Questions and Answers of Inquiry into Physics

Would an electromagnetic pump be able to move a liquid superconductor? Why or why not?
The nuclei of carbon atoms that are found in Nature come in two main “varieties” called isotopes. The carbon-14 nuclei have a greater mass than the carbon-12 nuclei. The two types of atoms can be
In the particular accelerator shown in Figure8.16, what are the possible directions of the magnetic field that keeps the particles traveling around the circular path?
What is the wavelength of the peak of the blackbody radiation curve for the human body (T = 310 K)? What type of EM wave is this?
Explain why a transformer doesn’t work with DC.
What is the frequency of the EM wave emitted most strongly by a glowing element on a stove with temperature 1,500 K?
What would an audio speaker like that shown in Figure8.23 do at the instant a low-voltage battery is connected to it? N N Voice coil AC in S S Speaker cone (a) Sound
What is the lowest temperature that will cause a black body to emit radiation that peaks in the infrared?
What is analog-to-digital conversion and how is it used in sound reproduction?
Explain how electromagnetic waves are a natural outcome of the principles of electromagnetism.
An electromagnetic wave travels in a region of space occupied only by a free electron. Describe the resulting motion of the electron.
List the main types of electromagnetic waves in order of increasing frequency. Give at least one useful application for each type of wave.
Alternating current with a frequency of 1 million Hz flows in a wire. What in particular could be detected traveling outward from the wire?
Aircraft equipped with powerful radar units are forbidden from using them when parked on the ground near people. Explain why this is so.
What is different about our perceptions of the different frequencies within the visible light band of the EM spectrum?
Which type of EM wave does your body emit most strongly?
A heat lamp is designed to keep food and other things warm. Would it also make a good tanning lamp? Why or why not?
How are x-rays produced?
Why are x-rays more strongly absorbed by bones than by muscles and other tissues?
What is blackbody radiation? In what ways does the radiation emitted by a blackbody change as its temperature increases?
A liquid compound is not heated by microwaves the way water is. What can you conclude about the nature of the compound’s molecules?
What are the main uses of microwaves? Explain how each process works.
What is the “motor-generator duality”? Explain how it is used.
Referring to the lightbulbs described in Question 30 and assuming the emitting areas of the filaments in the two bulbs are the same, which of the two is the brighter? About how much brighter is this
A lightbulb manufacturer makes bulbs with different “color temperatures,” meaning that the spectrum of light they emit is similar to a blackbody with that temperature. What would be the
Explain how infrared light can be used to detect some types of animals in the dark. Can you think of a situation in which this would not work?
What effect does the ozone layer have on the EM waves from the Sun? What is currently threatening the ozone layer?
Describe the greenhouse effect that is occurring in Earth’s atmosphere.
How does the ionosphere affect the range of radio communications?
Five transformers, all with the same basic construction (Figure 8.52), have different numbers of turns of wire as their input, N in , and output, Nout, coils according to the circumstances given
Six blackbody radiators have temperatures and emitted powers as given. Rank these blackbodies according to their emitting surface areas from smallest to largest. Justify your rankings based on your
A camera is equipped with a telephoto lens that has a focal length of 200 mm. Repeat part (c) of Challenge 8 for this situation.Repeat part (c) of Challenge 8 (c) The kitten is then photographed from
How would Figure 9.29a be different if the glass were replaced by water or by diamond? (a) Partial reflection Air Glass
Of the three converging lenses shown in Figure 9.44, which would you expect to have the shortest focal length? Why? Converging Diverging Converging Diverging Converging Diverging DI JL (( (a) (b) (c)
Referring to Figure 9.64, why doesn’t the ray inside each of the two prisms get refracted out of the prisms at the second interface instead of turned back into the glass? Similarly, referring to
It is determined by immersing a crown in water that its volume is 26 in.3 5 0.015 ft3.(a) What would its weight be if it were made of pure gold?(b) What would its weight be if its volume were half
It is easier for a person to float in the ocean than in an ordinary swimming pool. Why?
An empty storage tank has a volume of 1,500 ft3. What is the buoyant force exerted on it by the air?
The “suction cup” (Figure 4.54) is a common device used to suspend pictures, plants, and other objects from walls, ceilings, windows, and other smooth surfaces. Why is the name “suction cup”
Why does the buoyant force always act upward?
A modern-day zeppelin holds 8,000 m3 of helium. Compute its maximum payload at sea level.
What substances would sink in gasoline but float in water?
A juniper-wood plank measuring 0.25 ft by 1 ft by 16 ft is totally submerged in water.(a) What is its weight?(b) What is the buoyant force acting on it?(c) What is the size and the direction of the
A ship on a large river approaches a bridge, and the captain notices that the ship is about a foot too tall to fit under the bridge. A crew member suggests pumping water from the river into an empty
In “The Unparalleled Adventure of One Hans Pfaall” by Edgar Allen Poe, the hero discovers a gas whose density is “37.4 times” less than that of hydrogen. How much better at lifting would a
A boat (with a flat bottom) and its cargo weigh 5,000 N. The area of the boat’s bottom is 4 m2. How far below the surface of the water is the boat’s bottom when it is floating in water?
A brick is tied to a balloon filled with air and then tossed into the ocean. As the balloon is pulled downward by the brick, the buoyant force on it decreases. Why?
Venus’s atmosphere is much more dense than Earth’s whereas that of Mars is far less dense. Suppose it is decided to send a probe to each planet that, once it arrived, would be carried around in
What is Pascal’s principle?
How does a car’s brake system make use of Pascal’s principle?
A booster pump on a brake system designed to be used horizontally consists of two cylinders capped by pistons connected by a hose. The cylinders and hose are filled with an incompressible fluid. The
A solid cube is completely submerged in a particular liquid and floats at a constant level. When the temperature of the liquid and the solid is raised, the liquid expands more than the solid. Will
Smoking was a common habit in the United States in times past, and nonsmokers riding in cars where another passenger had lit up quickly learned to open their window a crack while the car was moving
When two trains, going in opposite directions, are passing on tracks that are laid out close together, the train cars can often be seen to be leaning in toward one another where they are in
The volume flow rate in an artery that supplies blood to the brain is 3.5 x 1026 m3/s. If the cross-sectional area of the artery is 8.5 x 1025 m2, what is the average speed of the blood through this
What important thing happens when the speed of a moving fluid increases?
The pressure in the air along the upper surface of an aircraft’s wing (in flight) is lower than the pressure along the lower surface. Compare the speed of the air flowing over the wing to that of
How does a perfume atomizer make use of Bernoulli’s principle?
Explain why a smoothly flowing stream of water from a faucet often gets progressively narrower in cross-section as the water falls.
Corrugated plastic pipes are commonly used to carry water away from the foundation areas of houses. These accordionlike pipes typically vary in diameter, alternating between smaller and larger
When white light undergoes interference by passing through narrow slits, dispersion occurs. Why? What is the ordering of the various colors, starting from the middle of the pattern?
In a double-slit interference experiment, a special lamp emitting yellow light from heated sodium atoms is used to produce an interference pattern on a screen located 1.50 m from a pair of slits
A ray of yellow light crosses the boundary between glass and air, going from the glass into air. If the angle of incidence is 20°, what is the angle of refraction?
The “shell” of a concept map dealing with lenses and their properties is shown in Concept Map 9.2. Most of the concepts and all of the linking phrases needed to form meaningful propositions have
Using Figure 9.34, find the angles of refraction for a light ray passing from air into glass with the following angles of incidence: 5°, 10°, and 20°. Do you notice a trend in the resulting
While above water, a swimmer’s eyes are focused on a nearby boat. When the swimmer submerges, the underwater part of the boat will not be in focus even though it is the same distance away and the
The form of the lens formula used most commonly in physics isUse this to derive an equation that gives s in terms of p and f. f 1 S p
A fish looks up toward the surface of a pond and sees the entire panorama of clouds, sky, birds, and so on, contained in a narrow cone of light, beyond which there is darkness. What is going on here
A person looking straight down on a thin film of oil on water sees the color red. How thick could the film be to cause this? How thick could it be at another place where violet is seen?
A camera is used to photograph a kitten. The camera is equipped with a standard lens that has a focal length of 50 mm. The camera is focused by moving the lens closer to or farther away from the film
A 2.0-cm-tall object stands in front of a converging lens. It is desired that a virtual image 2.5 times larger than the object be formed by the lens. How far from the lens must the object be placed
Why can’t you go to the end of a rainbow? What happens to the rainbow when you walk toward one of its ends?
For a given slit spacing, a, and wavelength, λ, if the screen distance, S, is increased, what happens to the fringe spacing—that is, the distance between adjacent bright regions in a typical
A person looks at a statue that is 2 m tall. The image on the person’s retina is inverted and 0.005 m high. What is the magnification?
If the separation, a, between the slits in a double slit interference experiment is reduced, then, for a fixed value of screen distance, S, and wavelength of light, λ, how will the separation, Δx,
What is the magnification in Problem 7?Data from Problem 7A camera is equipped with a lens with a focal length of 30 cm. When an object 2 m (200 cm) away is being photographed, how far from the film
A small object is placed to the left of a convex lens and on its optical axis. The object is 30 cm from the lens, which has a focal length of 10 cm. Determine the location of the image formed by the
If the object in Problem 12 is moved toward the lens to a position 8 cm away, what will the image position be? Describe the nature of this new image.Data from in Problem 12A small object is placed to
Gamma rays (γ-rays) are high-energy photons. In a certain nuclear reaction, a γ-ray of energy 0.511 MeV (million electron volts) is produced. Compute the frequency of such a photon.
The rate at which solar wind particles enter the atmosphere is higher during the day than at night, yet the intensity of the auroral emissions remains high well after the Sun has set. Can you suggest
One serious problem with sending intense laser beams long distances through the atmosphere to receiving targets is that the beams spread out. This effect, called thermal blooming, is caused by the
Things around you are emitting infrared radiation that includes the wavelength 9.9 x 10-6 m. What is the energy of these IR photons?
Compute the approximate ratio of the amount of blue light in scattered sky light to the amount of orange.
The equation connecting s, p, and f for a simple lens can be employed for spherical mirrors, too. A concave mirror with a focal length of 8 cm forms an image of a small object placed 10 cm in front
The focal length of a diverging lens is negative. If f = -20 cm for a particular diverging lens, where will the image be formed of an object located 50 cm to the left of the lens on the optical axis?
(a) In a camera equipped with a 50-mm focal-length lens, the maximum distance that the lens can be from the film is 60 mm. What is the smallest distance an object can be from the camera if its image
Why don’t we generally notice the effects of special relativity in our daily lives? Be specific.
Referring to Figure10.35, notice that the bremsstrahlung x-ray spectrum of both Mo and W cut off (have zero intensity) at about 0.035 nm. Figure 10.35X-rays with this wavelength are produced by the
If you bombard hydrogen atoms in the ground state with a beam of particles, the collisions will sometimes excite the atoms into one of their upper states. What is the minimum kinetic energy the
Compute a rough estimate of the number of photons emitted each second by a 100-W lightbulb. You might make the simplifying assumptions that (1) All of the electrical energy is converted into
In the Bohr model for hydrogen, the radius of the nth orbit can be shown to be n2 times the radius of the first Bohr orbit r1 = 0.05 nm. Similarly, the energy of an electron in the nth orbit is 1/n2
Referring to Figure10.36, we see that the atomic number Z is proportional to f1/2 or that Z2 is proportional to f. Because the frequency of the characteristic x-ray lines is itself proportional to
In a typical electron microscope, the momentum of each electron is about 1.6 x 10-22 kg-m/s. What is the de Broglie wavelength of the electrons?
Long before the advent of quantum mechanics, physicists had developed an empirical formula to predict the wavelengths of the emission lines of hydrogen. Specifically, for an electron transition from
If a proton were traveling the same speed as electrons in Problem 5, what would its de Broglie wavelength be? The mass of a proton is 1.67 x 10-27 kg.
(a) A small ball with a mass of 0.06 kg moves along a circular orbit with a radius of 0.5 m at a speed of 3.0 m/s. What is the angular momentum of the ball?(b) If the angular momentum of this ball
A hydrogen atom initially in the n = 3 level emits a photon and ends up in the ground state.(a) Compute the energy of the emitted photon?(b) If this atom then absorbs a second photon and returns to
A neutral calcium atom (Z = 20) is in its ground state electronic configuration. How many of its electrons are in the n = 3 level? Explain how you arrived at your answer.
In a helium-neon laser, find the energy difference between the two levels involved in the production of red light of wavelength 632.8 nm by this system.
Describe the operation of a pulsed ruby laser.

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