What is the wavelength of 345 Hz sound in air if the speed of sound is 345 m/s? 0.1 meters 0.345 meters 1.0 meter 3.45 m

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What is the wavelength of 345 Hz sound in air if the speed of sound is 345 m/s? 0.1 meters 0.345 meters 1.0 meter 3.45 m - PowerPoint PPT Presentation

What is the wavelength of 345 Hz sound in air if the speed of sound is 345 m/s? 0.1 meters 0.345 meters 1.0 meter 3.45 meters sound is not characterized by wavelength. C. Why is it difficult to localize sound under water? sound doesn’t travel under water

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What is the wavelength of 345 Hz sound in air if the speed of sound is 345 m/s?
• 0.1 meters
• 0.345 meters
• 1.0 meter
• 3.45 meters
• sound is not characterized by wavelength

C

Why is it difficult to localize sound under water?
• sound doesn’t travel under water
• sound is heavily attenuated (suppressed) underwater
• our ears can’t hear sound underwater
• sound speed is fast in water, throwing off our “calculation”
• sound doesn’t have a localized source under water

D

Mid-range sound is about 1 kHz. What is the wavelength of mid-range sound? (c = 345 m/s)
• 0.1 m
• 0.345 m
• 1.0 m
• 3.45 m

B

• There are no physical restrictions on its size
• Less than 0.345 m across
• Greater than 0.345 m across
• Depends how much you pay: \$\$\$bigger
• It’s mostly a matter of aesthetics/design

B

How do you differentiate a piano from a violin if both are playing the same note?
• The main wavelength of the two is different
• The main frequency of the two is different
• The amplitude of the sound wave is different
• The two look different on an oscilloscope
• The high-frequency content is different for the two

E, but D true

When you wipe a CD, you may scratch it. Would you rather risk a radial scratch or a tangential scratch?
• Neither one is likely to have an effect
• Both will have the same effect
• The radial scratch is worse: affects many spirals
• The tangential scratch is worse: many bits in a row disrupted
• CDs cannot be scratched

E

NAND

A B C

0 0 1

0 1 1

1 0 1

1 1 0

• What logic table would you get out of a NAND gate with the inputs tied together?

A

C

A

B

C

D

A C

0 0

1 0

A C

0 0

1 1

A C

0 1

1 0

A C

0 1

1 1

C

AND

OR

A B C

0 0 0

0 1 0

1 0 0

1 1 1

A B C

0 0 0

0 1 1

1 0 1

1 1 1

• What is (1 AND 1) OR (0 AND 1)?
• 0
• 1
• indeterminate

1

1

?

0

1

B

NAND

AND

OR

A B C

0 0 0

0 1 0

1 0 0

1 1 1

A B C

0 0 1

0 1 1

1 0 1

1 1 0

A B C

0 0 0

0 1 1

1 0 1

1 1 1

• Which of the following functions does this contraption look like (using only NAND gates)?
• NAND
• AND
• OR
• NOR
• XOR

A

C

B

C

How do TV remotes communicate with the TV?
• ultrasonic acoustic (sound) pulses
• bursts of infrared light
• via electrons/current flow
• by manipulating the electric field in the room

C

Why do you think the remotes avoid long sequences of ones or zeros (staccato nature)?
• this is the most efficient way to encode data
• this avoids confusion over blockages (shadows)
• this avoids confusion over natural sources (glints)
• all binary information is intrinsically this way
• it’s an arbitrary choice with no real meaning

C or B

What do you think would happen if two remotes tried to access the same receiver at the same time? Keep in mind that to the receiver, it’s all binary: it either sees a light or it doesn’t.
• The signals would jumble together and confuse the receiver
• The receiver would be able to sort out who is who
• The receiver would store the second signal and process it later
• The receiver would block out the second one, listening only to the first

A

If each remote takes 100 ms to complete its transmission, roughly how many seconds would it take for 25 students to click in if you require less than 10% overlap rate?
• 2.5 seconds
• 25 seconds
• 50 seconds

B

TV remote controls use infrared light (LEDs). There is plenty of infrared light in sunlight. Why doesn’t your TV do weird things when the sun hits it?
• because the sun isn’t bright enough in infrared to do this
• because sunlight is constant—not flashing like the remote
• because the sun’s spectrum is broader than the IR LED
• because even if flashing due to waving trees, it won’t reproduce an understandable code

B and D

How does energy get from the sun to us on earth?
• the solar wind carries heat
• the vacuum of space conducts heat
• electromagnetic radiation (light, IR, etc.) carries it
• We place an order, and one month later, it’s delivered

C

• 1 mm
• 1 m
• 100 m
• 1 km
• 100 km

B

• 0.25 meters
• 0.75 meters
• 3 meters
• 5 meters
• length is irrelevant

B

Why can’t you fit more stations into the FM radio band?
• It’s strictly regulatory: you could fit many more
• It’s a matter of bandwidth: less space means poorer sound quality
• It would be impossible to build radios to separate out stations any closer together than 200 kHz
• Nobody would want any more stations: most are bad anyway

B

If I place a sphere in an electric field that points to the right, how will charges distribute themselves on the sphere?
• electrons go right, leaving positive on left
• electrons go left, leaving positive on right
• electrons go up, leaving positive on bottom
• electrons go down, leaving positive on top

B

Why does the mesh cage block radio waves but not light, if both are electromagnetic radiation?
• light and radio are not that similar
• photons of light are small enough to make it through
• the mesh only blocks polarized sources of radiation
• the electric field for light oscillates too quickly for electrons to redistribute around holes
• light can’t be thought of as oscillating electric fields

D

Is the frequency of 1 GHz (109 Hz) considered to be a microwave frequency?
• No: nowhere close
• Yes: it’s in the right range
• Yes, but just barely
• No, but just barely not

B

If I put a positively charged rod near a stream of water, do the oxygens or hydrogens tend to orient toward the rod?
• the oxygens do, since they’re more negative
• the hydrogens do since they’re more positive
• neither: water molecules don’t care
• both happen equally

A

If a positively charged rod attracts the stream of water, what will a negative rod do?
• repel the stream
• still attract the stream
• it will have no effect

B

How long would it take a 1000 W microwave to heat a 0.1 kg hot dog by 80 C if it’s heat capacity is 2000 J/kg/C?
• 5 seconds
• 8 seconds
• 16 seconds
• 60 seconds

C

• photons
• protons
• electrons
• Charles
• gamma rays

C

Why are the primary colors red, green, and blue, and not magenta, yellow, and cyan?
• Because we’re mixing light, not pigments
• Because this mixing is additive, not subtractive
• Because our eyes have cones responding to the colors red, green, and blue
• Because white light includes red, green, and blue
• Dr. Murphy will tell us in a future lecture

A, B

What is the charge on the CRT anode?
• Positive
• neutral
• negative
• \$3.95

A

HDTV has about 700 lines/frame. The frame rate remains about 30 fps. What is the horizontal scan frequency?
• 30 Hz
• 700 Hz
• 15,750 Hz
• 21,000 Hz
• zero Hz

D

One form of HDTV is 30 fps, non-interlaced. What is the vertical scan frequency?
• 30 Hz
• 700 Hz
• 15,750 Hz
• 21,000 Hz
• zero Hz

A

How low must a mirror go if you want to see your feet?
• all the way to the floor
• to half the distance from feet to eyes

C; B is close

What do you see from underwater looking up at the sky?
• You don’t see out: only a reflection of the floor
• You see part of the sky, but not all the way to the horizon
• You see all of the sky, filling the entire vertical view
• You see all of the sky, but confined to a smaller circle
• You see the sky in a circle, and outside of this see a reflection of the floor

D and E

Do the sides of aquariums that look like mirrors to you also look like mirrors to the fish inside?
• Yes: every bit as much
• Yes, but not straight ahead: only to the sides
• No: nowhere does it look like a mirror
• They see a partial reflection, like a half-mirror

B

If you want to spear a fish underwater, how should you aim?
• Aim higher than where you see the fish
• Aim right at where you see the fish
• Aim lower than where you see the fish
• It doesn’t matter: you’re gonna miss anyway

C

• Aim above where you see the fish
• Aim right at where you see the fish
• Aim below where you see the fish
• Doesn’t matter: laser guns don’t exist

B

Why is corneal surgery (and contact lenses) so effective without messing with the eye’s lens?
• Because the lens adjusts to the cornea
• Because most of the refraction happens at the air/cornea interface
• Because the eye otherwise would be distorted by the surgery
• Because the cornea heals fastest

B

What would fish goggles be like:
• Just like ours: holding a pocket of air
• Much like ours, but holding a pocket of water
• Fish can see fine out of water
• They would be bulbous and full of air
• They would be bulbous and full of water

B

• each additional paint absorbs yet more light
• brown is a natural color that tends to emerge
• the chemicals mix and change to make brown
• for the same reason that dirt is brown
• this only happens with cheap paints

A

How might blue sky and orange sunsets be related?
• There’s no good reason why they would be
• Air pollution is responsible for both
• The air is subtracting orange light from the sun
• The air is subtracting blue light from the sun
• It’s just the way things are…

D

What color(s) will a red shirt absorb?
• red
• green
• blue
• green and blue
• red and blue

D

Why isn’t pink in the spectrum?
• pink is not an actual color
• pink requires red plus some white
• pink is mostly red, with some green and blue mixed in
• pink has a wavelength, it’s just beyond the “visible” range

B or C

Magenta paint absorbs green well. If you wanted to make magenta via additive sources, what light(s) would you use?
• red
• green
• blue
• red and green
• red and blue

E

Some parking garages use low pressure sodium vapor lamps (very orange), casting a single wavelength (589 nm). What does a blue shirt look like in this light?
• still blue
• a blueish-orange
• magenta
• black
• nothing has color in this light

D

Why is the lather from blue soap still white?
• a chemical reaction changes the nature of the soap
• the water dilutes the blue
• the lather has many reflective surfaces
• the walls of the bubbles are so thin they’re clear
• never happened

C and D

Using [(n1– n2)/(n1 + n2)]2, what is the reflection fraction of glass vs. air at n=1.5?
• 0.02
• 0.04
• 0.08
• 0.20
• huh?

B

• north
• south
• east
• west
• could be anywhere

C

• We’re mostly indoors then, and simply don’t notice
• The rain/sun conditions are rarely met during mid-day
• They happen all the time, if we were only more observant
• The sun is too high in the sky; rainbow is toward ground
• It’s too bright to notice them during mid-day

D

GoldenEye: What’s wrong with this picture
• any plane a runner can catch up to isn’t serious about taking off
• Bond got a late start going off the cliff
• The plane (with engine on) will go faster than Bond will fall
• Bond wasn’t in a full-dive to minimize area
• The building blew up at the end (of course)

all

Speed: What’s wrong with this picture?
• The gap is level
• The gap is too long: several bus-lengths
• The bus lurches upward on “take-off”
• The bus falls down onto the other side (originally at the same level)
• There is no spoon!

all

Two Towers: What’s wrong with this picture?
• Gandalf gets a late start
• Gandalf catches up to his sword
• Gandalf falls faster than the balrog at first, but later same speed
• All those swats, and still falling straight without hitting wall!
• Stupid balrog has wings: what—he forgot?!

all

If you want to make a 3D movie in full color, what sort of glasses do you need to use?
• blue for left, red for right
• red for left, blue for right
• blue/red in either order
• polarized: vertical vs. horizontal
• polarized: 45 left-ward vs. 45 rightward

E or D

Ozone takes out 90% of UVB when sun is straight overhead. What effective SPF does ozone have if the sun is at 30 vs. straight up, and thus travels through twice as much ozone?
• SPF 2
• SPF 5
• SPF 10
• SPF 20

C

What’s a fool-proof way to know whether a light is based on exciting atomic transitions (like neon, fluorescent) or on thermal incandescence (hot filament)?
• if it’s colored, it’s not incandescent
• if it looks white, it’s incandescent
• the shape of the light tells you
• look at it with a spectrograph: lines means atomic

D is best

Which would produce greater tides: our own moon or a moon twice as massive twice as far from earth?
• Our own moon produces larger tides
• They would both produce the same tidal effect
• The alternate moon would produce a bigger tide
• There is no moon

A