1
Q
From the proton’s perspective in Figure 124, why does the wire appear to exert a repulsive electric force rather than a magnetic force?
A
Due to length contraction of the positive charges in the wire, the proton perceives a higher density of positive charge, creating an electric field that repels it, even though in the wire’s frame this same effect is described as a magnetic force
2
Q
How does relativity explain that magnetic and electric forces are different views of the same fundamental force?
A
Depending on the observer’s frame of reference, the same phenomenon can appear as an electric field or a magnetic field; together, they form the electromagnetic force, the true unified interaction
3
Q
Why does a proton moving parallel to current in a wire experience less force than one moving perpendicular to it?
A
The relative motion changes how charges in the wire are distributed; parallel motion minimizes length contraction effects, while perpendicular motion increases field interaction
4
Q
In the proton–wire example, how can an apparently tiny relativistic contraction produce a measurable force?
A
Even a small contraction alters charge density enough to generate an electric field strength that matches the magnetic force observed in another frame of reference
5
Q
What does the proton–wire scenario reveal about the nature of magnetic forces?
A
Magnetic forces are not fundamental; they are a relativistic effect of moving charges and can be explained as electric forces seen from a different frame
6
Q
Why is the electromagnetic force described as “fundamental to the very structure of the universe”?
A
It governs both electric and magnetic interactions, underlying everything from atomic structure to light propagation, and operates consistently across frames of reference
7
Q
What gives rise to electromagnetic waves, and what range is visible to humans?
A
A changing electric field produces a changing magnetic field, creating electromagnetic waves; humans detect 400–700 nm wavelengths as visible light
8
Q
How are wavelength, frequency, and speed of light mathematically related?
A
c=λf, where c=3×108 m/sc = 3 \times 10^8 \, \text{m/s}c=3×108m/s (in a vacuum). The product of wavelength and frequency always equals the speed of light
9
Q
Why can electromagnetic waves exist even in the vacuum of space?
A
They consist of self-sustaining electric and magnetic fields that induce each other—no physical medium is required
10
Q
What determines the resonant frequency of a circuit containing a capacitor and an inductor?
A
It depends on the inductance and capacitance values; resonance occurs when incoming electromagnetic wave frequency matches the circuit’s natural frequency
11
Q
How does a radio tune to different frequencies?
A
Adjusting the capacitance or inductance changes the resonant frequency, allowing the circuit to respond selectively to specific radio signals
12
Q
What physical principle allows polarizing filters to block or transmit light?
A
Light is polarized along the electric field direction; filters absorb light oriented in certain planes, reducing intensity or completely blocking one orientation
13
Q
How do LEDs generate light differently from traditional incandescent bulbs?
A
LEDs use semiconductors where electrons jump between energy levels when powered, releasing photons without heating a filament
14
Q
What does relativity imply about time, length, and the perception of motion between different observers?
A
Observers moving relative to each other will disagree on time intervals and lengths, though all measure light’s speed as constant
15
Q
How does relativity connect electric and magnetic descriptions of the same event?
A
One observer may describe an event as caused by an electric field, while another sees it as magnetic—both interpretations reflect the single electromagnetic force
16
Q
What do we feel infrared radiation as
A
Heat
17
Q
On most infrared cameras what color represents coldness
A
Reds/oranges
18
Q
On most infrared cameras what color represents heat
A
dark Blues/purples
19
Q
Why can some radio waves still get to there destination even when a wall is in the way
A
Some objects that block waves in some wavelengths, dont in others
20
Q
What type of miniature machinery dose a microwave oven have
A
A miniature particle accelerator
21
Q
What forms of waves do Wi-fi routers use
A
Microwaves
22
Q
How dangerous is microwave radiation
A
not dangerous at all
23
Q
What dose the abbreviation UV stand for
A
Ultra violet
24
Q
When waves get a higher frequency what starts to increase
A
energy
25
Why dose UV radiation cause sun burns
UV radiation has enough energy to damage skin cells
26
Who discovered X-ray radiation and when
Wilhem Röntgen 1895
27
Why do medical X-rays only show bones, and not skin
X-rays have enough energy to go through light elements, like oxygen hydrogen etc., like those commonly found in skin, but have trouble traveling through heavier elements like calcium in your bones
28
What is ionizing radiation
radiation capable of breaking down atoms in the human body
29
What types of radiation fall under ionizing radiation
ultra violet rays, X-rays, and Gamma rays
30
Who was the first ever person to be X-rayed, and what body part was X-rayed
Wilhem Röntgen wife's hand
31
Are medical X-rays harmful, if done infrequently
No
32
Can medical X-rays harmful, if done frequently enough
Yes (It does need to be done a lot to be harmful though)
33
A wave in which the direction of vibration is perpendicular to the direction of the wave is called what?
It is called a transverse wave, which can be seen with light or radiation and looks like a guitar string moving up and down.
34
The greek letter λ is used to describe what in a transverse wave?
λ is used to describe to wavelength, which is the distance between two peaks of the wave that are next to each other
35
How would you refer to the maximum height of a wave on a wavelength?
You would refer to it as amplitude, but amplitude can also refer to the peak intensity of thinks like sound or light as well.
36
When comparing a wave with 1 Hz and one with 5 Hz, which wave would have more full wavelengths passing through a point per second?
The 5 Hz wave, as Hertz (Hz) are used to measure frequency, the measure of how many waves pass through a given point every second.
37
Using the formula for wave velocity (V=λF), what would the wavelength (λ) of a wave with 10 Hz (F) and a velocity (V) of 100 meters per second?
The wavelength would be 10 meters.
38
The speed of light is 1 million times the speed of what other speed?
The speed of light is 1 million times the speed of sound, which is why you hear thunder so much later after lightning strikes.
39
Sound waves can travel through water, solid objects, and air. Why?
Because they are longitudal and can pass through substanaces, however it requires a medium and therefor can't travel through space unlike light.
40
Can you find the wavelength (λ) of a light wave if only given a freqeuncy of 1000 Hz?
Yes, as light waves will always travel at C, the speed of light. This means a light wave with 1000 Hz has a wavelength of nearly 300,000 meters. (radio wave)
41
Wavelengths between 400-700 nanometers are what type of electromagnetic radiation?
Visible light! Anything above or below is not visible to the naked human eye.
42
The color opposite to red (700 nm λ) is called what and has a wavelength of what?
Blue, and it has a wavelength of 450-495. The color below blue is get increasingly lower wavelengths.
43
On the electromagnetic spectrum, what is the opposite of Radio Waves?
Gamma rays, which have almost 0 wavelength, up to 10 to the negative twelvth power!
44
While we don't see any wavelengths outside of the visible color range without special gear, what do they do to affect us?
They have different effects, which can be in the form of heat or deadly radiation.
45
What is caused by a proton oscillating back and forth?
The electric field around it would oscillate back and forth.
46
What did James Clerk Maxwell discover?
Light is an electromagnetic wave.
47
What is Ampere's Law?
An electric current, or any changing electric field, gives rise to a
magnetic field.
48
What is Farady's Law?
A changing magnetic field gives rise to an electric field.
49
What is Maxwell's displacement current?
The changing electric field between the plates of a discharging capacitor.
50
What was James Clark Maxwell the first to do?
Write out all these ideas in a rigorous mathematical form and explicitly define what is meant by an electric and/or magnetic “field” in the form of an equation.
51
What happens when you move a proton sitting stationary in place to a different position?
The electric field around it will change and will now be pointing away from the new position.
52
Why does Maxwell's second equation equal zero?
It is impossible to draw a closed surface through which there is a non-zero
magnetic flux.
53
How are electromagnetic waves created?
The combined effects of the oscillating electric and magnetic fields.
54
What are all colors of the rainbow?
What we perceive due to different frequencies of electromagnetic waves.
55
What happens if the electric and magnetic fields inside our eyes are oscillating at 400 trillion times per second?
Our eyes send a signal to our brain that tells us we are seeing the color red.
56
What are our eyes able to do that our bodies can not?
Detecting changing electric and magnetic fields.
57
What did Maxwell discover about light?
Maxwell discovered that light is an electromagnetic wave. He found that his math equations predicted waves moving at the same speed as light, showing that light and electromagnetic waves are actually the same thing.
58
How did Maxwell figure out the speed of electromagnetic waves?
He combined two constants from his equations and found that the result gave a speed that matched the known speed of light, about 300 million meters per second. This proved that light travels as an electromagnetic wave.
59
What are the two constants Maxwell used?
The constants are called epsilon naught and mu naught. They describe how electric and magnetic fields behave in empty space. When combined, they give a number that equals the speed of light, which helped Maxwell understand light’s true nature.
60
What was already known before Maxwell’s discovery?
The speed of light was already known from astronomers. They had measured it by watching Jupiter’s moons and noticing delays in their movement depending on where Jupiter was in its orbit.
61
Why was Maxwell’s discovery important?
It was important because it showed what light really is. Maxwell was the first person to realize that light is made up of waves of electricity and magnetism, not just something we see with our eyes.
62
How did astronomers measure the speed of light?
They measured it by watching Jupiter’s moons and seeing that the timing of their appearances changed when Jupiter was farther away. The light took longer to reach Earth, which helped them figure out how fast light travels.
63
What is a wave?
A wave is a way that energy moves from one place to another without moving the material itself. For example, when energy moves through water or air, the water or air stays mostly in the same place — only the energy moves.
64
What happens when you drop a pebble in water?
When a pebble hits the water, waves spread out and carry the energy of the splash away, but the water itself stays where it was. This shows that waves move energy, not the material they pass through.
65
How is a wave like a line of falling dominoes?
A wave is like dominoes because you can see motion move down the line, but the dominoes don’t travel anywhere. The energy moves along the line, just like a wave sends energy through a substance without moving it.
66
What are the two main types of waves?
The two main types of waves are longitudinal waves and transverse waves. They are different because of the direction the material moves compared to the direction the wave travels.
67
What is a longitudinal wave?
A longitudinal wave is when the material moves back and forth in the same direction that the wave travels. The particles vibrate along the path of the wave instead of up and down.
68
What is an example of a longitudinal wave?
Sound is an example of a longitudinal wave. When you talk, your vocal cords make the air near them vibrate back and forth, and that vibration travels through the air as sound.
69
Does sound move air from your mouth into someone’s ear?
No, sound does not move air from one person to another. It just makes the air that’s already around both people vibrate, passing the energy of the sound through the air without moving the air itself.
70
What is the main issue with incandescent lightbulbs?
They are not energy efficient as most of the energy is actually emitted in the form of infrared heat rather than visible light.
71
What is a diode?
A circuit component that allows current to flow through in one direction.
72
What is a common use for diodes?
They are commonly used to convert from AC to DC. Ex. plugginf your phone (DC battery), into the wall (AC power).
73
Define semiconductors.
A mixture of two materials that are not normally good conductors, but when combined together and exposed to external voltage, they can act as a conductor.
74
In which order were LED lights created?
Red LED lights were created first, which has the lowest energy requirement. The next LEDs were green and most recently blue.
75
Which colors can our eyes detect?
We can detect ranges of red, green, and blue. Every other color we perceive are created by our brain.
76
How does energy from sun panels turn into electrical energy?
The sun panels convert light energy into electrical energy.
77
In recent times, how has the cost of solar panels changed?
In the past, solar panels were expensive and niche. Recently, there are now many places in the world where energy costs are negative, and people are paid to generate energy.
78
What type of energy partially powers most satelites (Including the International Space Station)?
Solar energy
79
What is currently the only usable method for powering a spacecraft to go out beyond the Earth?
Chemical rockets
80
How can a light sail power spacecraft through the stars?
With a light sail, a large sheet of reflective material is unfolded, which catches sunlight. This light pushes the spacecraft to accelerate it at a very small amount.
81
Hypothetically, how fast can a spacecraft using the lightsail go?
The only limit would be the speed of light itself.
82
The audio component of television is typically transmitted via _____?
FM
83
The video component of television is typically transmitted via ______?
AM
84
To produce an image, the earliest televisions used what?
a cathode ray tube (CRT)
85
What is a "cathode"?
a collection of negative charge
86
What is an "anode"?
a collection of positive charge
87
What is a cathode ray tube?
a device that accelerates electrons and then magnetically deflects them onto parts of a screen to create an image
88
What does the "cathode" do in a cathode ray tube (CRT)?
emits the electrons
89
After being emitted by the cathode in a CRT, what happens to the electrons?
they are accelerated by high voltages toward an "anode"
90
How is a small burst of light created in a cathode ray tube (CRT) after the electrons have been emitted by the cathode and sped up by high voltages towards the anode?
they will then pass through a magnetic field and are defelcted onto a phosphorescent screen, where energy from the collisions will create small bursts of light
91
What screen do electrons in a cathode ray tube (CRT) deflect onto?
a phosphorescent screen
92
True or False? An image on the television screen is created all at once
93
Describe where the image on a television screen is created with respects to the screen
from the top left corner to the bottom right corner, row by row, so fast that it cannot be seen by the human eye
94
True or False? Most TVs today still use cathode ray tube (CRT) displays
False; they instead use liquid crystal displays (LCDs)
95
What do liqid crystal displays (LCDs), which are used in most TVs today, take advantage of?
the polarization of light
96
What is another name for a "picture element"?
pixel
97
Cyan results from the absence of what color?
red
98
Magenta results from the absence of what color?
green
99
Yellow results from the absence of what color?
blue
100
What three colors make white? (refferring to light)
red, green, and blue
101
Red and green make? (referring to light)
yellow
102
Green and blue make? (referring to light)
cyan
103
Red and blue make? (referring to light)
magenta
104
What are the primary colors of ink also known as?
the subtractive primaries
105
What are the primary colors of ink (aka subtractice primaries)? (Hint: there are three)
cyan, magenta, yellow
106
How does ink gets it color?
by absorbing light rather than emitting light
107
The cells in our eyes, known as cones, are sensititve to what three colors (known as the three primary colors of light)?
red, green, and blue
108
Why do electronic devices only need to admit the three primary colors of light (red, green, & blue)?
because all the other colors we perceive are combinations of those three primary colors of light
109
Why do we not notice relativity's effects in our everyday lives?
they are so small for everyday speeds, you would never notice them
110
At what speed would be able to notice the effects of relativity (a difference in time and length between moving objects)?
the speed of light
111
The effects of relativity can be summed up by what?
the Lorentz factor
112
What is the equation for the Lorentz factor?
y = 1 all over (the square root of(1-v^2/c^2))
113
What does the Lorentz factor tell us?
the difference between how much time you experience versus how much time another observer is going at speed v relative to you
114
What can be assumed from the Lorentz factor if any speed v is much less than c?
the factor will basically just equal 1
115
In the Lorentz factor equation, if speed v is approaching c, then the factor is assumed to be getting larger or smaller?
larger
116
All the strange things about the theory of relativity are a consequence of what observation? (Remember the Lorentz factor)
that c is the same for all observers
117
Why can nothing ever exceed the speed of light?
because c is the same for all observers/no matter how fast you go, light is always going much faster, so you’ll never be able to catch it
118
In the Lorentz factor equation, what variable is often referred to as the speed of light?
the constant c
119
Although the constant c is referred to as the speed of light, it is more precisely?
the speed of light in empty space
120
How does passing through a substance, such as glass, affect the speed of light?
it slows it down (but still doesn’t change any analysis through the Lorentz equation)
121
Why is the constant c from the Lorentz factor equation often referred to as the speed of light?
because it was the first thing reocngized to travel at the speed
122
True or False? The constant c is specifically tied to the motion of light since it is often referred to as the speed of light
123
What key assumption did Einstein make about the speed of light?
The speed of light (c) is constant for all observers, regardless of their motion.
124
What did Einstein reject that earlier scientists believed in?
The idea of a mysterious “ether” through which light was thought to travel.
125
What question did Einstein ask about chasing a beam of light?
If you moved at light speed, would the light appear to stop moving?
126
What was Einstein’s answer to that question?
No one can reach or match the speed of light. Every observer measures light as moving at speed c.
127
If two observers both measure the speed of light as c, what must differ between them?
Their measurements of time and distance.
128
What is the thought experiment with the scooter meant to show?
That two observers (you and the scooter rider) both measure light’s speed as c, even though they disagree on distance and time.
129
What paradox arises in the scooter experiment?
Both observers see light move at c, but they disagree on how far it travels in one second.
130
How did Einstein resolve this paradox?
By proposing that time itself is relative—it passes differently for moving observers.
131
What is the term for time slowing down for a moving observer?
Time dilation.
132
Does each observer see their own time as normal?
Yes — each observer experiences their own clock ticking normally.
133
How does each observer view the other’s clock?
Each sees the other’s clock as running slower than their own.
134
What is length contraction?
The shortening of measured distances for objects moving close to the speed of light.
135
In the spaceship example, why do travelers experience a shorter trip time than observers on Earth?
Because their time runs slower due to time dilation.
136
From the spaceship crew’s perspective, how far is the 25 light-year journey?
Only about 3.5 light-years, due to length contraction.
137
What overall conclusion does Einstein’s theory lead to about space and time?
Space and time are relative—different observers measure different lengths and times depending on their motion.
AcaDec_1920s
flashcards
Decks in class (24)
# Cards
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Social Science - Section 1130
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Social Science - Section 2145
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Social Science - Section 3111
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Social Science - Section 479
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Literature Section 281
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Literature Section 3204
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Literature Section 4195
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Art Section 1 - part 1205
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Art Section 1 - part 2191
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Art Section 2135
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Art Section 3113
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Art Section 491
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Art Section 571
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Science Section 1188
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Science Section 2141
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Science Section 3123
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Science Section 4137
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Economics - Macro212
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Economics - Micro222
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Music Section 1346
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Music Section 2189
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Music Section 3146
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Music Section 4121
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Economics - Section 4112
