower than in vacuum. 3. The speed of light in glass is lower. 4. There is no difference between the speed of light in glass and in a vacuum. 5. It cannot be judged because we don t know what kind of glass it is. 18 Is glass opaque to light of frequencies that match its own natural frequencies? 1. Yes; the electrons in the glass will be excited by the incident light, the frequecies of which match the natural frequencies of the glass. 2. No; the frequencies of glass are in magnitudes that no light frequencies will match. 3. Yes; the energy of light will be totally converted into the energy of electrons in the glass when the frequencies of light match the natural frequencies of the glass. 4. No; the frequencies of glass are related to the movements of glass atoms, which are almost not affected by the frequencies of 5. More information is needed. 19 The mechanical advantage of a machine is the number of times it 1. multiplies the resistance force. 2. multiplies the effort force. correct 3. changes the direction of the effort force. 4. changes the direction of the resistance force. 20 (part 1 of 2) If a golf ball and a ping-pong ball both move with the same kinetic energy, which has the greater speed? 1. the golf ball 2. The two balls have the same speed. 3. Cannot be determined 4. the ping-pong ball What happens to its speed when a wave changes medium? Page 410 See page 112. KE depends on what? (KE = ½ mv 2 ) What do you know about the mass of each ball?

6 21 (part 2 of 2) In a gaseous mixture of massive molecules and light molecules with the same average KE, which have the greater speed? 1. Cannot be determined 2. the light molecules correct 3. the massive molecules 4. They have the same speed. 22 Power equals work 1. divided by time. 2. divided by weight. 3. times distance. 4. divided by distance. Same hint as #20 except that instead of golf and ping-pong balls you have molecules. Look up the definition of power. 23 An object moves along a circular path with a constant speed, ~vo. The average acceleration in going from A to B is 1. west 2. zero 3. none of the others 4. east 5. south 6. north 24 (part 1 of 5) A wheel makes 28 revolutions in 4 seconds. What is the angular velocity of the wheel? Answer in units of cycles/s 25 (part 2 of 5) What is the angular velocity of the wheel in deg/s? Answer in units of deg/s 26 (part 3 of 5) What is the angular velocity of the wheel in rad/s? Answer in units of rad/s 27 (part 4 of 5) What angular displacement occurs if the wheel spins for 37 s? Answer in units of deg 28 (part 5 of 5) What angular displacement occurs if the wheel spins for 39 s? Answer in units of rad Check the diagram. They want the AVERAGE direction. A revolution is how many cycles?... A revolution is how many degrees?... A revolution is how many radians?... Use your answer from #25. Use your answer from #26.

7 29 Suppose a ping-pong ball and a bowling ball are rolling toward you with the same momentum, and you exert the same average force in stopping each of them. Which ball can be stopped in the least time? 1. Both will come to rest in the same time. 2. The much more massive bowling ball takes much longer to stop; the ping-pong ball stops almost instantly. 3. More information is needed the two masses. 4. The ping-pong ball takes much longer to stop because it has so much momentum compared to normal; the bowling ball stops fairly quickly. A moving object takes time to stop. During that time, what has to be removed from the object? See page 87 in the text.