Waves, Particles, and Time Physics Practice Test
A good score is at least 37 correct. Answers are in given at the end. It is best to have a friend check your score the first time so that you won’t memorize the answers if you want to take the test again.
1. A wave has a frequency of 10 5 Hz. What is its period in microseconds?
(a) 10 −5
(b) 10 −2
(e) It depends on the speed of propagation.
2. A cassegrain reflector
(a) has a concave objective mirror and a flat secondary mirror.
(b) has a concave objective mirror and a convex secondary mirror.
(c) has a longer tube than an equivalent Newtonian reflector.
(d) suffers from lens sag if the diameter of the objective is too large.
(e) has the eyepiece mounted in the side of the tube.
3. Localized doses of radiation are sometimes used to
(a) control insects.
(b) improve female fertility.
(c) treat cataracts.
(d) treat cancerous growths.
(e) alleviate nausea.
4. Which of the following statements is false?
(a) A convex lens can bring parallel light rays to a focus.
(b) A concave mirror can collimate light rays from a point source.
(c) A convex mirror can be used as the main objective in a reflecting telescope.
(d) A concave lens makes close-up objects appear smaller.
(e) A convex lens can be used as the main objective in a refracting telescope.
5. Two waves mix together. Their frequencies are 5.00 MHz and 500 kHz, respectively. Which of the following is a beat frequency resulting from the heterodyning of these two signals?
(a) 2.50 MHz
(b) 2.50 GHz
(c) 10.0 MHz
(d) 4.50 MHz
(e) None of the above
6. Regardless of whether a reference frame is accelerating or not, light rays always
(a) travel in straight lines.
(b) follow the shortest possible path between two points in space.
(c) travel in curved paths.
(d) are repelled by gravitational fields.
(e) travel fastest in the direction of motion.
7. Suppose that a sample of a substance contains a huge number of radioactive atoms. You measure the length of time required for 10,000 of them to degenerate and then average all the results. The average decay time thus derived is called the
(b) mean life.
(c) decay life.
(d) ionizing life.
(e) degeneration life.
8. When light from the Sun shines on a spherical reflective object such as a steel ball bearing, the reflected rays
(a) are all parallel.
(d) focus to a point hot enough to start fires.
(e) behave unpredictably.
9. Imagine that a space ship whizzes by so fast that clocks on board seem, as seen from our point of view on Earth, to be running at one-third their normal speed. Suppose that you mass 60 kg on Earth and have a friend riding on the ship who also masses 60 kg on Earth. If your friend measures her mass while traveling on the ship, what will she observe it to be?
(a) 20 kg
(b) 60 kg
(c) 180 kg
(d) 540 kg
(e) It cannot be determined without more information.
10. Electromagnetic (EM) waves at radio frequencies
(a) are visible to the unaided eye.
(b) are a form of ionizing radiation that can cause genetic mutations.
(c) can propagate long distances through the air.
(d) are completely blocked by the atmosphere.
(e) produce curvature of space-time.
11. Which of the following statements is false?
(a) The visible-light range is a small part of the EM spectrum.
(b) Gamma rays have high penetrating power.
(c) Extremely-low-frequency (ELF) radiation is a form of radioactivity.
(d) Microwaves are longer than infrared (IR) waves.
(e) X-rays are shorter than visible-light waves.
12. In a compound microscope,
(a) the objective is a convex lens and the eyepiece is a concave lens.
(b) both the objective and the eyepiece are concave lenses.
(c) the objective is a concave mirror and the eyepiece is a convex lens.
(d) the eyepiece has a longer focal length than the objective.
(e) the eyepiece has a shorter focal length than the objective.
13. Carbon dating is commonly used to estimate
(a) the size of the universe.
(b) the temperature on the surface of the Sun.
(c) the rate at which the ozone layer is deteriorating.
(d) the altitude of the ionosphere.
(e) none of the above.
14. Fill in the blank in the following sentence: “When a space ship moves at a speed approaching the speed of light relative to an observer, that observer will see a clock on the ship appear to________.”
(a) run too fast
(c) run too slowly
(d) run infinitely fast
(e) run at normal speed
15. The so-called double-slit experiment demonstrates that
(a) sound waves can turn corners.
(b) electrons and positrons have opposite electric charge.
(c) visible light has wavelike properties.
(d) matter consists mostly of empty space.
(e) electromagnetic fields can travel through a vacuum.
16. Suppose that a space ship whizzes by so fast that clocks on board seem, as seen from our point of view, to be running at half speed. If the rest mass of the ship is 50 metric tons, what will be the mass of the ship from our point of view as it whizzes by?
(a) 25 metric tons
(b) 50 metric tons
(c) 100 metric tons
(d) 400 metric tons
(e) It cannot be determined without more information.
17. An EM field has a wavelength of 120 m. This is
(a) an ELF field.
(b) a radio wave.
(c) microwave energy.
(d) infrared energy.
(e) x-ray energy.
18. Time travel into the future might be possible by taking advantage of
(a) relativistic time dilation.
(b) relativistic mass distortion.
(c) relativistic spatial distortion.
(d) the gravitational pull of the Earth.
(e) nothing! Time travel into the future is theoretically impossible.
19. Which of the following statements is false?
(a) A glass prism bends green light more than it bends orange light.
(b) The focal length of a simple glass convex lens is shorter for green light than for orange light.
(c) Dispersion occurs when white light passes through a simple glass lens.
(d) The index of refraction of glass depends on the color of the light shining through it.
(e) All of the above statements are true.
20. All waves, no matter what the medium, have three distinct properties that depend on each other. These three properties are
(a) frequency, wavelength, and propagation speed.
(b) frequency, amplitude, and propagation speed.
(c) amplitude, waveform, and period.
(d) wavelength, amplitude, and period.
(e) waveform, propagation speed, and amplitude.
21. The maximum diameter of a refracting telescope is limited, in practice, by
(a) lens sag.
(b) spherical aberration.
(c) paraboloidal aberration.
(d) focal length.
22. Infrared radiation at low or moderate intensity
(a) can be felt as heat or warmth on the skin.
(b) is reflected by the Earth’s ionosphere.
(c) appears red or orange in color.
(d) has extreme penetrating power.
(e) can cause slow radioactive decay.
23. Suppose that two superaccurate atomic clocks, called clock A and clock B , are synchronized on Earth so that they agree exactly. Now imagine that clock B is placed aboard a space vessel and sent to Mars and back. The clock readings are compared after the ship returns. What do we find?
(a) Clocks A and B still agree precisely.
(b) Clock A is behind clock B .
(c) Clock A is ahead of clock B .
(d) Any of the above, depending on the extent to which the ship accelerated during its journey.
(e) None of the above.
24. Fill in the blank in the following sentence: “As the focal length of the objective lens in a compound microscope is reduced, and if all other factors remain constant, __________.”
(a) the magnification decreases
(b) the field of view increases
(c) the resolution decreases
(d) the magnification increases
(e) nothing changes
25. Suppose that you tune your car radio to a station in the AM broadcast band and you can hear that station even when driving through a valley or ravine. This effect is caused by
(a) wave diffraction.
(c) total internal reflection.
(d) a manifestation of Snell’s law.
(e) Earth’s magnetic field.
26. Einstein’s principle of equivalence states that
(a) gravitational force is just like acceleration force.
(b) force equals mass times acceleration.
(c) the speed of light is constant, no matter what.
(d) the speed of light is the highest possible speed.
(e) the shortest distance between two points is a straight line.
27. Which of the following types (a, b, c, or d) of radiation is not ionizing?
(a) Extremely low frequency
(c) Gamma rays
(d) Primary cosmic particles
(e) All of the above types of radiation are ionizing.
28. A corpuscle of visible light is called
(a) a positron.
(b) an electron.
(c) a neutron.
(d) a photon.
(e) an illumitron.
29. Suppose that a certain material transmits light at a speed of 150,000 km/s. What is its index of refraction, accurate to three significant figures?
30. The Earth’s ionosphere
(a) blocks all radio waves coming from space.
(b) shields us from the Sun’s x-rays.
(c) can give rise to damaging ultraviolet (UV) radiation.
(d) exists in layers at various altitudes above the surface.
(e) disappears during the daytime.
31. Suppose that there are two sound waves traveling in the air, wave A and wave B . The frequency of wave A is 500 Hz. The frequency of wave B is 2,500 Hz. What can be said about these waves?
(a) Wave B travels five times as fast as wave A .
(b) Wave A travels five times as fast as wave B .
(c) The amplitude of wave B is five times the amplitude of wave A .
(d) The amplitude of wave A is five times the amplitude of wave B .
(e) The two waves are harmonically related.
32. Spatial distortion can be caused by all of the following except
(c) high relative speed.
(d) black holes.
(e) the solar wind.
33. Fill in the blank in the following statement to make it true: “The light from a point source can be________by a convex lens.”
34. High levels of UV radiation, either short term or long term, are known or believed to cause all the following except
(a) long-term suppression of the immune system in humans.
(b) fluorescence of certain materials.
(c) skin cancer.
(d) cataracts in the eyes.
(e) ozone depletion.
35. When Michelson and Morley measured the speed of light in various directions, they discovered that
(a) the speed of light is slowest in the direction in which the Earth travels through space.
(b) the speed of light is fastest in the direction in which the Earth travels through space.
(c) the Earth drags the luminiferous ether along with itself.
(d) the speed of light is the same in all directions.
(e) the speed of light cannot be accurately determined.
36. Which of the following statements is true for an EM wave in free space? Assume that propagation speed is expressed in meters per second, period is expressed in seconds, frequency is expressed in hertz, and wavelength is expressed in meters.
(a) Propagation speed is equal to frequency times wavelength.
(b) Propagation speed is equal to frequency divided by wavelength.
(c) Propagation speed is equal to frequency times period.
(d) Period is equal to propagation speed divided by wavelength.
(e) Frequency is equal to propagation speed times wavelength.
37. Suppose that the path of the light from a distant quasar passes by an extremely massive, dense, dark object that is closer to us. Multiple images of the quasar appear around the dark object. This is the result of
(a) time dilation.
(b) red shift.
(c) spatial curvature.
(d) spherical aberration.
(e) chromatic aberration.
38. The term auroral propagation refers to
(a) reflection of radio waves by the aurorae.
(b) the tendency for aurorae to occur after a solar flare.
(c) a tendency for the aurorae to occur near the geomagnetic poles.
(d) the strange movements commonly observed in the aurorae.
(e) effects of the aurorae on living tissue.
39. Imagine a solid sphere of glass that is perfectly transparent and perfectly uniform with a spherical hollow space in the exact center. Imagine a light bulb, call it lamp A , with a point-source filament located at the center of the spherical hollow space and therefore also at the center of the whole sphere of glass. Imagine a second light bulb in the open air, also with a point-source filament; call it lamp B . How do the rays of light from the two lamps compare in their behavior?
(a) The rays from both lamps radiate outward in straight lines and in exactly the same way.
(b) The rays from lamp A are reflected totally inside the cavity within the sphere of glass, but the rays from lamp B radiate outward in straight lines.
(c) The rays from lamp A converge to a point somewhere outside the sphere of glass, but the rays from lamp B radiate outward in straight lines.
(d) The rays from lamp A diverge more when they emerge from the sphere of glass compared with the rays from lamp B that do not have to pass through the glass.
(e) It is impossible to say without more information.
40. A cordless telephone is advertised as operating at a frequency of 900 MHz. This is the same as a frequency of
(a) 9.00 × 10 5 Hz.
(b) 0.900 GHz.
(c) 9.00 × 10 −4 GHz.
(d) 0.900 THz.
(e) 9.00 × 10 8 kHz.
41. A common source of ELF radiation is
(b) a light bulb.
(c) a wire carrying direct current.
(d) a solar cell.
(e) an electrical utility line.
42. In a compound microscope, the adverse effects of chromatic aberration can be practically eliminated by
(a) using a mirror for the objective rather than a lens.
(b) illuminating the specimen from behind.
(c) illuminating the specimen from in front.
(d) increasing the distance between the objective and the eyepiece.
(e) using monochromatic light to illuminate the specimen.
43. The occurrence of time dilation, as predicted by Einstein’s special theory of relativity, was demonstrated by
(a) placing atomic clocks in gravitational fields of various intensities.
(b) measuring the red shift of light as it passes near the Sun on its way to us from distant stars.
(c) observing the curvature of space in a fast-moving vessel.
(d) comparing the reading of an atomic clock on an aircraft with the reading of a similar clock on Earth.
(e) none of the above; it cannot be demonstrated at speeds attainable using present technology.
44. A wave that concentrates all its energy at a single frequency has a shape that can be described as
45. Relativistic spatial distortion, resulting from high relative velocity, occurs
(a) only at speeds faster than the speed of light.
(b) only when objects accelerate.
(c) only along the axis of relative motion.
(d) only for extremely dense or massive objects.
(e) only within black holes.
46. The depth of field in a compound microscope at high magnification
(a) is essentially infinite.
(b) is large, on the order of several kilometers.
(c) is small, on the order of a few micrometers.
(d) depends on the illumination level.
(e) depends on the type of eyepiece used.
47. Suppose that a light beam consists of photons, all of which contain the same amount of energy. If the frequency of the light waves is multiplied by 5 (so that it becomes UV), what will happen to the energy contained in each photon?
(a) It will not change.
(b) It will become 5 times as great.
(c) It will become 25 times as great.
(d) It will become as great.
(e) It will become as great.
48. A rising Moon sometimes appears reddish because
(a) red light is scattered by the atmosphere more than other light.
(b) red light is scattered by the atmosphere less than other light.
(c) dust in the air always has a reddish hue.
(d) atoms in the air are actually red.
(e) an optical illusion occurs.
49. A telescope can be made using
(a) a concave objective lens and a convex eyepiece lens.
(b) a convex objective lens and a concave eyepiece lens.
(c) a convex objective mirror and a concave eyepiece lens.
(d) a concave objective lens and a concave eyepiece lens.
(e) any of the above.
50. Suppose that there are two sound waves, wave A and wave B , traveling through the air. They have identical frequency, say, 800 Hz. Wave A is a square wave, and wave B is a sawtooth. What can be said about these waves?
(a) Waves A and B both concentrate all their energy at 800 Hz.
(b) Wave A has a different timbre than wave B .
(c) Waves A and B travel through the air at different speeds.
(d) Waves A and B have different amplitudes.
(e) Waves A and B have different wavelengths.
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