Misconceptual questions Physics 1201 Final Exam

26-6. Spaceships A and B are traveling directly toward each other at a speed 0.5c relative to the Earth, and each has a headlight aimed toward the other ship. What value do technicians on ship B get by measuring the speed of the light emitted by ship A's headlight?

(a) 0.5c. (b) 0.75c. (c) 1.0c. (d) 1.5c. Answer: C

19-4. Two identical 10-V batteries and two identical 10-Ω resistors are placed in series as shown in Fig. 19-42. If a 10-Ω lightbulb is connected with one end connected between the batteries and other end between the resistors, how much current will flow through the lightbulb?

(a) 0A. (b) 1A. (c) 2A. (d) 4A. Answer: A

26-3. For the flashing of the flashlight in MisConceptual Question 2, what time interval is the proper time interval?

(a) 1.15 s. (b) 1.00 s. (c) 0.87 s. (d) 0.13 s. Answer: C

21-14. A 10-V, 1.0-A dc current is run through a step-up transformer that has 10 turns on the input side and 20 turns on the output side. What is the output?

(a) 10 V, 0.5 A. (b) 20 V, 0.5 A. (c) 20 V, 1 A. (d) 10 V, 1 A. (e) 0V, 0A. Answer: E

26- 1. The fictional rocket ship Adventure is measured to be 50 m long by the ship's captain inside the rocket. When the rocket moves past a space dock at 0.5c, space-dock personnel measure the rocket ship to be 43.3 m long. What is its proper length?

(a) 50m. (b) 43.3 m. (c) 93.3 m. (d) 13.3 m. Answer: A

24-2. Light from a green laser of wavelength 530 nm passes through two slits that are 400 nm apart. The resulting pattern formed on a screen in front of the slits is shown in Fig. 24-55. If point A is the same distance from both slits, how much closer is point B to one slit than to the other?

(a) 530 nm. (b) 265 nm. (c) 400 nm. (d) 0 nm. (e) It depends on the distance to the screen. Answer: A

19-3. A 10,000-Ω resistor is placed in series with a 100-Ω resistor. The current in the 10,000-Ω resistor is 10 A. If the resistors are swapped, how much current flows through the 100-Ω resistor?

(a) >10 A. (b) <10 A. (c) 10 A. (d) Need more information about the circuit. Answer: C

25-2. What is a megapixel in a digital camera?

(a) A large spot on the detector where the image is focused. (b) A special kind of lens that gives a sharper image. (c) A number related to how many photographs the camera can store. (d) A million light-sensitive spots on the detector. (e) A number related to how fast the camera can take pictures. Answer: D

25-11. Which of the following statements is true?

(a) A larger-diameter lens can better resolve two distant points. (b) Red light can better resolve two distant points than blue light can. (c) It is easier to resolve distant objects than nearer objects. (d) Objects that are closer together are easier to resolve than objects that are farther apart. Answer: A

20-1. Indicate which of the following will produce a magnetic field:

(a) A magnet. (b) The Earth. (c) An electric charge at rest. (d) A moving electric charge. (e) An electric current. (f) The voltage of a battery not connected to anything. (g) An ordinary piece of iron. (h) A piece of any metal. Answer: A,B,D,E

20-6. Which statements about the force on a charged particle placed in a magnetic field are true?

(a) A magnetic force is exerted only if the particle is moving. (b) The force is a maximum if the particle is moving in the direction of the field. (c) The force causes the particle to gain kinetic energy. (d) The direction of the force is along the magnetic field. (e) A magnetic field always exerts a force on a charged particle. Answer: D

23-13. Which of the following can form an image?

(a) A plane mirror. (b) A curved mirror. (c) A lens curved on both sides. (d) A lens curved on only one side. (e) All of the above. Answer: E

23-7. When moonlight strikes the surface of a calm lake, what happens to this light?

(a) All of it reflects from the water surface back to the air. (b) Some of it reflects back to the air; some enters the water. (c) All of it enters the water. (d) All of it disappears via absorption by water molecules. Answer: B

22-5. In empty space, which quantity is always larger for X-ray radiation than for a radio wave?

(a) Amplitude. (b) Wavelength. (c) Frequency. (d) Speed. Answer: C

24-10. When a CD is held at an angle, the reflected light contains many colors. What causes these colors?

(a) An anti-theft encoding intended to prevent copying of the CD. (b) The different colors correspond to different data bits. (c) Light reflected from the closely spaced grooves adds constructively for different wavelengths at different angles. (d) It is part of the decorative label on the CD. Answer:C

17-8. Which of the following do not affect capacitance?

(a) Area of the plates. (b) Separation of the plates. (c) Material between the plates. (d) Charge on the plates. (e) Energy stored in the capacitor. Answer: D,E

23-3. You want to create a spotlight that will shine a bright beam of light with all of the light rays parallel to each other. You have a large concave spherical mirror and a small light-bulb. Where should you place the lightbulb?

(a) At the focal point of the mirror. (b) At the radius of curvature of the mirror. (c) At any point, because all rays bouncing off the mirror will be parallel. (d) None of the above; you can't make parallel rays with a concave mirror. Answer: A

18-10. Nothing happens when birds land on a power line, yet we are warned not to touch a power line with a ladder. What is the difference?

(a) Birds have extremely high internal resistance compared to humans. (b) There is little to no voltage drop between a bird's two feet, but there is a significant voltage drop between the top of a ladder touching a power line and the bottom of the ladder on the ground. (c) Dangerous current comes from the ground only. (d) Most birds don't understand the situation. Answer: B

24-12. If unpolarized light is incident from the left on three polarizers as shown in Fig. 24-57, in which case will some light get through?

(a) Case 1 only. (b) Case 2 only. (c) Case 3 only. (d) Cases 1 and 3. (e) All three cases. Answer: B

21-11. Which of the following can a transformer accomplish?

(a) Changing voltage but not current. (b) Changing current but not voltage. (c) Changing power. (d) Changing both current and voltage. Answers: D

25-6. How do eyeglasses help a nearsighted person see more clearly?

(a) Diverging lenses bend light entering the eye, so the image focuses farther from the front of the eye. (b) Diverging lenses bend light entering the eye, so the image focuses closer to the front of the eye. (c) Converging lenses bend light entering the eye, so the image focuses farther from the front of the eye. (d) Converging lenses bend light entering the eye, so the image focuses closer to the front of the eye. (e) Lenses adjust the distance from the cornea to the back of the eye. Answer: A

17-10. Which of the following is a vector?

(a) Electric potential. (b) Electric potential energy. (c) Electric field. (d) Equipotential lines. (e) Capacitance. Answer: C

26-2. As rocket ship Adventure (MisConceptual Question 1) passes by the space dock, the ship's captain flashes a flashlight at 1.00-s intervals as measured by space-dock personnel. How often does the flashlight flash relative to the captain?

(a) Every 1.15 s. (b) Every 1.00 s. (c) Every 0.87 s. (d) We need to know the distance between the ship and the space dock. Answer: C

16-3.Fred the lightning bug has a mass m and a charge +q. Jane, his lightning-bug wife, has a mass of m and a charge -2q. Because they have charges of opposite sign, they are attracted to each other. Which is attracted more to the other, and by how much?

(a) Fred, twice as much. (b) Jane, twice as much. (c) Fred, four times as much. (d) Jane, four times as much. (e) They are attracted to each other by the same amount. Answer : E

17-4. Which of the following statements is valid?

(a) If the potential at a particular point is zero, the field at that point must be zero. (b) If the field at a particular point is zero, the potential at that point must be zero. (c) If the field throughout a particular region is constant, the potential throughout that region must be zero. (d) If the potential throughout a particular region is constant, the field throughout that region must be zero. Answer:D

25-12. While you are photographing a dog, it begins to move away. What must you do to keep it in focus?

(a) Increase the f-stop value. (b) Decrease the f-stop value. (c) Move the lens away from the sensor or film. (d) Move the lens closer to the sensor or film. (e) None of the above. Answer: D

21-5. If there is induced current in Question 18 (see Fig. 21-51), wouldn't that cost energy? Where would that energy come from in case (a)?

(a) Induced current doesn't need energy. (b) Energy conservation is violated. (c) There is less kinetic energy. (d) There is more gravitational potential energy. Answer: C

20-11. Which of the following statements about the force on a charged particle due to a magnetic field are not valid?

(a) It depends on the particle's charge. (b) It depends on the particle's velocity. (c) It depends on the strength of the external magnetic field. (d) It acts at right angles to the direction of the particle's motion. (e) None of the above; all of these statements are valid. Answer: E

23-8. If you shine a light through an optical fiber, why does it come out the end but not out the sides?

(a) It does come out the sides, but this effect is not obvious because the sides are so much longer than the ends. (b) The sides are mirrored, so the light reflects. (c) Total internal reflection makes the light reflect from the sides. (d) The light flows along the length of the fiber, never touching the sides. Answer : C

20-9. A proton enters a uniform magnetic field that is perpendicular to the proton's velocity (Fig. 20-51). What happens to the kinetic energy of the proton?

(a) It increases. (b) It decreases. (c) It stays the same. (d) It depends on the velocity direction. (e) It depends on the B field direction. Answer: B

16-1. Q1= - 0.10 μC is located at the origin. Q2=+0.10 μC is located on the positive x axis at x = 1.0 m. Which of the following is true of the force on Q1 due to Q2?

(a) It is attractive and directed in the +x direction. (b) It is attractive and directed in the -x direction. (c) It is repulsive and directed in the +x direction. (d) It is repulsive and directed in the -x direction. Answer: A

25-9. Why aren't white-light microscopes made with a magnification of 3000×?

(a) Lenses can't be made large enough. (b) Lenses can't be made small enough. (c) Lenses can't be made with short enough focal lengths. (d) Lenses can't be made with long enough focal lengths. (e) Diffraction limits useful magnification to several times less than this. Answer: E

18-2. When a battery is connected to a lightbulb properly, current flows through the lightbulb and makes it glow. How much current flows through the battery compared with the lightbulb?

(a) More. (b) Less. (c) The same amount. (d) No current flows through the battery. Answer: C

22-8. An electromagnetic wave is traveling straight down toward the center of the Earth. At a certain moment in time the electric field points west. In which direction does the magnetic field point at this moment?

(a) North. (b) South. (c) East. (d) West. (e) Up. (f) Down. (g) Either (a) or (b). (h) Either (c) or (d). (i) Either (e) or (f). Answer: A

18-3. Which of the following statements about Ohm's law is true?

(a) Ohm's law relates the current through a wire to the voltage across the wire. (b) Ohm's law holds for all materials. (c) Any material that obeys Ohm's law does so independently of temperature. (d) Ohm's law is a fundamental law of physics. (e) Ohm's law is valid for superconductors. Answer: A

19-5. Which resistor shown in Fig. 19-43 has the greatest current going through it? Assume that all the resistors are equal.

(a) R1. (b) R1 and R2. (c) R3 and R4. (d) R5. (e) All of them the same. Answer: D

22-3. Which of the following travel at the same speed as light? (Choose all that apply.)

(a) Radio waves. (b) Microwaves. (c) Radar. (d) Ultrasonic waves. (e) Infrared radiation. (f) Cell phone signals. (g) Gamma rays. (h) X-rays. Answer: Not D

22-4. Which of the following types of electromagnetic radiation travels the fastest?

(a) Radio waves. (b) Visible light waves. (c) X-rays. (d) Gamma rays. (e) All the above travel at the same speed. Answer: E

21-10. Which of the following will not increase a generator's voltage output?

(a) Rotating the generator faster. (b) Increasing the area of the coil. (c) Rotating the magnetic field so that it is more closely parallel to the generator's rotation axis. (d) Increasing the magnetic field through the coil. (e) Increasing the number of turns in the coil. Answers: C

24-9. If someone is around a corner from you, what is the main reason you can hear him speaking but can't see him?

(a) Sound travels farther in air than light does. (b) Sound can travel through walls, but light cannot. (c) Sound waves have long enough wavelengths to bend around a corner; light wavelengths are too short to bend much. (d) Sound waves reflect off walls, but light cannot. Answer: C

21-* 16. When you swipe a credit card, the machine sometimes fails to read the card. What can you do differently?

(a) Swipe the card more slowly so that the reader has more time to read the magnetic stripe. (b) Swipe the card more quickly so that the induced emf is higher. (c) Swipe the card more quickly so that the induced currents are reduced. (d) Swipe the card more slowly so that the magnetic fields don't change so fast. Answer: B

17-11. A + 0.2 C charge is in an electric field. What happens if that charge is replaced by a - 0.2 C charge?

(a) The electric potential changes sign, but the electric potential energy stays the same. (b) The electric potential stays the same, but the electric potential energy changes sign. (c) Both the electric potential and electric potential energy change sign. (d) Both the electric potential and electric potential energy stay the same. Answer: B

21-9. When a generator is used to produce electric current, the resulting electric energy originates from which source?

(a) The generator's magnetic field. (b) Whatever rotates the generator's axle. (c) The resistance of the generator's coil. (d) Back emf. (e) Empty space. Answer: B

17-7. When the proton and electron in MisConceptual Question 6 strike the opposite plate, which one has more kinetic energy?

(a) The proton. (b) The electron. (c) Both acquire the same kinetic energy. (d) Neither— there is no change in kinetic energy. (e) They both acquire the same kinetic energy but with opposite signs. Answer: C

17-6. A proton (Q = +e) and an electron (Q = -e) are in a constant electric field created by oppositely charged plates. You release the proton from near the positive plate and the electron from near the negative plate. Which feels the larger electric force?

(a) The proton. (b) The electron. (c) Neither—there is no force. (d) The magnitude of the force is the same for both and in the same direction. (e) The magnitude of the force is the same for both but in opposite directions. Ans:E

26-4. The rocket ship of MisConceptual Question 1 travels to a star many light-years away, then turns around and returns at the same speed. When it returns to the space dock, who would have aged less: the space-dock personnel or ship's captain?

(a) The space-dock personnel. (b) The ship's captain. (c) Both the same amount, because both sets of people were moving relative to each other. (d) We need to know how far away the star is. Answer: B

26-8. Which of the following will two observers in inertial reference frames always agree on? (Choose all that apply.)

(a) The time an event occurred. (b) The distance between two events. (c) The time interval between the occurence of two events. (d) The speed of light. (e) The validity of the laws of physics. (f) The simultaneity of two events. Answer: D,E

20-12. Two parallel wires are vertical. The one on the left carries a 10-A current upward. The other carries 5-A current downward. Compare the magnitude of the force that each wire exerts on the other.

(a) The wire on the left carries twice as much current, so it exerts twice the force on the right wire as the right one exerts on the left one. (b) The wire on the left exerts a smaller force. It creates a magnetic field twice that due to the wire on the right; and therefore has less energy to cause a force on the wire on the right. (c) The two wires exert the same force on each other. (d) Not enough information; we need the length of the wire. Answer: C

24-4. A double-slit experiment yields an interference pattern due to the path length difference from light traveling through one slit versus the other. Why does a single slit show a diffraction pattern?

(a) There is a path length difference from waves originating at different parts of the slit. (b) The wavelength of the light is shorter than the slit. (c) The light passing through the slit interferes with light that does not pass through. (d) The single slit must have something in the middle of it, causing it to act like a double slit. Answer: A

20-8. A wire carries a current directly away from you. Which way do the magnetic field lines produced by this wire point?

(a) They point parallel to the wire in the direction of the current. (b) They point parallel to the wire opposite the direction of the current. (c) They point toward the wire. (d) They point away from the wire. (e) They make circles around the wire. Answer: A

21-13. Which of the following statements about transformers is false?

(a) Transformers work using ac current or dc current. (b) If the current in the secondary is higher, the voltage is lower. (c) If the voltage in the secondary is higher, the current is lower. (d) If no flux is lost, the product of the voltage and the current is the same in the primary and secondary coils. Answer: A

22-1. In a vacuum, what is the difference between a radio wave and an X-ray?

(a) Wavelength. (b) Frequency. (c) Speed. Answer: A,B

23-12. You cover half of a lens that is forming an image on a screen. Compare what happens when you cover the top half of the lens versus the bottom half.

(a) When you cover the top half of the lens, the top half of the image disappears; when you cover the bottom half of the lens, the bottom half of the image disappears. (b) When you cover the top half of the lens, the bottom half of the image disappears; when you cover the bottom half of the lens, the top half of the image disappears. (c) The image becomes half as bright in both cases. (d) Nothing happens in either case. (e) The image disappears in both cases. Answer: C

24-5. If you hold two fingers very close together and look at a bright light, you see lines between the fingers. What is happening?

(a) You are holding your fingers too close to your eye to be able to focus on it. (b) You are seeing a diffraction pattern. (c) This is a quantum-mechanical tunneling effect. (d) The brightness of the light is overwhelming your eye. Answer: B

21-15. The alternating electric current at a wall outlet is most commonly produced by

(a) a connection to rechargeable batteries. (b) a rotating coil that is immersed in a magnetic field. (c) accelerating electrons between oppositely charged capacitor plates. (d) using an electric motor. (e) alternately heating and cooling a wire. Answer: B

22-6. If electrons in a wire vibrate up and down 1000 times per second, they will create an electromagnetic wave having

(a) a wavelength of 1000 m. (b) a frequency of 1000 Hz. (c) a speed of 1000 m/s. (d) an amplitude of 1000 m. Answer: B

25-3. When a nearsighted person looks at a distant object through her glasses, the image produced by the glasses should be

(a) about 25 cm from her eye. (b) at her eye's far point. (c) at her eye's near point. (d) at the far point for a normal eye. Answer: B

24-6. Light passes through a slit that is about 5 × 10-3 m high and 5 × 10-7 m wide. The central bright light visible on a distant screen will be

(a) about 5 × 10-3 m high and about 5 × 10-7 m wide. (b) about 5 × 10-3 m high and wider than 5 × 10-7 m. (c) about 5 × 10-3 m high and narrower than 5 × 10-7 m. (d) taller than 5 × 10-3 m high and wider than 5 × 10-7 m. (e) taller than 5 × 10-3 m high and about 5 × 10-7 m wide. Answer: B

26-5. An Earth observer notes that clocks on a passing spacecraft run slowly. The person on the spacecraft

(a) agrees her clocks move slower than those on Earth. (b) feels normal, and her heartbeat and eating habits are normal. (c) observes that Earth clocks are moving slowly. (d) The real time is in between the times measured by the two observers. (e) Both (a) and (b). (f) Both (b) and (c). Answer:F

25- 13. A converging lens, like the type used in a magnifying glass,

(a) always produces a magnified image (image taller than the object). (b) can also produce an image smaller than the object. (c) always produces an upright image. (d) can also produce an inverted image (upside down). (e) None of these statements are true. Answer: B,D

23-9. A converging lens, such as a typical magnifying glass,

(a) always produces a magnified image (taller than object). (b) always produces an image smaller than the object. (c) always produces an upright image. (d) always produces an inverted image (upside down). (e) None of these statements are true. answer: E

20-5. As a proton moves through space, it creates

(a) an electric field only. (b) a magnetic field only. (c) both an electric field and magnetic field. (d) nothing; the electric field and magnetic fields cancel each other out. Answer: C

25-1. The image of a nearby object formed by a camera lens is

(a) at the lens' focal point. (b) always blurred. (c) at the same location as the image of an object at infinity. (d) farther from the lens than the lens' focal point. Answer: D

21-12. A laptop computer's charger unit converts 120 V from a wall power outlet to the lower voltage required by the laptop. Inside the charger's plastic case is a diode or rectifier (discussed in Chapter 29) that changes ac to dc plus a

(a) battery. (b) motor. (c) generator. (d) transformer. (e) transmission line. Answer: D

18-1. When connected to a battery, a lightbulb glows brightly. If the battery is reversed and reconnected to the bulb, the bulb will glow

(a) brighter. (b) dimmer. (c) with the same brightness. (d) not at all. Answer: C

21-2. A wire loop moves at constant velocity without rotation through a constant magnetic field. The induced current in the loop will be

(a) clockwise. (b) counterclockwise. (c) zero. (d) We need to know the orientation of the loop relative to the magnetic field. Answer: C

24-8. Imagine holding a circular disk in a beam of monochromatic light (Fig. 24-56). If diffraction occurs at the edge of the disk, the center of the shadow is

(a) darker than the rest of the shadow. (b) a bright spot. (c) bright or dark, depending on the wavelength. (d) bright or dark, depending on the distance to the screen. Answer: B

16-6. As an object acquires a positive charge, its mass usually

(a) decreases. (b) increases. (c) stays the same. (d) becomes negative. Answer : A

23-4. When you look at a fish in a still stream from the bank, the fish appears shallower than it really is due to refraction. From directly above, it appears

(a) deeper than it really is. (b) at its actual depth. (c) shallower than its real depth. (d) It depends on your height above the water. Answer: C

23-6. To shoot a swimming fish with an intense light beam from a laser gun, you should aim

(a) directly at the image. (b) slightly above the image. (c) slightly below the image. Answer: A

16-10. To be safe during a lightning storm, it is best to be

(a) in the middle of a grassy meadow. (b) inside a metal car. (c) next to a tall tree in a forest. (d) inside a wooden building. (e) on a metal observation tower. Answer: B

19-8. When the switch shown in Fig. 19-45 is closed, what will happen to the voltage across resistor R1? It will

(a) increase. (b) decrease. (c) stay the same. Answer: A

17-9. A battery establishes a voltage V on a parallel-plate capacitor. After the battery is disconnected, the distance between the plates is doubled without loss of charge. Accordingly, the capacitance ___________ and the voltage between the plates ___________.

(a) increases; decreases. (b) decreases; increases. (c) increases; increases. (d) decreases; decreases. (e) stays the same; stays the same. Answer: B

25-5. The image produced on the retina of the eye is _____ compared to the object being viewed.

(a) inverted. (b) upright. (c) sideways. (d) enlarged. Answer: A

20-7. Which of the following statements is false? The magnetic field of a current-carrying wire

(a) is directed circularly around the wire. (b) decreases inversely with the distance from the wire. (c) exists only if the current in the wire is changing. (d) depends on the magnitude of the current. Answer: B

23-11. A lens can be characterized by its power, which

(a) is the same as the magnification. (b) tells how much light the lens can focus. (c) depends on where the object is located. (d) is the reciprocal of the focal length. Answer:D

23-14. As an object moves from just outside the focal point of a converging lens to just inside it, the image goes from _____and _____ to ____ and ____.

(a) large; inverted; large; upright. (b) large; upright; large; inverted. (c) small; inverted; small; upright. (d) small; upright; small; inverted. Answer: A

25-8. It would be impossible to build a microscope that could use visible light to see the molecular structure of a crystal because.

(a) lenses with enough magnification cannot be made. (b) lenses cannot be ground with fine enough precision. (c) lenses cannot be placed in the correct place with enough precision. (d) diffraction limits the resolving power to about the size of the wavelength of the light used. (e) More than one of the above is correct. Answer: D

25-7. When you closely examine an object through a magnifying glass, the magnifying glass

(a) makes the object bigger. (b) makes the object appear closer than it actually is. (c) makes the object appear farther than it actually is. (d) causes additional light rays to be emitted by the object. Answer: C

22-2. The radius of an atom is on the order of 10-10 m. In comparison, the wavelength of visible light is

(a) much smaller. (b) about the same size. (c) much larger. Answer: C

23- 5. Parallel light rays cross interfaces from medium 1 into medium 2 and then into medium 3 as shown in Fig. 23-51. What can we say about the relative sizes of the indices of refraction of these media?

(a) n1 > n2 > n3. (b) n3 > n2 > n1. (c) n2 > n3 > n1. (d) n1 > n3 > n2. (e) n2 > n1 > n3. (f) None of the above. Answer : E

25-4. If the distance from your eye's lens to the retina is shorter than for a normal eye, you will struggle to see objects that are

(a) nearby. (b) far away. (c) colorful. (d) moving fast. Answer: A

26-7. Relativistic formulas for time dilation, length contraction, and mass are valid

(a) only for speeds less than 0.10c. (b) only for speeds greater than 0.10c. (c) only for speeds very close to c. (d) for all speeds. Answer: D

23-10. Virtual images can be formed by

(a) only mirrors. (b) only lenses. (c) only plane mirrors. (d) only curved mirrors or lenses. (e) plane and curved mirrors, and lenses. Answer: E

20-10. For a charged particle, a constant magnetic field can be used to change

(a) only the direction of the particle's velocity. (b) only the magnitude of the particle's velocity. (c) both the magnitude and direction of the particle's velocity. (d) None of the above. Answer: A

16-13. A small metal ball hangs from the ceiling by an insulating thread. The ball is attracted to a positively charged rod held near the ball. The charge of the ball must be

(a) positive. (b) negative. (c) neutral. (d) positive or neutral. (e) negative or neutral. Answer: E

22-7. If the Earth-Sun distance were doubled, the intensity of radiation from the Sun that reaches the Earth's surface would

(a) quadruple. (b) double. (c) drop to 1/2. (d) drop to 1/4 Answer: D

23-2. When the reflection of an object is seen in a flat mirror, the image is

(a) real and upright. (b) real and inverted. (c) virtual and upright. (d) virtual and inverted. Answer:C

24-1. Light passing through a double-slit arrangement is viewed on a distant screen. The interference pattern observed on the screen would have the widest spaced fringes for the case of

(a) red light and a small slit spacing. (b) blue light and a small slit spacing. (c) red light and a large slit spacing. (d) blue light and a large slit spacing. Answer: A

20-4. When a charged particle moves parallel to the direction of a magnetic field, the particle travels in a

(a) straight line. (b) circular path. (c) helical path. (d) hysteresis loop. Answer: A

17-2. Two identical positive charges are placed near each other. At the point halfway between the two charges,

(a) the electric field is zero and the potential is positive. (b) the electric field is zero and the potential is zero. (c) the electric field is not zero and the potential is positive. (d) the electric field is not zero and the potential is zero. (e) None of these statements is true. Answer:A

16-9. We are usually not aware of the electric force acting between two everyday objects because

(a) the electric force is one of the weakest forces in nature. (b) the electric force is due to microscopic-sized particles such as electrons and protons. (c) the electric force is invisible. (d) most everyday objects have as many plus charges as minus charges. Answer: D

18-11. When a light switch is turned on, the light comes on immediately because

(a) the electrons coming from the power source move through the initially empty wires very fast. (b) the electrons already in the wire are instantly "pushed" by a voltage difference. (c) the lightbulb may be old with low resistance. It would take longer if the bulb were new and had high resistance. (d) the electricity bill is paid. The electric company can make it take longer when the bill is unpaid. Answer: B

24-3. The colors in a rainbow are caused by

(a) the interaction of the light reflected from different raindrops. (b) different amounts of absorption for light of different colors by the water in the raindrops. (c) different amounts of refraction for light of different colors by the water in the raindrops. (d) the downward motion of the raindrops. Answer: C

24-7. Blue light of wavelength A passes through a single slit of width d and forms a diffraction pattern on a screen. If we replace the blue light by red light of wavelength 2, we can retain the original diffraction pattern if we change the slit width

(a) to d/4. (b) to d/2. (c) not at all. (d) to 2d. (e) to 4d. Answer: D

25-10. The resolving power of a microscope is greatest when the object being observed is illuminated by

(a) ultraviolet light. (b) infrared light. (c) visible light. (d) radio waves. Answer: A

21-1. A coil rests in the plane of the page while a magnetic field is directed into the page. A clockwise current is induced

(a) when the magnetic field gets stronger. (b) when the size of the coil decreases. (c) when the coil is moved sideways across the page. (d) when the magnetic field is tilted so it is no longer perpendicular to the page. Answer: B,D,

21-8. Two separate but nearby coils are mounted along the same axis. A power supply controls the flow of current in the first coil, and thus the magnetic field it produces. The second coil is connected only to an ammeter. The ammeter will indicate that a current is flowing in the second coil

(a) whenever a current flows in the first coil. (b) only when a steady current flows in the first coil. (c) only when the current in the first coil changes. (d) only if the second coil is connected to the power supply by rewiring it to be in series with the first coil. Answer: C

23-1. Suppose you are standing about 3 m in front of a mirror. You can see yourself just from the top of your head to your waist, where the bottom of the mirror cuts off the rest of your image. If you walk one step closer to the mirror

(a) you will not be able to see any more of your image. (b) you will be able to see more of your image, below your waist. (c) you will see less of your image, with the cutoff rising to be above your waist. Answer: A

16-2. Swap the positions of Q1 and Q2 of MisConceptual Question 1. Which of the following is true of the force on Q1 due to Q2?

(a)It does not change. (b)It changes from attractive to repulsive. (c)It changes from repulsive to attractive. (d)It changes from the +x direction to the -x direction. (e) It changes from the -x direction to the +x direction. Answer: D