The intensity of electromagnetic waves from the sun is1.4 kW/m2 just above the earth's

a. In your own words, define what a transverse wave is. b. Give an example of a wave that, from your own experience, you know is a transverse wave. What obse rvations or evidence tells you this is a transverse wave?

a. In your own words, define what a longitudinal wave is. b. Give an example of a wave that, from your own experience, you know is a longitudinal wave. What observations or evidence tells you this is a longitudinal wave?

The wave pulses shown in Figure Ql5.3 travel along the same string. Rank in order, from largest to smallest, their wave speeds VJ> v2, and v3. Explain.

Is it ever possible for one sound wave in air to overtake and pass another? Explain.

A wave pulse travels along a string at a speed of 200 emfs. What will be the speed if: a. The string's tension is doubled? b. The string's mass is quadrupled (but its length is unchanged)? c. The string's length is quadrupled (but its mass is unchanged)? d. The string's mass and length are both quadrupled? Note that parts a-d are independent and refer to changes made to the original string.

Harbor seals, like many animals, determine the direction from which a sound is coming by sensing the di fference in arrival times at their two ears. A small difference in arrival times means that the object is in front of the seal; a larger difference means it is to the left or right. There is a minimum time difference that a seal can sense, and this leads to a limitation on a seal's direction sense. Seals can distinguish between two sounds that come from directions 3 apait in air, but this increases to 9 in water. Explain why you would expect a seal's directi onal discrimination to be worse in water than in air.

A thermostat on the wall of your house keeps track of the air temperature. This simple approach is of little use in the large volume of a covered sports stadium, but there are systems that determine an average temperature of the air in a stadium by measuring the time delay between the emission of a pulse of sound on one side of the stadium and its detection on the other. Explain how such a system works.

When water freezes, the density decreases and the bonds between molecules become stronger. Do you expect the speed of sound to be greater in liquid water or in water ice?

Figure QJS.9 shows a historygraph of the motion of one point on a string as a wave traveling to the left passes by. Sketch a snapshot graph for this wave.

Figure Q 15. l 0 shows a hi story graph and a snapshot graph for a wave pulse on a string. They describe the same wave from two perspectives. a. In which direction is the wave traveling? Explain. b. What is the speed of this wave?

Rank in order, from largest to smallest, the wavelengths A1 to A3 for sound waves having frequencies f 1 = I 00 Hz, Ji = I 000 Hz, and h = 10,000 Hz. Explain

Bottlenose dolphins useecholocation pulses with a frequency of about I 00 kHz, higher than the frequencies used by most bats. Why might you expect these water-dwell ing creatures to use higher echolocation frequencies than bats?

Some bat species have auditory systems that work best over a narrow range of frequencies. To account for this, the bats adjust the sound frequencies they emit so that the returning, Dopplershifted sound pulse is in the correct frequency range. As a bat increases its forward speed, should it increase or decrease the frequency of the emitted pulses to compensate?

A laser beam has intensity 10 . a. What is the intensity, in terms of 10, if a lens focuses the laser beam to 1110 its initial diameter? b. What is the intensity, in terms of 10 , if a lens defocuses the laser beam to I 0 times its initial diameter?

When you want to "snap" a towel, the best way to wrap the towel is so that the end that you hold and shake is thick, and the far end is thin. When you shake the thick end, a wave travels down the towel. How does wrapping the towel in a tapered shape help make for a good snap? Hint: Think about the speed of the wave as it moves down the towel.

The volume control on a stereo is designed so that three clicks of the dial increase the output by IO dB. How many clicks are required to increase the power output of the loudspeakers by a factor of 100?

A bullet can travel at a speed of over I 000 mis. When a bullet is fired from a rifle, the actual firing makes a distinctive sound, but people at a distance may hear a second, different sound that is even louder. Explain the source of this sound.

You are standing at x = 0 m, listening to seven identical sound sources described by Figure Q 15. 18. At t = 0 s, all seven are at x = 343 m and moving as shown below. The sound from all seven will reach your ear at 1 = 1 s. Rank in order, from highest to lowest, the seven frequencies / 1 to h that you hear at 1 = 1 s. Explain.

Police radar guns wor.k by measuring the change in frequency of a reflected pulse of electromagnetic waves. A gun reads correctly only if a car is moving directly toward or away from the person making the measurement. Explain why this is so.

Denver, Colorado, has an oldies station that calls itself "KOOL I 05." This means that they broadcast radio waves at a frequency of 105 MHz. Suppose that they decide to describe their station by its wavelength (in meters), in stead of by its frequency. What name would they now use? A. KOOL 0.35 B. KOOL 2.85 C. KOOL 3.5 D. KOOL 285

"What is the frequency of blue light with a wavelength of 400 nm? A. l.33X J03Hz B. 7.50 X 10 12 Hz C. 1.33 X 1014 Hz D. 7.50 x 10 14 Hz"

Ultrasound can be used to deliver energy to tissues for ther- apy. It can penetrate tissue to a depth approximately 200 times its wavelength. What is the approximate depth of penetration of ultrasound at a frequency of 5.0 MHz? A. 0.29 mm B. 1.4 cm C. 6.2 cm D. 17cm

A sinusoidal wave traveling on a string has a period of 0.20 s, a wavelength of 32 cm, and an amplitude of 3 cm. The speed of this wave is A. 0.60cm/s. B. 6.4 cm/s. C. 15 cm/s. D. 160cm/s.

Two strings of different linear density are joined together and pulled taut. A sinusoidal wave on these sttings is traveling to the right, as shown in Figure Q l5.24. When the wave String 2 goes across the boundary from string I to string 2, the frequency is unchanged. What happens to the velocity? A. The velocity increases. B. The velocity stays the same. C. The velocity decreases.

You stand at x = 0 m, listening to a sound that is emitted at frequency 'f~. Figure Q l5.25 shows the {requency you hear J; during a four-second interval. Which of the following describes the motion of the sound source? A. lt moves from left to right FIGURE 015.25 and passes you at t = 2 s. B. It moves from right to left and passes you at t = 2 s. C. It moves toward you but doesn't reach you. It then reverses direction at t = 2 s. D. Tt moves away from you until t = 2 s. Tt then reverses direction and moves toward you but doesn 't reach you.

Research vessels at sea can create images of their surroundings by sending out sound waves and measuring the time until they detect echoes. This image of a shipwreck on the ocean bottom was made from the surface with 600 kHz ultrasound. a. What was the wavelength? b. How deep is the shipwreck if echoes were detected 0.42 s after the sound waves were emitted?

a. Telephone signals are often transmitted over long distances by microwaves. What is the frequency of microwave radiation with a wavelength of 3.0 cm? b. Microwave signals are beamed between two mountaintops 50 km apart. How long does it take a signal to travel from one mountaintop to the other?

a. An FM radio station broadcasts at a frequency of I 01 .3 MHz. What is the wavelength? b. What is the frequency of a sound source that produces the same wavelength in 20C air?

Sound is detected when a sound wave causes the eardrum to vibrate (see Figure 14.26). Typically, the diameter of the eardrum is about 8.4 mm in humans. When someone speaks to you in a normal tone of voice, the sound intensity at your ear is approximately 1.0 X I0- 6 Wlm2 . How much energy is delivered to your eardrum each second?

At a rock concert, the sound intensity 1.0 m in front of the bank of loudspeakers is 0. 10 Wlm2 A fan is 30 m from the loud speakers. Her eardrums have a diameter of 8.4 mm. How much sound energy is transferred to each eardrum in 1.0 second?

The intensity of electromagnetic waves from the sun is 1.4 kW/m2 just above the earth's atmosphere. Eighty percent of this reaches the surface at noon on a clear summer day. Suppose you model your back as a 30 cm X 50 cm rectangle. How many joules of solar energy fall on your back as you work on your tan for 1.0 h?

The sun emits electromagnetic waves with a power of 4.0 x I026W. Determine the intensity of electromagnetic waves from the sun just outside the atmospheres of (a) Venus, (b)Mars, and (c) Saturn. Refer to the table of astronomical data inside the back cover.

A large solar panel on a spacecraft in Earth orbit produces 1.0 kW of power when the panel is turned toward the sun. What power would the solar cell produce if the spacecraft were in orbit around Saturn, 9.5 ti.mes as far from the sun?

Solar cells convert the energy of incoming light to electric energy; a good quality cell operates at an efficiency of 15%. Each person in the United States uses energy (for lighting, heating, transportation, etc.) at an average rate of 11 kW. Although sunlight varies with season and time of day, solar energy falls on the United States at an average intensity of 200 W/m2 . Assuming you live in an average location, what total solar-cell area would you need to provide all of your energy needs with energy from the sun?

LASIK eye surgery uses pulses of laser light to shave off tis sue from the cornea, reshaping it. A typical LASIK laser emits a 1.0-mm-diameter laser beam with a wavelength of 193 nm. Each laser pulse lasts 15 ns and contains 1.0 mJ of light energy. a. What is the power of o ne laser pulse? b. During the very brief time of the pulse, what is the intensity of the light wave?

Atnoononasunnyday, theintensityofsunlight is IOOOW/m2 A student uses a c ircular lens 5.0 cm in diameter to focus light from the sun onto a 4.0-mm-diameter spot. a. How much light power does the lens capture? b. What is the intensity in the foc used spot?

Lasers can be used to drill or c ut material. One such laser generates a series of high-power pulses of light. Each pulse contains 500 mJ of energy and lasts 10 ns. A lens focuses the light to a 10-m-diameter circle. What is the light intensity during the pulse?

What is the sound intensity level of a sound with an intensity of3.0 x I0- 6 W/m2?

What is the sound intensity of a whisper at a distance of 2.0 m, in W / 1112? What is the corresponding sound intensity level in dB?

You hear a sound at 65 dB. What is the sound intensity level if the intensity of the sound is doubled?

The sound intensity from a jack hammer breaking concrete is 2.0 W /1112 at a distance of 2.0 111 from the point of impact. This is suffici ently loud to cause permanent hearing damage if the operator doesn' t wear ear protection. What are (a) the sound intensity and (b) the sound intensity level for a person watching from 50 m away?

A concert loudspeaker suspended high off the ground emits 35 W of sound power. A small microphone with a 1.0 cm2 area is 50 m from the speaker. What are (a) the sound intensity and (b) the sound intensity level at the position of the microphone?

A rock band playing an o utdoor concert produces sound at 120 dB 5.0 m away from their single working loudspeaker. What is the sound intensity level 35 m from the speaker?

Your ears are sensitive to differences in pitch, but they are not very sensitive to differences in intensity. You are not capable of detecting a difference in sound intensity level of less than 1 dB. By what factor does the sound intensity increase if the sound intensity level increases from 60 dB to 61 dB?

30 seconds of exposure to 115 dB sound can damage your hearing, but a much quieter 94 dB may begin to cause damage after 1 hour of continuous exposure.You are going to an outdoor concert, and you'll be standing near a speaker that emits 50 W of acoustic power as a spherical wave. What minimum distance should you be from the speaker to keep the sound intensity level below 94 dB?

A woman wearing an in-ear hearing aid listens to a television set BIO at a normal volume of approximately 60 dB. To hear it, she requires an amplification of 30 dB, so the hearing aid supplies sound at 90 dB to the ear canal, which we assume to be circular with a diameter of 7 .0 mm. What is the output power of the hearing aid?

An opera singer in a convertible sings a note at 600 Hz while cruising down the highway at 90 km/h. What is the frequency heard by a. A person standing beside the road in front of the car? b. A person standing beside the road behind the car?

An osprey's call is a distinct whistle at 2200 Hz. An osprey BIO calls while diving at you, to drive you away from her nest. You hear the call at 2300 Hz. How fast is the osprey approaching?

A whistle you use to call your hunting dog has a frequency of 21 kHz, but your dog is ignoring it. You suspect the whistle may not be working, but you can't hear sounds above 20 kHz. To test it, you ask a friend to blow the whistle, then you hop on your bicyc le. In which direction should you ride (toward or away from your friend) and at what minimum speed to know if the whistle is working?

An echocardiogram uses 4.4 MHz ultrasound to measure BIO blood flow in the aorta. The blood is moving away from the probe at 1.4 111/s. What is the frequency shift of the reflected ultrasound?

A friend of yours is loudly singing a single note at 400 Hz while driving toward you at 25.0 mis on a day when the speed of sound is 340 mis. a. What frequency do you hear? b. What frequency does your friend hear if you suddenly start singing at 400 Hz?

While anchored in the middle of a lake, you count exactly three waves hitting your boat every 10 s. You raise anchor and start motoring slowly in the same direction the waves are going. When traveling at 1.5 mis, you notice that exactly two waves are hitting the boat from behind every 10 s. What is the speed of the waves on the lake?

A Doppler blood flow unit emits ultrasound al 5.0 MHz. What is the frequency shift of the ultrasound reflected from blood moving in an artery at a speed of 0.20 mis?

A train whistle is heard at 300 Hz as the train approaches town. The train cuts its speed in half as it nears the station, and the sound of the whistle is then 290 Hz. What is the speed of the train before and after slowing down?

Oil explorers set off explosives to make loud sounds, then li sten for the echoes from underground oil deposits. Geologists suspect that there is oil under 500-m-deep Lake Physics. It's known that Lake Physics is carved out of a granite basin. Explorers detect a weak echo 0.94 s after exploding dynamite at the lake surface. If it's really oil, how deep will they have to drill into the granite to reach it?

A 2.0-m- long stri ng is under 20 N of tension. A pulse travels the length of the st(ing in 50 ms. What is the mass of the string?

A female orb spider has a mass of 0.50 g. She is suspended from a tree branch by a I .I m )ength of 0.0020-mm-diameter silk. Spider silk has a density of 1300 kglm3 . If you tap the branch and send a vibration down the thread, how long does it take to reach the spider?

A spider spins a web with silk threads of density 1300 kglm3 BIO and diameter 3.0 m. A typical tension in the radial threads of such a web is 7.0 mN. Suppose a fly hits this web. Which will reach the spider first: the very slight sound of the impact or the disturbance traveling along the radial thread of the web?

In 2003, an earthquake in Japan generated I. I Hz waves that traveled outward at 7.0 kmls. 200 km to the west, seismic instruments recorded a maximum acceleration of 0.25g along the east-west ax is. a. How muc h time elapsed between the earthquake and the first detection of the waves? b. Was this a transverse or a longitudinal wave? c. What was the wavelength? d. What was the maximum horizontal displacement of the ground as the wave passed?

A coyote can locate a sound source with good accuracy by compari ng the arrival times of a sound wave at its two ears. Suppose a coyote is listening to a bird whistling at 1000 Hz. The bird is 3.0 m away, directly in front of the coyote's right ear. The coyote's ears are 15 cm apart. a. What is the difference in the arrival time of the sound at the left ear and the right ear? b. What is the ratio of this t ime difference to the period of the sound wave? Hint: You are looking for the difference between two numbers that are nearly the same. What does this near equality imply about the necessary precision dmi ng intem1edia1e stages of the calculation?

An earthquake produces longitudinal P waves that travel outward at 8000 mis and transverse S waves that move at 4500 mis. A seismograph at some distance from the earthquake records the arrival of the S waves 2.0 min after the arrival of the P waves. How far away was the earthquake? You can assume that the waves travel in straight lines, although actual se ismic waves follow more complex routes.

Figure P 15.62 shows two snapshot graphs taken I 0 rns apart, with the blue curve being the first snapshot. What are the (a)wavelength, (b) speed, (c) frequency, and (d) amplitude of this wave?

Low-frequency vertical oscillations are one possible cause of BIO motion sickness, with 0.30 Hz having the strongest effect. Your boat is bobbing in place at just the right frequency to cause you the maximum discomfort. The water wave that is bobbing the boat has crests that are 30 m apart. a. What is the speed of the waves? b. What will be the boat's vertical oscillation frequency if you drive the boat at 5.0 mis in the direction of the oncoming waves?

A wave on a string is described by y(x, r) = (3.0 crn)X cos[27T(xl(2.4 m) + tl(0.20 s))], where xis in m and r ins. a. In what direction is this wave traveling? b. What are the wave speed, frequency, and wavelength? c. At t = 0.50 s, what is the displacement of the string at x= 0.20 m?

Write the y-equation for a wave traveling in the negative x-direction with wavelength 50 cm, speed 4.0 mis, and amplitude 5.0 cm.

Write the y-equation for a wave traveling in the positive x-direction with frequency 200 Hz, speed 400 mis, and amplitude 0.0 I 0 mm.

A wave is described by the expression y(x, r) = (3.0 cm)X cos( I .5x - 501), where x is in m and r is in s. What is the speed of the wave and in what direction is it traveling?

A point OI) a string undergoes simple harmonic motion as a sinusoidal wave passes. When a sinusoidal wave with speed 24 mis, wavelength 30 cm, and amplitude of 1.0 cm passes, what is the maximum speed of a point on the string?

a. A typical I 00 W lightbulb produces 4.0 W of visible light. (The other 96 Ware dissipated as heat and infrared radiation.) What is the light intensity on a wall 2.0 m away from the lightbulb? b. A krypton laser produces a cylindrical red laser beam 2.0 mm in diameter with 2.0 W of power. What is the light intensity on a wall 2.0 m away from the laser?

The total power consumption by all humans on earth is approximately I013 W. Let's compare this to the power of incoming solar radiation. The intensity of radiation from the sun al the top of the atmosphere is 1380 Wlm2. The earth's radius i 6.37 X I 06 m. a. What is the total solar power received by the earth? b. By what factor does this exceed the total human power consumption?

A dark blue cylindrical bottle is 22 cm high and has a diamINT eter of 7 .0 cm. It is filled with water. The boll le absorbs 60% of the light that shines on it as it lies on its side in the noonday sun, with intensity 1000 Wlm2 By how much wi ll the temperature of the water increase in 5.0 min if there's negligible heat loss to the surrounding air?

Assume that the opening of the ear canal has a diameter of 7.0 mm. For this problem, you can ignore any focusing of energy into the opening by the pinna, the external folds of the ear. a. How much sound power is "captured" by one ear al 0 dB, the threshold of hearing? b. How much energy does one ear "capture" during I hour of listening to a lecrure delivered at a conversational volume of 60 dB?

The sound intensity 50 m from a wailing tornado siren is 0.10 Wlm2 . What is the sound intensity level 300 m from the siren?

One of the loudest sound generators ever created is the Danley Sound Labs Matterhorn. When run at full power, the device uses an input power of 40,000 W. The output power registers 94 dB at 250 m. Whal is the e fficiency of this devicethat is, the ratio of output power to input power?

A harvest mouse can detect sounds below the threshold of human hearing, as quiet as - I 0 dB. Suppose you are sitting in a field on a very quiet day while a harvest mouse sits nearby. A ve1y gentle breeze causes a leaf 1.5 m from your head to mstle, generating a faint sound right at the limit of your ability to hear it. The sound of the mstling leaf is also light at the threshold of hearing of the harvest mouse. How far is the harvest mouse from the leaf?

A speaker at an open-air concert emits 600 W of sound power radiated equally in all directions. a. What is the intensity of the sound 5.0 m from the speaker? b. What sound intensity level would you experience there if you did not have any protection for your ears? c. Earplugs you can buy jn the drugstore have a noise reduction rating of 23 decibels. If you are wearing those earplugs but your friend Phil is nor, how far from the speaker should Phil stand to experience the same loudness as you?

A physics professor demonstrates the Doppler effect by tying a 600 Hz sound generator to a 1.0-m-long rope and whirling it around her head in a horizontal circle at 100 rpm. What are the highest and lowest frequencies heard by a student in the classroom? Assume the room temperature is 20C.

When the heart pumps blood into the aorta, the pressure gradieni-the difference between the blood pressure inside INT the heart and the blood pressure in the artery-is an important diagnostic measurement. A direct measurement of the pressure gradient is difficult, but an indirect detem1ination can be made by inferring the pressure difference from a measurement of velocity. Blood is essentially at rest in the heart; when it leaves and enters the aorta, it speeds up significantly and-according to Bernoulli's equation- the pressure must decrease. A doctor using 2.5 MHz ultrasound measures a 6000 Hz frequency sh ift as the ultrasound reflects from blood ejected from the heart. a. What is the speed of the blood in the aorta? b. What is the difference in blood pressure between the inside of the heart and the aorta? Assume that the patient is lying down and that there is no difference in height as the blood moves from the heart into the ao1ta.

Although we can't hear them, the ultrasonic pulses are very loud. In order not to be deafened by the sound they emit, bats can temporarily turn off their hearing. Muscles in the ear cause the bones in their middle ear to separate slightly, so that they don' t transmit vibrations to the inner ear. After an ultrasound pulse ends, a bat can hear an echo from an object a minimum of l m away. Approximately how much time after a pulse is emitted is the bat ready to hear its echo? A. 0.5 ms B. I ms C. 3 ms D. 6 ms

Bats are sensitive to very small changes in frequency of the reflected waves. What information does this allow them to determine about their prey? A. Size B. Speed C. Distance D. Species

Some bats have specially shaped noses that focus ultrasound echolocation pulses in the forward direction. Why is this useful? A. Increasing intensity reduces the time delay for a reflected pulse. B. The energy of the pulse is concentrated in a smaller area, so the intensity is larger; reflected pulses will have a larger intensity as well. C. increasing intensity allows the bat to use a lower frequency and still have the same spatial resolution.

Some bats utilize a sound pulse with a rapidly decreasing frequency. A decreasing-frequency pulse has A. Decreasing wavelength. B. Decreasing speed. C. Increasing wavelength. ') D. Increasing speed.