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Physics R: Form TR8.16A
Name ______________________________
TEST 8 REVIEW
Date _________________ Period _____
Test Review # 8
Optical Devices. Some common optical devices, devices that use mirrors and/or lenses, include microscopes, telescopes,
cameras, projectors, and lasers. Microscopes are used to magnify small objects. A compound microscope has two sets of
convex lenses, an eyepiece and an objective. The objective produces an enlarged, inverted, real image in the microscope tube.
The eyepiece magnifies the enlarged image further enlarging it. Telescopes are used to examine objects that are far away.
Telescopes need to have a large objective lens in order to collect as much light as possible so far away objects are bright
enough to be seen. There are two types of telescopes–a refracting telescope and a reflecting telescope. A refracting telescope
works the same way that a microscope works. A reflecting telescope has a concave mirror instead of a convex objective lens
to gather light. The concave mirror reflects light onto a secondary plane mirror. The secondary mirror reflects light through
the eyepiece which magnifies the image. Cameras focus an image on a light sensitive layer to take a photograph. A camera
uses a convex lens with a short focal length to focus an inverted, real image that is smaller than the object on the light
sensitive layer. For many cameras, diaphragm with a variable f-stop is used to control the exposure. A projector is used to
shine an image on a surface. A concave mirror reflects light from an intense source. A condenser consisting of two
planoconvex lenses directs light through a slide or movie frame to a projection lens. The projection lens focuses an image
on a screen. Lasers provide a high energy narrow beam of light. Most light beams spread out because they are composed of
different frequency waves that are out of phase with each other. The more a light beam spreads, the less energy is focused
on a given point. Lasers are monochromatic, so the waves stay in phase and they don’t spread. This makes the laser beam
narrower and higher energy.
Electromagnetic Waves. Electromagnetic waves are produced by charged particles in motion. They consist of two force
fields that enable them to exert forces on objects without touching them. Magnets are surrounded by a force field called a
magnetic field. A magnetic field exerts a force on other magnets and magnetic materials that cause them to line up along the
direction of the magnetic field. Charged particles are surrounded by a force field called an electric field. Electric fields exert
forces on other charged particles within the field. Opposite charges attract, while like charges repel.
Electromagnetic waves are produced by the vibrations or oscillations of charged particles. The frequency is the number
of times a particle vibrates per second. The vibrations produce a wave with a wavelength inversely proportional to the
frequency (one vibration = one wavelength). The wave moves away from the vibrating particle. The electric field moves away
in the same plane as the vibration. The magnetic field moves away at right angles to the plane of vibration. Energy carried
by an electromagnetic wave is called radiant energy. The energy of the wave is determined by the frequency. The speed of
all electromagnetic waves through space is about 300,000 km/s.
THE ELECTROMAGNETIC SPECTRUM. The electromagnetic spectrum is a wide range of electromagnetic waves with different
frequencies and wavelengths.
Radio waves are electromagnetic waves with wavelengths greater than about 0.001 m. They have the lowest energy and
frequency of all electromagnetic radiation. Radio waves include TV signals, and AM and FM radio signals. They are
produced in a broadcasting antenna by making electrons in the metal vibrate. These radio waves cause electrons in a receiving
antenna to vibrate, creating an alternating current that is used to produce a picture on a TV screen or sound from a loud
speaker. Microwaves are higher frequency radio waves with wavelengths between 0.3 m and 0.001 m. Microwaves warm
food in microwave ovens by making water molecules vibrate faster. They’re also used to transmit cell phone signals. Radar
is an acronym for RAdio Detecting And Ranging. Radar uses radio waves to detect objects by echolation. A radar station
sends out radio waves that bounce off an object. Electronic equipment measures the time it takes for the radio wave to reach
an object, be reflected, and return. The speed of the radio wave is used to calculate the distance. Because of the high speed
of the radio wave, the process takes only a fraction of a second.
Infrared waves are electromagnetic waves with wavelengths between 1,000 µm and 0.7 µm. They are emitted all objects,
and detected as heat. Most electromagnetic energy given off at room temperature is infrared radiation with a wavelength of
about 10 µm. Infrared detectors detect objects that are warmer or cooler than their surroundings. Satellites with infrared
detectors can be used for mapping forests, water, rocks, and soil. Forests and areas covered with vegetation tend to be cooler
than their surroundings. Night vision devices use infrared. Snakes such as pit vipers have a pit located between the nostril
and the eye that helps them hunt by detecting infrared.
Physics R: Form TR8.16A
TEST 8 REVIEW
Test Review 8
Page 2
Visible light consists of electromagnetic waves with wavelengths between 0.7 µm and 0.4 µm. Different colors have
different wavelengths. Red light has the longest wavelength and the lowest frequency. Blue light has the shortest wavelength
and the highest frequency. Most objects that you see do not give off visible light, but they reflect it. The most intense light
given off by the sun is visible light.
Ultraviolet radiation has electromagnetic waves with wavelengths between 0.4 µm and 0.01 µm. It has a shorter
wavelength, higher frequency, and more energy than visible light. Ultraviolet radiation can kill or damage cells. Exposure
over time can lead to early aging of the skin and to skin cancer. The body’s natural defense against ultraviolet radiation is
to tan. Ultraviolet enables humans to produce vitamin D. It is used to disinfect and sterilize equipment. Most UV light
arriving at the Earth is absorbed by the ozone in the upper atmosphere. The atmosphere also absorbs higher energy radiation
such as X-rays and gamma rays, but is transparent to visible light and radio waves, and partially transparent to infrared waves.
X-rays have a higher frequency than UV light, and gamma rays have a higher frequency than X-rays. As a result,
X-rays have higher energy than UV light and gamma rays have higher energy than X-rays. They both have a greater ability
to penetrate and damage cells than UV light with gamma rays being worst. X-rays are used to produce images on a film (an
X-ray) in order to detect injuries, and disease such as broken bones and cancer. X-rays pass easier through less dense tissues,
and are absorbed by bone. As a result, X-rays strike a film creating a shadow of denser tissue. CT scans are X-ray images
of the human body as if it had been sliced. Gamma rays can be used to kill cancerous tumors and bacteria in food.
Communication. Radio waves are used to send and receive information over long distances to radios, TVs, and telephones.
They pass through walls and windows easily, and do not interact with humans, so they are not dangerous.
Radio. Each radio station or channel broadcasts an assigned frequency carrier wave. The carrier wave is modified or
modulated through interference to carry information. In amplitude modulation (AM), the amplitude of the carrier wave is
changed to carry information. An AM receiver tunes to the frequency of the carrier wave. The varying amplitude creates an
electric current in the receiver antenna. A loudspeaker converts the current into sound. In frequency modulation (FM) the
frequency of the carrier wave is changed to carry information. An FM receiver has components that convert varying
frequencies into an electric current that the loudspeaker converts into sound.
Telephones. There are two main types of telephones: land-lines and remote phones. Land-lines produce an electrical signal
through a microphone in the mouthpiece. The signal is transmitted in several possible ways. It may go through wires, be
converted into radio waves or microwaves for transmission through the air, or converted to light for transmission through
fiber-optic cables. The signal to land-lines, which is received through the phone lines, is converted back to electric current. A
speaker in the earpiece converts the electric signal into sound. Remote phones include cordless phones, cell phones, and pagers.
An antenna in the cordless phone broadcasts to a base station which transmits and receives like a land-line phone. The base
station also broadcasts to the cordless phone. The base station cannot be more than 0.5 km away. Cell phones broadcast to and
receive from a base station or cell tower that is several kilometers or more away. The cell tower has a large antenna and may
communicate with other cell towers in the network. When a pager is dialed, a base station receives the signal. From there a signal
is sent to the pager.
Communication satellites. Communication satellites are used for long distance communication. Radio waves travel in
straight lines. The earth’s surface is curved and radio waves can’t curve around or pass through the earth. Radio signals can
be sent to satellites which can transmit to other satellites or to ground stations. Some satellites are geosynchronous, meaning
they move at the same rate as the earth spins so they remain above the same point on the ground. The Global Positioning
System (GPS) consists of several satellites and ground based stations or portable units with receivers. The GPS receiver
measures the time it takes for radio waves to travel from several satellites to the receiver. The receiver uses the information
to calculate its latitude, longitude, and elevation.
Physics R: Form TR8.16A
Test Review 8
TEST 8 REVIEW
Page 3
Calculating Joules. When you heat a solid, it’s temperature generally goes
Q = mCp ΔT
up. There is a relationship between heat and temperature, but they are not the
Q = heat (J)
m = mass in grams
same thing. It would take a lot more energy to heat up the ocean than to
ΔT = change in temperature [ΔT = Tf – Ti]
warm a cup of tea. The ocean has a larger mass. It has many more molecules
Tf = final temperature
to share energy with. Mass is not the only thing that influences the way the
Ti = starting temperature
temperature changes in response to heat. When the same sun beats down on Cp = 4.18 J/gEC for water
the beach, the sand gets a lot hotter than the water. Water has a higher heat
capacity than sand. The relationship between mass, temperature change,
Q
specific heat, and energy are shown to the right.
cp =
m∆ T
Specific Heat. Some substances are more resistant to temperature change
Q
=
joules;
m
=
mass
in grams
than others. They have a higher specific heat. The equation for determining
ΔT
=
change
in
temperature
[ΔT = Tf – Ti]
specific heat is shown to the right
T
=
final
temperature
(EC)
f
Refrigeration. Refrigeration is cooling something below the temperature
Ti = starting temperature (EC)
of the surroundings. Food snd drinks are kept cool in a refrigerator. A
cp = specific heat (J/gEC)
refrigerator works as follows: (1) Liquid coolant is forced through a pipe
towards the freezer; (2) The liquid passes through an expansion valve and
turns into a gas, causing it to cool; (3) The cold gas moves through the refrigerator pipes and absorbs energy from the food;
(4) The coolant is compressed and becomes warmer than room temperature; (5) The hot gas goes into the condenser coils
where it loses thermal energy to its surroundings; (6) The cycle repeats. An air conditioner works the same as a refrigerator.
A heat pump also works the same as a refrigerator, but coolant can move in either direction so it can cool or heat the inside.
TRANSFER OF THERMAL ENERGY: Energy always moves from warmer to cooler objects.
Conduction. Conduction is the transfer of heat from molecule to molecule through collisions. When high energy
molecules collide with low energy molecules, there is conservation of momentum. The higher energy molecules move away
slower, but the lower energy molecules move away faster. Solids and liquids are better conductors than gases because the
molecules are closer together.
Radiation. Radiation is the transfer of electromagnetic waves (light, radio waves, etc.) through empty space.
Electromagnetic waves can travel through space, but when they hit matter they are absorbed. Since energy is conserved, the
energy absorbed by the matter is not lost. Rather, it causes the particles to move faster. That is why you get hot if you wear
a dark outfit on a sunny day.
Answer the questions below by circling the number of the correct response.
1. The eyepiece of a compound microscope acts like a magnifying
glass for the image produced by the objective lens. The final image
you see by looking in the microscope must be: (1) real. (2) virtual.
(3) aberrated. (4) projected.
2. Which of the following does NOT use lenses? (1) microscope
(2) camera (3) projector (4) laser
3. A refracting telescope is different from a reflecting telescope in that
the objective of a reflecting telescope is a (1) lens, (2) concave
mirror, (3) convex mirror, (4) plane mirror.
4. A laser has a narrow high energy beam compared to other light
sources because it is (1) white light, (2) red light, (3) green light,
(4) monochromatic light.
5. Telescopes need a large objective lens in order to (1) have high
magnification, (2) gather a lot of light, (3) form a real image, (4) form
a virtual image.
6. A camera needs a convex lens with a short focal length in order to
produce a (1) tiny virtual image, (2) magnified virtual image, (3) tiny
real image, (4) magnified real image.
7. *What is a force field? (1) something that exerts forces on objects
without touching them (2) an electromagnetic wave (3) a mass
undergoing acceleration (4) a magnet.
8. How many force fields does an electromagnetic wave have? (1) 1
(2) 2 (3) 3 (4) 4
9. Which of the following transformations can occur in a radio antenna?
(1) radio waves to sound waves (2) radio waves to an electric signal
(3) radio waves to infrared waves (4) sound waves to radio waves
10. Which of the following is the speed of light in space? (1) 186,000
km/s (2) 300,000 km/s (3) 3,000,000 km/s (4) 30,000 km/s
Physics R: Form TR8.16A
TEST 8 REVIEW
11. Which of the following types of electromagnetic waves has the
lowest frequency? (1) infrared waves (2) visible light (3) radio
waves (4) gamma rays
12. Compared to an electric charge that is not moving, a moving electric
charge is surrounded by which of the following additional fields?
(1) magnetic (2) microwave (3) electric (4) gravitational
13. Most of the electromagnetic waves emitted by an object at room
temperature which of the following? (1) visible light (2) radio waves
(3) infrared waves (4) X–rays
14. Which of the following colors of visible light has the highest
frequency? (1) green (2) blue (3) yellow (4) red
15. Which type of electromagnetic waves are completely absorbed by
Earth's atmosphere?
(1) radio waves (2) infrared waves
(3) gamma rays (4) visible light
16. Sunburn is caused by excessive exposure to which of the following?
(1) ultraviolet waves (2) infrared waves (3) visible light (4) gamma
rays
Test Review 8
Page 4
22. Which of the following is NOT true about electromagnetic waves?
(1) They can travel through matter. (2) They move by transferring
matter. (3) They are produced by vibrating charges. (4) They can
travel through empty space.
23. Earth’s atmosphere is transparent to which type of electromagnetic
waves? (1) gamma rays (2) ultraviolet waves (3) infrared waves
(4) radio waves
24. *The temperatures of two glasses of water are 30°C and 0°C. Which
of the following is a correct statement about the two glasses of
water? (1) The cold water has a higher average kinetic energy.
(2) The warmer water has lower thermal energy. (3) The molecules
of the cold water move faster. (4) The molecules of the warmer
water have more kinetic energy.
25. When 84 joules of heat is added to 2.0 gram of water at 15EC, the
temperature of the water increases to (1) 5.0EC, (2) 15EC,
(3) 25EC, (4) 50. 0 C
26. How many joules of heat energy are released when 50 grams of
water are cooled from 70EC to 60EC? (1) 42 joules (2) 209 joules
(3) 2090 joules (4) 4,180 joules
17. How does the frequency of a gamma ray change as its wavelength
decreases? (1) It increases. (2) It decreases. (3) It doesn't
change. (4) The frequency depends on the speed.
27. The number of joules needed to raise the temperature of 10 grams
of' water from 20EC to 30EC is (1) 42, (2) 84, (3) 418, (4) 167
18. Which of the following types of electromagnetic waves has a
frequency greater than visible light? (1) infrared waves (2) radio
waves (3)ultraviolet waves (4)microwaves
28. A 5-gram sample of water is heated and the temperature rises from
10EC to 15EC. The total amount of heat energy absorbed by the
water is (1) 105 J, (2) 84 J, (3) 63 J, (4) 21 J
19. Which of the following types of electromagnetic waves enables your
body to produce vitamin D? (1) gamma rays (2) ultraviolet waves
(3) visible light (4) infrared waves
29. How many joules of heat energy are absorbed when 0.100 grams of
water is heated from 20EC to 30EC? (1) 4.18 J (2) 41.8 J (3) 418 J
(4) 0.42 J
20. Based on the
Electromagnetic Waves from the Sun
illustration to
the right, how
does the
i n t e n s ity o f
ultraviolet
waves emitted
by the Sun
change as the
wave-length of
the ultraviolet
waves decreases? (1) The intensity increases. (2) The intensity
decreases. (3) The intensity doesn't change. (4) The intensity
increases, then decreases.
30. How many joules of heat are needed to raise the temperature of 5.
grams of water from 10.0EC to 12.0EC? (1) 42 J (2) 105J
(3) 210. J (4) 168 J
31. When 5 grams of water at 20EC absorbs 10 joules of heat, the
temperature of the water will be increased by a total of (1) 0. 5 CE
(2) 2 CE (3) 10 CE (4) 50 CE
21. The color of visible light waves depends on which of the following
wave properties? (1) wavelength (2) amplitude (3) direction
(4) speed
32. If 4 grams of water at 1EC absorbs 33.6 joules of heat, the
temperature of the water will change by (1) 1 CE (2) 2 CE (3) 3 CE
(4) 4 CE
Physics R: Form TR8.16A
Test Review 8
TEST 8 REVIEW
Refer to the table below to answer questions 33-34
Material
Specific Heat
(J/g°C)
aluminum
0.897
copper
0.385
lead
0.129
nickel
0.444
zinc
0.388
33. A sample of each of the metals in the table above is formed into a
50-g cube. If 100 J of thermal energy are applied to each of the
samples, which metal would change temperature by the greatest
amount? (1) aluminum (2) copper (3) lead (4) nickel
34. What is the temperature change for a 50-g cube of zinc that absorbs
100 J of energy? (1) 5.15°C (2) 2EC (3) 1,940EC (4) 50EC
35. The molecules of which substance have the highest average kinetic
energy? (1) He(g) at 0EC (2) CO2(g) at 20EC (3) HCl(g) at 40EC
(4) N2(g) at 60EC
36. What happens to most materials when they become warmer?
(1) They contract. (2) They float. (3) They vaporize. (4) They
expand.
Page 5
Use the illustration below showing the parts of a refrigerator to
answer questions 43 to 45
43. The coolant becomes a
cold, low pressure gas
when it passes through the
(1) expansion valve,
(2) freezer unit,
(3) compressor,
(4) condenser coils.
44. The coolant becomes a hot,
high pressure gas when it
passes through the
(1) expansion valve, (2) freezer unit, (3) compressor, (4) condenser
coils.
45. The coolant becomes a liquid when it passes through the
(1) expansion valve, (2) freezer unit, (3) compressor, (4) condenser
coils.
46. The transfer of heat from molecule to molecule through collisions is
called (1) conduction, (2) convection, (3) radiation, (4) insulation.
37. Which occurs if two objects at different temperatures are in contact?
(1) convection (2) radiation (3) condensation (4) conduction
47. The amount of thermal energy in a material depends on what three
things? (1) Mass, density, and volume (2) Mass, temperature, and
specific heat (3) Mass, volume, and specific heat (4) Density,
volume, and temperature
38. Thermal energy moving from the Sun to Earth is an example of
which process? (1) convection (2) expansion (3) radiation
(4) conduction
48. How much energy is required to increase the temperature of 10.0
kilograms of water from 25.0°C to 61.0°C? (1) 1,500 joules
(2) 15,000 joules (3) 150,000 joules (4) 1,500,000 joules
39. Which of these is the name for thermal energy that moves from a
warmer object to a cooler one? (1) kinetic energy (2) specific heat
(3) heat (4) temperature
49. What does heat carry from objects with higher temperature to objects
with lower temperature? (1) Specific heat (2) Temperature
(3) Thermal energy (4) Mass
40. Which of the following is an example of thermal energy transfer by
conduction? (1) water moving in a pot of boiling water (2) warm air
rising from hot pavement (3) the warmth you feel sitting near a fire
(4) the warmth you feel holding a cup of hot cocoa
50. What statement is always TRUE concerning two objects in thermal
equilibrium? (1) They are at absolute zero. (2) They are at the
melting point. (3) They are at the same height. (4) They are at the
same temperature.
41. Which of the following is a statement of the law of conservation of
energy? (1) Energy never can be created or destroyed. (2) Energy
can be created, but never destroyed. (3) Energy can be destroyed,
but never created. (4) Energy can be created and destroyed when
it changes form.
51. What condition is necessary for heat to flow between two objects?
(1) They must be of the same mass. (2) They must be of the same
density. (3) They must have different temperatures. (4) They must
have different conductivities.
42. Which of the following occurs when two molecules collide? (1) The
motion is unchanged. (2) The faster molecule slows down while the
slower molecule speeds up. (3) The slower molecule slows down
while the faster molecule speeds up. (4) The direction of the
molecules changes, but their speeds remain the same.
52. Which of the following lists the phases of matter from the BEST to
the WORST thermal conductors? (1) Gas - liquid - solid (2) Liquid solid - gas (3) Solid - liquid - gas (4) Gas - solid - liquid
53. Which category of substances acts as the best thermal insulator?
(1) Metals (2) Nonmetals (3) Solids (4) Gases
Physics R: Form TR8.16A
Test Review 8
TEST 8 REVIEW
Page 6
54. Two objects are in contact. Which of the following conditions will
yield the greatest rate of heat flow between the objects? (1) Object
A is at –20°C, and object B is at 20°C. (2) Object A is at –20°C, and
object B is at 0°C. (3) Object A is at 0°C, and object B is at 0°C.
(4) Object A is at -10°C, and object B is at 10°C.
55. Which of the following is NOT a factor that determines the amount
of heat that flows through conduction? (1) The area through which
the heat flows (2) The length the heat has to travel (3) The
temperature difference (4) The color of the material
56. Nearly all of the energy reaching the Earth comes from the sun
through the process of:
(1) convection. (2) conduction.
(3) radiation. (4) cosmic ray particles.
57. A surface that is perfectly “black” has what physical property?
(1) The surface reflects all light that falls on it. (2) The surface has
the same temperature everywhere. (3) The surface emits the
smallest amount of thermal radiation. (4) The surface absorbs all
light that falls on it.
58. Black clothing becomes hot in the bright sunlight. This is best
explained by (1) radiation, (2) conduction, (3) convection,
(4) conservation of energy.
1.
2.
3.
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Answers
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