sample exam 4
Student: ___________________________________________________________________________
1. To best excite the fundamental frequency of a guitar string, pluck it 
 
A. near one end.
B. over the sound hole.
C. with a pick.
D. in the middle.
 
2. Which of these lists is in order of increasing wavelength? 
 
A. First harmonic, second harmonic, third harmonic.
B. Second harmonic, third harmonic, fourth harmonic.
C. First harmonic, second harmonic, fundamental.
D. Third harmonic, second harmonic, first harmonic.
 
3. When a wave reflects from a stationary boundary, 
 
A. the frequency decreases.
B. the frequency is unchanged.
C. the frequency increases.
 
4. Suppose an audible sound wave were being produced at a frequency of 800 cycles per second. If the amplitude were doubled, the sound would become 
 
A. louder.
B. lower in pitch.
C. higher in pitch.
D. softer.
 
5. Imagine you are holding a long rope under tension attached to a distant support. You can generate periodic waves by shaking the end up and down. Changing which of the following will least affect the velocity of waves along the string? 
 
A. frequency
B. tension
C. mass per unit length of rope
D. None of these affect the wave speed.
 
6. Suppose the velocity of waves on a particular rope under a tension of 10 N is 12 m/s. If the tension is increased fourfold to 40 N what will be the new velocity of waves on the rope? 
 
A. 48 m/s.
B. 24 m/s.
C. 18 m/s.
D. 12 m/s.
E. 6 m/s.
 
7. Consider possible standing wave patterns for a string fastened at each end. Discussion in the text shows that there is a 
 
A. minimum possible wavelength.
B. maximum possible frequency.
C. maximum possible wavelength.
D. maximum possible amplitude.
 
8.  The speed of electromagnetic waves in air is 3.0  108 m/s. What is the wavelength of FM radio waves having a frequency of 1.0  108 Hz?  
 
A.  0.333 m 
B.  1.0 m 
C.  3.0 m 
D.  6.0 m 
E.  10 m 
 
9. In Young's double-slit experiment, light was first passed through a narrow single slit before going on to the double-slits. The reason for the first slit was 
 
A. to ensure a constant phase relationship between the interfering light waves.
B. to reduce the brightness of the light so the interference pattern could be seen.
C. to polarize the light.
D. to screen out all wavelengths except those in the visible light spectrum.
 
10. For visible light, which property of visible electromagnetic waves changes with color? 
 
A. Amplitude
B. Frequency
C. Wavelength
D. Amplitude and frequency
E. Frequency and wavelength
 
11. The wavelength of red light is ______ that of a green light. 
 
A. greater than
B. less than
C. same as
D. greater, same or less, depending on a source of light
 
12. Electromagnetic waves that travel through the air are 
 
A. transverse waves.
B. longitudinal waves.
C. a 50/50 combination of transverse and longitudinal waves.
D. mostly transverse with small admixture of longitudinal.
E. mostly longitudinal with small admixture of transverse.
 
13. The evening sunsets are reddish orange because the atmosphere 
 
A. is most efficient at scattering red light.
B. absorbs blue light.
C. is more efficient at scattering blue light.
D. absorbs the red light.
E. contains small amounts of red dust that give the air its red color.
 
14. EM waves tend to be scattered the most by an object that is 
 
A. magnetic.
B. a liquid.
C. conducting.
D. about the same size as the wave.
E. reflective.
 
15. A common property of all waves is the relationship between the speed (v), the wavelength () and the frequency of the wave (f). The correct equation for this relationship is 
 
A. f = v.
B.  = vf.
C. v = f.
D. v = f / .
 
16. A beam of orange light illuminates two slits that are closely spaced. The resulting intensity pattern is a series of bright and dark fringes. What happens to the intensity pattern if we now change to blue light? 
 
A. Nothing changes.
B. The series of bright and dark fringes changes to circular fringes.
C. The series of bright and dark fringes spreads out.
D. The series of bright and dark fringes gets closer together.
E. The series of bright and dark fringes disappears.
 
17. A piece of ordinary glass transmits about 92% of the visible light incident on the glass. The transmittance of the glass can be increased by 
 
A. increasing the intensity of the incident light.
B. applying an anti-reflective coating to both sides of the glass.
C. slightly tilting the glass with respect to the light beam.
D. making the glass thicker.
 
18. The diffraction of light by the iris of the eye limits 
 
A. the ability of our eyes to resolve very fine details.
B. the color response of our eyes.
C. our ability to see in the dark.
D. our peripheral vision.
 
19. A beam of "unpolarized" light 
 
A. can be polarized by reflecting it from a flat surface.
B. has a polarization direction that is constantly rotating.
C. does not have any polarized waves.
D. contains a single light wave with a fixed polarization direction.
 
20. Polaroid sunglasses are designed to transmit primarily 
 
A. horizontally polarized light.
B. vertically polarized light.
C. longitudinal light waves.
D. refracted waves.
E. light other than blue.
 
21. A converging lens 
 
A. always has a real image.
B. refracts all light towards the focal point.
C. always has two curved surfaces.
D. is thicker in the center than the edges.
 
22. Which of the following lenses is a diverging lens?

A. A
B. B
C. C
D. D
 
23. Light from the sun passes through a converging lens and forms an image at 
 
A. infinity.
B. the focal point.
C. the center of the lens.
D. the center of curvature of the lens.
 
24. The focal length of a glass lens depends on 
 
A. the curvature of the surface of the lens.
B. the index of refraction of the glass.
C. the intensity of the light passing through the lens.
D. both the curvature of the surface of the lens and the index of refraction of the glass.
E. both the index of refraction of the glass and the intensity of the light passing through the lens.
 
25. The rear view mirror of an auto bears the legend "Objects in mirror are closer than they appear". This mirror is a ______ mirror. 
 
A. concave
B. convex
C. converging
D. plane
 
26. A rainbow shows separate colors of the spectrum because, at raindrop surfaces, 
 
A. red light is bent more than green light.
B. blue light is bent more than red light.
C. green light is bent more than blue light.
D. all colors are bent the same hence the separation.
 
27. Convex (converging) lenses are worn by 
 
A. a farsighted person to make rays from a distant object diverge more strongly.
B. a farsighted person to make rays from a nearby object diverge less strongly.
C. a nearsighted person to make rays from a distant object diverge more strongly.
D. a nearsighted person to make rays from a nearby object diverge less strongly.
 
28. Rays from a distant object do not diverge enough for a nearsighted person to focus; this can be corrected with a 
 
A. converging or positive lens.
B. converging or negative lens.
C. diverging or positive lens.
D. diverging or negative lens.
 
29. A fish looks up through the smooth surface of the water at a bear directly above it. To the fish, the bear appears to be 
 
A. further away than it really is.
B. closer to the point directly above the fish than it really is.
C. exactly where it really is.
D. the bear cannot be seen by the fish, due to total internal reflection.
 
30. A ray emerges from water (n = 1.33) into air. The light ray will 
 
A. emerge in air at the same angle as in the water.
B. bend toward the normal on the air side.
C. bend away from the normal on the air side.
 
31. A ray of light traveling in a calm pond strikes the surface at an angle of incidence which is 5 less than the critical angle. This ray will 
 
A. be refracted away from the normal to the surface in the air.
B. be refracted toward the normal to the surface in the air.
C. undergo total internal reflection and not enter the air at all.
 
32. The image of an object placed 20 cm in front of a concave mirror of focal length 10 cm will be 
 
A. real and inverted.
B. real and erect.
C. virtual and inverted.
D. virtual and erect.
 
33. A horizontally moving charge enters a magnetic field that points up. The magnetic force pushes the charge to the right of its original path when viewed from the perspective of the charge. What is the sign of the charge? 
 
A. negative
B. positive
C. Not enough information to answer.
 
34. Which of these will always produce a magnetic field? 
 
A. a negative charge at rest
B. a positive charge at rest
C. another magnetic field
D. a moving charge
 
35. A magnetic compass points towards the north geographic pole of the Earth because 
 
A. all magnetic poles, north or south, point that way due to the spin of the Earth.
B. there is a north magnetic pole near the north geographic pole.
C. there is a south magnetic pole near the north geographic pole.
D. the static electricity in the atmosphere causes the alignment of the compass.
 
36. Which of the following cannot induce a voltage in a loop of wire? 
 
A. Expanding or contracting the loop in a region where there is no magnetic field.
B. Moving the loop near a magnet.
C. Moving a magnet near the loop
D. Changing the current in a nearby loop.
 
37. A transformer is used to either increase or decrease the voltage in an AC circuit. When the output voltage is greater than the input voltage of a transformer then 
 
A. the power output is smaller than the power input.
B. the power output is the same as the power input.
C. the power output is larger than the power input.
D. the power output depends on the ratio of turns in the primary and secondary.
 
38. The scientist credited with discovering that electric currents produce magnetic fields was 
 
A. Faraday.
B. Oersted.
C. Ampere.
D. Coulomb.
E. Tesla.
 
39. Two long bar magnets are aligned so that north poles face each other. The magnets are separated by 1 cm, and a repulsive force between the north poles is 0.10 N. When the separation is increased to 2 cm the force will be 
 
A. 0.10 N.
B. 0.050 N.
C. 0.025 N.
D. 0.20 N.
E. 0.40 N.
 
40. Two current-carrying wires are parallel to one another and separated by 1 cm. If the distance between them is increased to 2 cm the new force will be what factor times the original force? 
 
A. 4
B. 2
C. 1
D. ½
E. ¼
 
41. A transformer is to be used to step up voltage from an alternating current source from 110 V to 660 V. If the primary has 120 turns, then the number of turns in the secondary is 
 
A. 20.
B. 660.
C. 720.
D. 4320.
E. 6600.
 
42. The period of a sound wave is the 
 
A. end of the wave.
B. decade in which it is produced.
C. inverse of its frequency.
D. None of these.
 
43. Two musical strings have the same length and tension, but string A has one fourth the mass of string B. The speed of a wave on string A is 
 
A. one fourth the speed of a wave on string B.
B. one half the speed of a wave on string B.
C. twice the speed of a wave on string B.
D. four times the speed of a wave on string B.
E. the same as the speed of a wave on string B.
 
44. An organ pipe of length 3.0 m has one end closed. The two longest possible wavelengths for standing waves inside the pipe are 
 
A. 6 m and 3 m.
B. 12 m and 6 m.
C. 12 m and 4 m.
D. 9 m and 6 m.
E. 3 m and 1.5 m.
 
45. A string is held taut between two supports 4.0 m apart. The two longest possible wavelengths for standing waves are 
 
A. 4 m and 2 m.
B. 6 m and 3 m.
C. 8 m and 4 m.
D. 16 m and 5.3 m.
 
46. The current (measured in Amperes) in a circuit is 
 
A. the amount of charge (measured in Coulombs) that passes a point (in the circuit) in 1 second.
B. the amount of the total energy carried by 1 Coulomb of charge.
C. the total number of electrons in the circuit.
D. never lethal if the current is due to positive charges.
 
47. The resistance of a circuit element is a measure of 
 
A. the total energy of the charges in the circuit element.
B. the amount of work that an electron can perform.
C. the ratio of the voltage difference between element ends to the current in the element.
D. the size of the circuit.
 
48. A certain kind of light bulb carries 0.5 amperes of current when connected to a 120 Volt AC circuit. What is its power rating? 
 
A. 60 W
B. 75 W
C. 100 W
D. 240 W
 
49. Two light bulbs are installed in two sockets connected in parallel and power is then applied to the combination so that both bulbs light. If one of the bulbs is then removed from its socket, the other one will 
 
A. get brighter.
B. remain equally bright.
C. get dimmer.
D. go out.
 
50. What is the best way to ensure that a 40 watt bulb and a 60 watt bulb have the same 
current within them? 
 
A. Connect the bulbs in series with the power supply, like this:

B. Connect the bulbs in parallel with the power supply, like this:

C. Separately connect the bulbs to two batteries having the same voltage.
D. Can't be done: different wattage bulbs must always have different currents.
 
51. An ohm is equal to which of these? 
 
A. a volt
B. a coulomb per second
C. a volt per ampere
D. an ampere per second
 
52. A 6 ohm resistor and a 12 ohm resistor are connected in series in a circuit with a 6.0 volt battery. Assuming negligible internal resistance in the battery, the current in the 12 ohm resistor will be 
 
A. 0.33 A.
B. 0.5 A.
C. 1.0 A.
D. 12 A.
E. 36 A.
 
53. A 12 ohm resistor and a 24 ohm resistor are connected in parallel across a 6.0 V battery. The correct statement from the following is 
 
A. the current is the same in each resistor.
B. the power dissipated is the same in each resistor.
C. the voltage difference between the ends of each resistor is the same.
D. the larger current is in the larger resistor.
 
54. A heater is rated to dissipate 1800 W when connected to a 120 V source. The current drawn by the device is 
 
A. 1800 A.
B. 120 A.
C. 30 A.
D. 15 A.
E. 0.067 A.
 
55. The alternating current in wide use in homes in North America is 60 cycles per second, or 60 Hz. How many times per minute does this current reverse its direction of travel? 
 
A. 7200 times
B. 3600 times
C. 120 times
D. 60 times
E. None of these.

ANSWERS

1.	D     46.A 47.C 48.A 49.B50.A51.C 52.A 53.C 54.D 55.C
2.	D
3.	B
4.	A
5.	A       1. 5m,8Hz,14Hz  2.  300mm,-2,real,inverted    3.  4MV,10turns
6.	B
7.	C
8.	C
9.	A
10.	E
11.	A
12.	A
13.	C
14.	D
15.	C
16.	D
17.	B
18.	A
19.	A
20.	B
21.	D
22.	A
23.	B
24.	D
25.	B
26.	B
27.	B
28.	D
29.	A
30.	C
31.	A
32.	A
33.	B
34.	D
35.	C
36.	A
37.	B
38.	B
39.	C
40.	D
41.	C
42.	C
43.	C
44.	C
45.	C

!.   A 10m string attached firmly at both end is vibrating in its 4’th harmonic.    The speed of the mechanical wave is 40m/s.  Calculate the wavelength and the frequency.   Calculate the frequency of the 7’th harmonic.

2. A thin converging lens has a focal length of 100mm.  An object is placed 150 mm in front of the lens.  Calculate the image distance and the magnification.  Is the image virtual or real, erect or inverted?

3.  A generator rotates such that the flux changes from -10,000V-s to 10,000Vs every 0.005s.   Calculate the voltage difference generated.   If you wished to step down this voltage to 20KV and had 2000 turns on the primary, how many turns should there be on the secondary?