Exam 3 Flashcards
(181 cards)
1
Q
Capillary waves
A
The smallest waves
2
Q
Dispersion
A
where the velocity depends on wavelength
3
Q
Gravity Waves
A
Larger waves
4
Q
Wavelength of capillary waves
A
Less than about 2 cm
5
Q
Example of dispersion
A
The longer the wavelength, the slower the wave speed
6
Q
What provides the restoring force in the oscillation of small water waves?
A
Surface tension of the fluid
7
Q
What does tension act like in water waves?
A
A string or drumhead
8
Q
Deep vs Shallow water speed
A
Deep: faster
Shallow: slower
9
Q
Wave height
A
Is measured from the trough to the crest
10
Q
Wave steepness
A
Is measured by dividing the height by the wavelength
11
Q
Fetch
A
The distance over which a constant wind blows to generate a wave field
12
Q
Fully developed sea
A
A sea for which the input of energy to the waves from the local wind is in balance with the transfer energy among different wave components, and with the dissipation of energy by wave breaking
13
Q
Whitecaps
A
Are surf that breaks in deep water when the height ~ wavelength divided by 12
14
Q
Why do ocean waves “break” as they approach a gradually sloping beach?
A
Because they slow down, so their wavelengths decrease and heights increase
15
Q
Neap tides
A
Are tides that have less range from low to high. The moon is vertical from the Earth
16
Q
Spring tides
A
Are tides that have more ranges from low to high. The moon is horizontal from the Earth
17
Q
What causes ocean tides?
A
The gravitational pull of the moon on water
18
Q
When does high tide occur?
A
Every 12 hours and 15 minutes (an hour late each day)
19
Q
Seiche wave
A
A standing wave in an enclosed of partially enclosed body of water (sway back and forth)
20
Q
Tsunami waves
A
A series of water waves caused by the displacement of a large volume of a body of water
21
Q
Hull wave
A
The wave that forms at the hull of a ship when it moves through the water
22
Q
Bow wave
A
The wave that forms at the bow of a ship when it moves through the water
23
Q
Quarter wave
A
The wave that forms at the quarter of a ship when it moves through the water
24
Q
Planing hull
A
Are designed to rise up and glide on top of water when enough power is supplied to avoid high wave drag and can travel much faster
25
Wake
The wave pattern on the water surface downstream of an object in a flow, or produced by a moving object caused by density differences of the fluids above and below the free surface and gravity
26
Why is the maximum speed of a displacement ship related to its water length?
Hull wave speed
27
What provides the restoring force in the oscillation of large water waves?
Gravity
28
How far and fast do tsunami waves travel?
Transoceanic distances at 200 mph (w/ limited energy loss)
29
Hull speed
The speed of a gravity wave in knots is equal to 1.34 times the square root of the wavelength in feet
30
Components of a ship's wave pattern
Bow wave, stern wave, transverse wave, turbulent wake, and turbulence region adjacent to the ship's hull
31
At which end of the electromagnetic spectrum are radio waves found? (wavelength/ frequency)
1 mm and 100 km/ 3 THz and 3 kHz, 300 MHz and 300 GHz
32
At which end are
| gamma rays found? (wavelength/ frequency)
1 pm, 10^-11 m/ 300 EHZ, >10^19 Hz
33
At which end of the visible spectrum of light is “blue” found? (wavelength/ frequency)
495 nm
34
By using the concept of “electric field,” explain how the attractive or repulsive force arises
between charges at rest.
+ & - attract
| +& +, - & - repel
35
What happens in an electromagnetic wave to make it more than a simple combination of
electric and magnetic fields?
The E and B fields are perpendicular from each other and is a transverse wave
36
Electric charge
property of the tiniest particles
| composing all matter: electrons, protons, and many other unstable or elusive particles.
37
Electrostatic force/ Coulomb force
The force between charges at rest
38
Electric field (E field)
refers to the condition created in the
| space surrounding a charged body by its charge.
39
Electric current (electricity)
When electrons move in metals
40
Magnetic fields (B field)
A field that is proportional to their velocity and to their electric charge
41
Electromagnetic induction
And when magnetic fields themselves change,
| electric fields are also generated
42
Electromagnetic radiation
When a net charge or current varies sinusoidally, corresponding sinusoidal electric and magnetic fields
are generated which,
sustain and regenerate one another.
43
Electromagnetic spectrum
The electromagnetic spectrum is the collective term for all possible frequencies of electromagnetic radiation
44
What happens when a particle has zero charge?
Neither attract not repel
45
Coulomb's Force Law
expressing the force of one
| charge on another
46
F12=(k)(q1q2/r^2)
Force (F) depends on the product of q1 and q2 and inversely on the square of the distance
r between the charges. k is the constant,
a universal constant of proportionality. (not a spring constant!)
47
What are the 2 parts of Coulombs force?
. A charge creates an electric field around it
| .Another charge placed in a region of electric field experiences a force that is proportional to that field, F12=q2E1
48
Charge of one electron
1.6021766208(98)*10^−19 coulombs
49
Mass of one electron
9.10938356(11)*10^−31 kg
50
Size of one electron
Unknown
51
What is a kilohertz (kHz)?
A measure of frequency equivalent to 1,000 cycles per second.
52
What is a megahertz (MHz)?
One million hertz, especially as a measure of the frequency of radio transmissions or the clock speed of a computer
53
Describe the differences between radio waves and microwaves
```
Microwaves- used for point-to-point communication and for many technical purposes, sub-class of radio waves
Radio waves- used for long distance communications
```
54
Why are transmitting antennas for low-frequency radio waves normally very large, but
microwave antennas are usually small.
Because it's stronger the taller the antenna is
55
What does “amplitude modulation” mean? (AM)
Waves at fixed carrier frequency vary in amplitude
56
How does a prism produce colored light from colorless (white) light?
White light is a uniform mixture of all colors
57
Hertz
The SI unit of frequency, equal to one cycle per second
58
Gigahertz
A unit of frequency equal to one billion hertz, or cycles, per second
59
Frequency modulation (FM)
Waves sweep up and down in frequency at varying rates
60
Carrier frequency
Separates stations from one another and can be rejected
61
Sidebands (sb)
(left-sb and right-sb) Has the information that needs to be transferred
62
Bandwidth
The width and/ or range of frequencies in a band in a modulation that is used for transmitting signals and is the spreading of a carrier into sidebands.
63
Microwaves
EM radiation at frequencies typically between 300 MHz (0.3 GHz) and 300 GHz
64
Visible light
EM that our eyes can see from 400-680 nm
65
Infrared light
Hot light that cannot be seen (681-782nm)
66
Ultraviolet light
Waves like the sun waves that cannot be seen (401-470nm)
67
Blackbody radiation
emitted from all matter
| at any temperature like a lightbulb
68
Incandescent
emitting light as a result of being heated
69
Spectral distribution
Broad mixtures of different frequencies in the visible spectrum
70
Why does the clear daytime sky have a bluish color?
Because the unpolarized light becomes polarized when it scatters. (Will always show strong polarization)
71
Name some circumstances where naturally occurring light
| polarization may be observed.
The sun and double rainbow
72
Explain the difference between reflection and refraction.
Reflection- reflects off a flat mirror
| Refraction- bent toward the normal when entering the slower medium and away when entering the faster medium
73
Why can you sometimes see not only one but two concentric rainbows? In what direction
relative to the sun do rainbows appear?
Because the light scattered in the rainbow is strongly polarized and thanks to Alexander's dark band . Away from the sun
74
Where should you look to see a “sun dog”?
Away and next to the sun
75
Rayleigh scattering
Occurs when the scatters are much smaller than the wavelength of light
76
Polarization
If the amounts of horizontal and vertical polarization become unbalance
77
Incident rays
The ray of light approaching the mirror
78
Reflected rays
The ray of light that leaves the mirror
79
Normal direction
Divides the angle between the incident and reflected ray into two equal angles.
80
Index of refraction
A number greater than 1, indicating that light travels more slowly than in vacuum
81
Unpolarized vs polarized
Unpolarized- E horizontal
| polarized- E vertical
82
Angle of incidence
0 (perpendicular)-90 (grazing on surface) degrees
83
Refraction ray
Bending away from the normal
84
Reflection ray
A ray of light that leaves the mirror
85
Prism
A solid geometric figure whose two end faces are similar, equal, and parallel rectilinear figures, and whose sides are parallelograms
86
Primary rainbow
42 degrees from anti-solar point
87
Secondary rainbow
51 degrees from anti-solar point
88
Sun dog
Consist of a pair of bright spots on either horizontal side on the sun
89
How is the spacing of energy levels related to the frequency (or wavelength) of emitted or
absorbed light?
Emitted- from high to low energy state
| Absorbed- when the amount of energy provided matches the difference in energy of 2 energy levels
90
What is a photon? (particles of light)
Light emitted and absorbed by matter in individual bursts
91
How can the presence of different chemical elements be determined remotely using light?
By comparting the patterns of spectral line
92
Why do stars have different colors?
Because of the temperature of the star (works like a lightbulb)
93
White light
A mixture of all visible wavelengths or frequencies
94
Energy of a photon
Delta E= h * f
95
Spectral lines
A dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies
96
Spectroscopy
A method to determine the composition of substances and conditions of temp, pressure, ionization, and chemical environment
97
Spectroscope
An apparatus for producing and recording spectra for examination
98
Fraunhofer absorption line
A line caused by sodium vapor in the sun's cool outer layers (2 closed spaced wavelengths)
99
Emission lines
An isolated bright or dark line in a spectrum produced by emission or absorption of light of a single wavelength
100
Additive primaries of color (ideal primaries)
RGB (mixing of light)
101
Subtractive primaries of color
Cyan, magenta, yellow (mixing of paint, ink, or dyes)
102
Color triangle
An arrangement of colors within a triangle, based on the additive combination of three primary colors at its corners
103
Chromaticity coordinates
R= (R)/(R+G+B), same for the other colors, B=1-R-G
104
Chromaticity diagram
An objective specification of the quality of a color regardless of its luminance
105
Color gamut
various levels of colors that can potentially be displayed by a device
106
Tristimulus values
The three values representing the amounts of red, green, and blue light that in combination match a specific color
107
Digital color
0-225
108
Blind spot of the eye
The specific scotoma in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc
109
Rods
Numerous and sensitive but not to color
110
Cones
Sensitive to color and more concentrated
111
Anomalous color vision
The absence of malfunction of one or more of the chromatic sensitivities
112
Protanomaly
Red shift: red-green confusion (8% Caucasian males)
113
Deueranomaly
Green shift: red green confusion
114
Tritanomaly
Weak blue: blue-yellow confusion
115
Metamerism
2 objects appearing to be the same color under one illumination but different under another
116
After image
A non-specific term that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased
117
Chromatic adaptation
The human visual system’s ability to adjust to changes in illumination in order to preserve the appearance of object colors
118
Where is “white” located in a color triangle or chromaticity diagram? Why?
In the middle of the triangle because that's where all of the colors mix
119
Why is it impossible for any color photograph, computer display, projected image or painting
to perfectly recreate the colors of a rainbow?
Because the color gamut of each machine is different. A rainbow consist of additive primaries of color and a device consist of secondary primaries of color
120
How does the human eye (and brain) sense color?
When an object is observed, it is first focused through the cornea and lens onto the retina, a multilayered membrane that contains millions of light-sensitive cells that detect the image and translate it into a series of electrical signals. In the brain, the optic nerves from both eyes join at the optic chiasma where information from their retinas is correlated. The visual information is then processed through several steps, eventually arriving at the visual cortex, which is located on the lower rear section of each half of the cerebrum.
121
Optical image
An image formed by the refraction or reflection of light
122
Focal length
The distance from the lens to the focal point
123
Focal point/ common point
Where if rays that meet the lens at all points across its face
are refracted so they intersect
124
Concave/ diverging lenses
Lens that spread out the parallel rays and are thinner at the center than the edges
125
Convex/ converging lenses
Lens that bring parallel rays together and are thicker at the center than the edges
126
Focus
Sharp image
127
Depth of focus
Depends on parallelism of converging rays: more parallel= less critical the focusing
128
Magnification
Depends on ratio of image and object distances
129
Pinhole
A very small hole
130
Aperture
a hole or an opening through which light travels.
| light-gathering vs depth of focus
131
Digital photography
An electronic sensor records the pattern of light in the image
132
Telephoto lens
long focal length
133
Zoom lens
Variable focal length, close up-telephoto
134
Macro lens
Extreme close up, high magnification
135
Wide-angle lens
Wide field of view, low magnification
136
Sensitivity
Speed of recording medium
137
Exposure time
Blur of moving object
138
What causes very dim images through a pinhole?
Little or no light
139
What causes brighter but fuzzy images through a pinhole?
Bigger pinhole
140
Bigger lens=
More light
141
Smaller lens=
Greater depth of focus
142
Pixel
A minute area of illumination on a display screen, one of many from which an image is composed.
143
Pixilation
Is caused by displaying a bitmap or a section of a bitmap at such a large size that individual pixels, small single-colored square display elements that comprise the bitmap, are visible
144
Sun glitter
A bright, sparkling light formed when sunlight reflects from water waves
145
Horizon
The line at which the earth's surface and the sky appear to meet
146
Hull-down
The upper part of a vessel or vehicle is visible, but the main, lower body (hull) is not
147
Mirage
Light rays bend (refract) in layers of air at different temperature
148
Inferior mirage
Seen below real object
149
Exterior mirage
Seen above real image
150
LASER
Light Amplification by Stimulated Emission of Radiation
151
3 basic process of light interaction with matter
1. Absorption
2. Spontaneous emission
3. Stimulated emission
152
Absorption
Light is absorbed and atoms move up one energy level
153
Spontaneous emission
Energy is released (light) and atoms move down simultaneously
154
Stimulated emission
Atoms in upper state are stimulated to move down and produces 2 photons.
Stimulated by light going in
155
Incoherent light
Each photon has its own direction,
| polarization and wavelength. (sunlight, ordinary lamps)
156
Coherent light
Photons are identical, indistinguishable,
| and form a single EM wave. (lasers)
157
Which came first MASER or LASER?
MASER
158
4-level laser scheme
1. Ground state
2. Excited state
3. Upper laser level
4. Lower laser level
159
What happens at the ground level?
All atoms are relax & stay until disturbed
160
What happens at the excited level?
Spontaneous emission
161
What happens at the upper laser level?
Atoms decay spontaneously, have a longer lifetime, atoms accumulate, and fill up layer
162
What happens at the lower laser level?
Atoms drains spontaneously quick and have a short lifetime
163
Laser gain medium
A collection of atoms, molecules
or other system of quantum energy levels having a
population inversion
164
Laser cavity
(With end mirrors) allows light to bounce back
| and forth through the gain medium
165
Population inversion
Occurs while a system (such as a group of atoms or molecules) exists in a state in which more members of the system are in higher, excited states than in lower, unexcited energy states
166
What is needed to create and maintain the population inversion?
A pumping mechanism (incoherent)
167
Explain why the horizon stands out sharply on a clear but windy day at sea
Light is from the lower part of the sky so they look lighter
168
Explain why the horizon stands out invisible on a clear windless day at sea
The light is from the upper part of the sky so they look darker
169
When you look from the side of a boat into still water, why can you see fish clearly when they
swim near the surface close to the boat but only with difficulty if they swim further away (even
though at the same shallow depth)?
Clearly: because the waves are tilted towards you
Difficulty: because the waves are titled away from you
170
Why does the setting sun sometimes appear flattened as it reaches the horizon?
Because the tilted waves are tilted at right angles
171
Why can mirages be seen not only in the desert but on roads even at
freezing temperatures?
Because the road is reflecting the sky and the layers have different temperatures
172
What are some application for lasers?
1. Medical: surgery, dermatology, ophthalmology, dentistry
2. Industrial: machining, mining, propulsion, lithography
3. Environmental, ranging, military, communications
4. Consumer: CD, DVD, grocery scanners, printers
5. Scientific: spectroscopy, quantum computing
173
What does LED stand for?
Light Emitting Diode
174
How do LEDs work?
Electrons pass through a junction between two
types of semiconductor material. When they
encounter a suitable but unfilled quantum energy
level they can “fall in” to it and give off the energy
difference as a photon of light.
175
How do you determine the wavelength of LEDs?
wavelength= (hc)/(delta E)
176
What are some semiconductors for LEDs?
```
Gallium arsenide (IR)
Gallium phosphide (R, yellow, orange, green)
Gallium nitride, indium gallium nitride (blue)
```
177
Lumen
SI unit of luminous flux, a measure of the power of light perceived by the human
eye
178
What's the maximum possible luminous efficiency?
683 lm/w (achieved by green light at 555nm)
179
Advantages of LED
1. High efficiency
2. Varied color
3. Small
4. Fast on/off time
5. Easy dimming
6. Little IR/ heat
7. No burn-out, gradual failure
8. Long lasting
9. Sturdy, shock resistance
10. No mercury or hazardous chemical
180
Disadvantages of LED
1. Expensive
2. Temperature dependence (in/outdoor)
3. Voltage sensitivity
4. Light quality
5. Blue pollution
181
Light pollution
Excessive, misdirected, or obtrusive artificial light
