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physics
electricity and magnetism
Conceptual Physics 11th edition Paul G. Hewitt - Solutions
The nearest star beyond the Sun is Alpha Centauri, 4.2 × 1016 m away. If we were to receive a radio message from this star today, show that it would have been sent 4.4 years ago.
A ball with the same diameter as a light bulb is held halfway between the bulb and a wall, as shown in the sketch. Construct light rays (similar to those in Figure 26.14) and show that the diameter of the umbra on the wall is the same as the diameter of the ball and that the diameter of the
A certain radar installation tracks airplanes by transmitting electromagnetic radiation of wavelength 3 cm. (a) Show that the frequency of this radiation is 10 GHz. (b) Show that the time required for a pulse of radar waves to reach an airplane 5 km away and return is 3.3 × 10-5s.
The wavelength of light changes as light goes from one medium to another, while the frequency remains the same. Is the wavelength longer or shorter in water than in air? Explain in terms of the equation speed = frequency × wavelength. A certain blue-green light has a wavelength of 600 nm (6 ×
When astronomers observe a supernova explosion in a distant galaxy, they see a sudden, simultaneous rise in visible light and other forms of electromagnetic radiation. Is this evidence to support the idea that the speed of light is independent of frequency? Explain.
What are the similarities and differences between radio waves and light?
Why would you expect the speed of light to be slightly less in the atmosphere than in a vacuum?
If you fire a bullet through a board, it will slow down inside and emerge at a speed that is less than the speed at which it entered. Does light, then, similarly slow down when it passes through glass and also emerge at a lower speed? Defend your answer.
Pretend that a person can walk only at a certain pace- no faster, no slower. If you time her uninterrupted walk across a room of known length, you can calculate her walking speed. If, however, she stops momentarily along the way to greet others in the room, the extra time spent in her brief
Is glass transparent or opaque to light of frequencies that match its own natural frequencies? Explain.
What determines whether a material is transparent or opaque?
Suppose that sunlight falls both on a pair of reading glasses and on a pair of dark sunglasses. Which pair of glasses would you expect to become warmer? Defend your answer.
Why does a high-flying airplane cast little or no shadow on the ground below while a low-flying airplane casts a sharp shadow?
Only some of the people on the daytime side of Earth can witness a solar eclipse when it occurs, whereas all the people on the nighttime side of Earth can witness a lunar eclipse when it occurs. Why is this so?
Lunar eclipses are always eclipses of a full Moon. That is, the Moon is always seen full just before and after Earth's shadow passes over it. Why is this? Why can we never have a lunar eclipse when the Moon is in its crescent or half-moon phase?
What astronomical event would be seen by observers on the Moon at the time Earth experiences a lunar eclipse? At the time Earth experiences a solar eclipse?
Light from a location on which you concentrate your attention falls on your fovea, which contains only cones. If you wish to observe a weak source of light, like a faint star, why should you not look directly at the source?
Why do objects illuminated by moonlight lack color?
Why should you be skeptical when your sweetheart holds you and looks at you with constricted pupils and says, "I love you"?
From your experimentation with Figure 26.16, is your blind spot located noseward from your fovea or to the outside of it?
Can we infer that a person with large pupils is generally happier than a person with small pupils? If not, why not?
The intensity of light decreases as the inverse square of the distance from the source. Does this mean that light energy is lost? Explain.
Light from a camera flash weakens with distance in accord with the inverse-square law. Comment on an airline passenger who takes a flash photo of a city at nighttime from a high flying plane.
Ships determine the ocean depth by bouncing sonar waves from the ocean bottom and measuring the round-trip time. How do some airplanes similarly determine their distance to the ground below?
When we look at the Sun, we are seeing it as it was 8 minutes ago. So we can only see the Sun "in the past." When you look at the back of your own hand, do you see it "now" or in "the past"?
"20/20 vision" is an arbitrary measure of vision-meaning that you can read what an average person can read at a distance of 20 feet in daylight. What is this distance in meters?
We hear people talk of "ultraviolet light" and "infrared light." Why are these terms misleading? Why are we less likely to hear people talk of "radio light" and "X-ray light"?
Suppose that two flashlight beams are shone on a white screen, one through a pane of blue glass and the other through a pane of yellow glass. What color appears on the screen where the two beams overlap? Suppose, instead, that the two panes of glass are placed in the beam of a single flashlight.
Does color television operate by color addition or by color subtraction? Defend your answer.
In a boutique store with only fluorescent lighting, a customer insists on taking dresses into the daylight at the doorway to check their color. Is she being reasonable? Explain.
Science author Suzanne Lyons is shown with son Tristan wearing red and daughter Simone wearing green in the opening set of photos for this chapter. Note that the negative of the photo shows these colors differently. What is your explanation?
In which of these cases will a ripe banana appear black-when illuminated with red, yellow, green, or blue light?
By reference to Figure 27.9, complete the following equations: Yellow light + blue light = ________light Green light + ______ light = white light Magenta + yellow + cyan = ________light
Why is the sky a darker blue when you are at high altitudes?
At the beach, you can get a sunburn while under the shade of an umbrella. What is your explanation?
Pilots sometimes wear glasses that transmit yellow light and absorb light of most other colors. Why does this help them see more clearly?
Why will the leaves of a red rose be warmed more than the petals when illuminated with red light? How does this relate to people in the hot desert wearing white clothes?
Why does smoke from a campfire look blue against trees near the ground but yellow against the sky?
If the sky on a certain planet in the solar system were normally orange, what color would sunsets be?
Tiny particles, like tiny bells, scatter high-frequency waves more than low-frequency waves. Large particles, like large bells, mostly scatter low-frequency waves. Intermediate-size particles and bells mostly scatter waves of intermediate frequencies. How does this relate to the whiteness of clouds?
Very big particles, like droplets of water, absorb more radiation than they scatter. How does this relate to the darkness of rain clouds?
How would the whiteness of snow appear if Earth's atmosphere were several times denser?
The atmosphere of Jupiter is more than 1000km thick. From the surface of Jupiter, would you expect to see a white Sun?
If the sunlight were somehow green instead of white, what color clothing would be most advisable on an uncomfortably hot day? On a very cold day?
You're explaining to a youngster at the seashore why the water is cyan colored. The youngster points to the white-caps of overturning waves and asks why they are white. What is your answer?
Why do we not list black and white as colors?
Why are the interiors of optical instruments intentionally black?
Wheels from a toy cart are rolled from a concrete sidewalk onto the following surfaces: A, a paved driveway; B, a grass lawn; C, close-cropped grass on a golf-course putting green. Due to slowing, each set of wheels bends at the boundary and is deflected from its initial straight-line course. Rank
Identical rays of light enter three transparent blocks composed of different materials. Light slows down upon entering the blocks. Rank the blocks according to the speed light travels in each, from highest speed to lowest speed.
Identical rays of light in air are refracted upon entering three transparent materials: A, water, where the speed of light is 0.75c; B, ethyl alcohol (speed 0.7 c); C, crown glass (speed 0.6c). Rank the materials according to how much the light ray bends toward the normal, from most bending to
Car mirrors are uncoated on the front surface and silvered on the back surface. When the mirror is properly adjusted, light from behind reflects from the silvered surface into the driver's eyes. Good. But this is not so good at nighttime with the glare of headlights behind. This problem is solved
To reduce glare from the surroundings, the windows of some department stores, rather than being vertical, slant inward at the bottom. How does this reduce glare?
A person in a dark room looking through a window can clearly see a person outside in the daylight, whereas the person outside cannot see the person inside. Explain.
Which kind of road surface is easier to see when driving at night-a pebbled, uneven surface or a mirror-smooth surface? And why is it difficult to see the roadway in front of you when driving on a rainy night?
What must be the minimum length of a plane mirror in order for you to see a full image of yourself?
What effect does your distance from the plane mirror have in your answer to the preceding exercise?
On a steamy mirror, wipe away just enough to see your full face. How tall will the wiped area be compared with the vertical dimension of your face?
Hold a pocket mirror almost at arm's length from your face and note how much of your face you can see. To see more of your face, should you hold the mirror closer or farther away, or would you have to have a larger mirror?
The diagram shows a person and her twin at equal distances on opposite sides of a thin wall. Suppose a window is to be cut in the wall so each twin can see a complete view of the other. Show the size and location of the smallest window that can be cut in the wall to do the job.
In the opening photo of the duck standing on the rock, why are the duck's feet not shown in the reflected view?
Why does reflected light from the Sun or Moon appear as a column in the body of water as shown? How would the reflected light appear if the water surface were perfectly smooth?
What is wrong with the cartoon of the man looking at himself in the mirror? (Have a friend face a mirror as shown, and you'll see.)
A pair of toy cart wheels is rolled obliquely from a smooth surface onto two plots of grass, a rectangular plot and a triangular plot, as shown. The ground is on a slight incline so that, after slowing down in the grass, the wheels will speed up again when emerging on the smooth surface. Finish
During a lunar eclipse, the Moon is not completely dark but is usually a deep red in color. Explain this in terms of the refraction of all the sunsets and sunrises around the world.
A beam of light bends as shown in (a), while the edges of the immersed square bend as shown in (b). Do these pictures contradict each other? Explain.
If, while standing on a bank, you wish to spear a fish beneath the water surface in front of you, should you aim above, below, or directly at the observed fish to make a direct hit? If, instead, you zap the fish with a laser, should you aim above, below, or directly at the observed fish? Defend
In the other opening photo of physics teacher Fred Myers taking a photo of his daughter McKenzie, how many mirrors were involved? Explain.
If the fish in the previous exercise were small and blue and your laser light were red, what corrections should you make? Explain.
When a fish in a pond looks upward at an angle of 45°, does it see the sky above the water's surface or a reflection from the water-air boundary of the bottom of the pond? Defend your answer.
Upward rays of light in water toward the water-air boundary at angles greater than 48° to the normal are totally reflected. No rays beyond 48° refract outside. How about the reverse? Is there an angle at which light rays in air meeting the air-water boundary will totally reflect? Or will some
If you were to send a beam of laser light to a space station above the atmosphere and just above the horizon, would you aim the laser above, below, or at the visible space station? Defend your answer.
What accounts for the large shadows cast by the ends of the thin legs of the water strider?
When you stand with your back to the Sun, you see a rainbow as a circular arc. Could you move off to one side and then see the rainbow as the segment of an ellipse rather than the segment of a circle (as Figure 28.32 suggests)? Defend your answer.
Two observers standing apart from one another do not see the "same" rainbow. Explain.
A rainbow viewed from an airplane may form a complete circle. Where will the shadow of the airplane appear? Explain.
How is a rainbow similar to the halo sometimes seen around the Moon on a frosty night? If you're stumped, check the web and see how rainbows and halos differ.
Fermat's principle is of least time rather than of least distance. Would least distance apply as well for reflection? For refraction? Why are your answers different?
Transparent plastic swimming-pool covers called solar heat sheets have thousands of small air-filled bubbles that resemble lenses. The bubbles in these sheets are advertised to focus heat from the Sun into the water, thereby raising its temperature. Do you think these bubbles direct more solar
Would the average intensity of sunlight measured by a light meter at the bottom of the pool in Figure 28.45 be different if the water were still?
Why will goggles allow a swimmer under water to focus more clearly on what he or she is looking at?
If a fish wore goggles above the water surface, why would vision be better for the fish if the goggles were filled with water? Explain.
Does a diamond under water sparkle more or less than in air? Defend your answer.
Cover the top half of a camera lens. What effect does this have on the pictures taken?
How could a converging lens be made for sound waves? (Such a lens, a spherical bag of gas, is a feature of San Francisco's Exploratorium.)
Would refracting telescopes and microscopes magnify if light had the same speed in glass as in air? Defend your answer.
Her eye at point P looks into the mirror. Which of the numbered cards can she see reflected in the mirror?
Why does the sharpness of the image in a pinhole camera not depend on the position of the viewing screen?
Whereas pinholes provide sharp images, lenses with large apertures are advantageous for spy cameras in high-flying aircraft. Why?
In terms of focal length, how far behind the camera lens is photosensitive surface located when very distant objects are being photographed?
Cowboy Joe wishes to shoot his assailant by ricocheting a bullet off a mirrored metal plate. To do so, should he simply aim at the mirrored image of his assailant? Explain.
Trucks often have signs on their back ends that say, "If you can't see my mirrors, I can't see you." Explain the physics here.
When you look at yourself in the mirror and wave your right hand, your beautiful image waves the left hand. Then why don't the feet of your image wiggle when you shake your head?
Show with a simple diagram that when a mirror with a fixed beam incident upon it is rotated through a certain angle, the reflected beam is rotated through an angle twice as large. (This doubling of displacement makes irregularities in ordinary window glass more evident.)
No glass is perfectly transparent. Mainly because of reflections, about 92% of light passes through an average sheet of clear windowpane. The 8% loss is not noticed through a single sheet, but through several sheets, the loss is apparent. How much light is transmitted by a double-paned window (one
The diameter of the Sun makes an angle of 0.53° from Earth. How many minutes does it take the Sun to move 1 solar diameter in an overhead sky? (Remember that it takes 24 hours, or 1440 minutes, for the Sun to move through 360°.) How does your answer compare with the time it takes the Sun to
Why can sunlight that illuminates Earth be approximated by plane waves, whereas the light from a nearby lamp cannot?
Suppose you place a diffraction grating in front of a camera lens and take a picture of illuminated streetlights. What will you expect to see in your photograph?
Why is Young's experiment more effective with slits than with the pinholes he first used?
In our everyday environment, diffraction is much more evident for sound waves than for light waves. Why is this so?
The colored wings of many butterflies are due to pigmentation, but in others, such as the Morpho butterfly, the colors do not result from any pigmentation. When the wing is viewed from different angles, the colors change. How are these colors produced?
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