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Astrophysics > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

What is period?

A

The time required for the wave crest at point A to reach point B. Units is seconds.

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2
Q

What is amplitude?

A

Distance from the midpoint to the crest or to the trough. Basically the height.

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3
Q

What is wavelength?

A

Distance from the top of one crest to the top of the next crest, or distance between successive identical parts of the wave

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4
Q

What is frequency?

A

The number of wave crests passing point A each second. Units is Hz.

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5
Q

What is an echo?

A

A reflected sound wave.

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6
Q

Difference between pitch and frequency

A

Pitch is the human perception of frequency. High pitch, high frequency, low pitch, low frequency.

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7
Q

What is doppler effect?

A

A change in pitch/frequency due to the source of sound is moving or you are moving from the source of sound.

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8
Q

Sound travels in…

A

In a medium. A gas, solids, or liquids, but not in a vacuum. That’s why sound waves are mechanical waves.

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9
Q

Blue shift vs red shift

A

Blue shift: increase in frequency due to doppler effect
Red shift: decrease in frequency due to doppler effect

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10
Q

Astronomers find that light emitted by a particular element at one edge of the Sun has a slightly higher frequency than light from that element at the opposite edge. What do these measurements tell us about the Sun’s motion?

A

It tells us how fast the sun is spinning around its axis.

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11
Q

Why can the tremor of the ground from a distant explosion be felt before the sound of the explosion can be heard?

A

Sounds travels faster by ground than through air so we feel it in the ground first.

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12
Q

A shock wave occurs when…

A

The speed of the wave is faster than the speed of sound.

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13
Q

The phenomenon of beats…

A

Absolute value of the two beats given.

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14
Q

Rank the beat frequency
A. 132 Hz, 136 Hz
B. 264 Hz, 258 Hz
C. 528 Hz, 531 Hz
D. 1056 Hz, 1058 Hz

A

B,A,C,D

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15
Q

Why will a struck tuning fork sound louder when it is held against a table?

A

The larger surface is vibrating and pushing more air molecules making the sound louder.

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16
Q

Suppose a sound wave and an electromagnetic wave have the same frequency. Which has the longer wavelength? Why?

A

The electromagnetic because it is moving much faster than the sound wave. speed = wavelength x frequency

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17
Q

What kinds of waves can show interference?

A

Any wave can show interference.

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18
Q
  1. Sound can NOT be
    a) reflected.
    b) absorbed.
    c) diminished/ Increased by interference.
    d) none of these.
A

D

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19
Q

How did wind-generated resonance affect the Tacoma Narrows Bridge in the state of Washington in 1940?

A

Every object has its natural frequency that will lead to resonance. The bridge was destroyed by fairly week wind because the resonance of the wind matched the resonance of the bridge.

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20
Q

Why is the Moon described as a “silent planet”?

A

No atmosphere on the moon.

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21
Q

Electromagnetic waves consist of
A. high-frequency sound waves.
B. particles of light energy.
C. compressions and rarefactions of electromagnetic pulses.
D. oscillating electric and magnetic fields.

A

D
Not C because electromagnetic is a transverse wave, not longitudinal.

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22
Q

What is it, exactly, that waves in a light wave? What produces an electromagnetic wave?

A

Any accelerated charge

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23
Q

Which has the shorter wavelengths, ultraviolet or infrared? Which has the higher frequencies?

A

Ultraviolet for both

24
Q

What is the principal difference between a gamma ray and an infrared ray?

A

Frequency or wavelengths

25
Q

You can get a sunburn on a cloudy day, but you can’t get a sunburn even on a sunny day if you are behind glass. Explain.

A

Sunburns come from ultraviolet light. Ultraviolet radiation can travel through the clouds but not glass. Glass is opaque for ultraviolet.

26
Q

Your friend says that any radio wave travels appreciably faster than any sound wave. Do you agree or disagree, and why?

A

I agree because radio waves travels with the speed of light.

27
Q

Which travels with the greatest speed in a vacuum?
A. radio waves
B. gamma rays
C. light waves
D. X-rays
E. all have the same speed

A

E

28
Q

Which of these electromagnetic waves have the shortest wavelength?

A. radio waves
B. infrared waves
C. light waves
D. ultraviolet waves
E. X-rays

A

E

29
Q

Does color television operate by color addition or by color subtraction? Defend your answer.
In which of these cases will a ripe banana appear black?

A

TV: addition
Banana: subtraction, illuminate the banana with a light that doesn’t have yellow, no red or green, use a blue light

30
Q

Green light + _______ light = white light

A

Magenta

31
Q

Yellow light + blue light = _______ light

A

White because red + green + blue = white

32
Q

Magenta + yellow + cyan = _______ light

A

White

33
Q

Why can’t we see stars in the daytime?

A

Air molecules in the atmosphere scatters the light from the sun and the glow it creates is brighter than the stars.

34
Q

Why the sky is blue? Sun yellow or red?

A

Sky: the air molecules in the atmosphere are most effective at scattering blue light from the sun
Sun: the sun produces white light and appears white at zenith, when it is closer to the horizon, blue and green are taken out and left with yellow; when it is further down the horizon, blue, green and yellow is taken out and red is left

35
Q

Does a single raindrop illuminated by sunlight deflect light of a single color or does it disperse a spectrum of colors? Does it do this by reflection, refraction, or both?

A

Yes, by both; double refraction, single reflection

36
Q

What is the color of the peak frequency of solar radiation when it is plotted versus wavelength?

A

Green

37
Q
  1. What are the subtractive primary colors?
    A. Magenta, cyan, and yellow
    B. Red, yellow, and blue
    C. Magenta, cyan, and violet
    D. Red, green, and blue
A

A

38
Q

What is a radiation curve?

A

Plotting intensity/energy of a light on y axis vs wavelength on x axis

39
Q

The image in a pinhole camera is…

A

Inverted, real because it is projected, always in focus, size changes based on distance of screen and object

40
Q

In a converging lens, objects infinitely far away are focused…

A

The image will be produced at focal distance

41
Q
  1. Distinguish between a converging lens and a diverging lens. What kind of lens can be used to produce a real image? A virtual image?
A

Only a converging lens can create a real image.

Diverging lens create tiny, virtual images

42
Q

True/False: The Sun’s spectrum, as observed from Earth, is classified as absorption.

A

True

43
Q
  1. The graph at right shows the blackbody spectra for three different stars. Which of the stars is at the highest temperature?
    A. Star A
    B. Star B
    C. Star C
A

A. because it has the smallest lambda/wavelength

44
Q
  1. The presence of dark lines in the solar spectrum, the so-called Fraunhofer lines, means that
    A. Radiation from the Sun’s interior is dissociating (breaking apart) molecules in the Sun’s atmosphere.
    B. A hotter layer of gas overlies the cooler layers of the solar atmosphere.
    C. A cooler layer of gas overlies the deeper, hotter layers of the solar atmosphere.
    D. Interplanetary gases have absorbed light at specific wavelengths.
A

C

45
Q
  1. The spectrum observed is:

A. Continuous
B. Absorption
C. Emission
D. Dispersion

A

B
Just light is continuous
No light is emission

46
Q
  1. What is refraction of light?
    A. The change in direction of a light ray as it reflects from a denser material than the one in which it is traveling
    B. The absorption of light as it traverses a dense, transparent material
    C. The breaking of white light into its composite colors
    D. The change in direction of light as it crosses the boundary between different transparent materials.
A

A. Reflection
B. Absorption
C. Dispersion
D. Refraction

47
Q

Red light is characterized by a wavelength of approximately:
A. 400 nm B. 500 nm
C. 600 nm D. 700 nm

A

D. 700 nm

48
Q

True/False: True or False: Different colors of light are waves with different amplitudes.

A

False

49
Q
  1. The two kinds of electromagnetic radiation that can easily be observed through the Earth’s atmosphere are:
    A. visible (optical) and ultraviolet.
    B. visible (optical) and infrared.
    C. ultraviolet and infrared.
    D. visible (optical) and radio.
A

D. Visible light, radio light

50
Q

The hottest stars are..
A. Blue B. Red
C. Yellow D. White

A

A. Blue

51
Q

True or False: A red giant star appears red because it is a very hot star.

A

False, it would be a cool giant

52
Q
  1. How does the speed of radio waves compare to the speed of visible light in vacuum?
    A. Radio waves are much slower
    B. They both travel at the same speed
    C. Radio waves are much faster
    D. Cannot be answered without knowing the wavelength
A

B

53
Q
  1. Atoms of different elements have unique spectral lines because each element
    A. has atoms of a unique color
    B. has a unique set of electron orbitals
    C. has unique photons
    D. none of the above, spectral lines are not unique to each type of atom
A

B

54
Q
  1. What causes light from a star to be Doppler-shifted?
    A. the distance between us and a star
    B. the gas and the dust between us and the star
    C. the speed of the star toward or away from us
    D. temperature differences between us and the star equal to +4.8 mag
A

C

55
Q
  1. The chemical makeup of the Sun’s surface can be determined by:
    A. taking a sample of the star’s surface with a space probe.
    B. examining the chemicals present in a meteorite because it is part of the solar system.
    C. measuring the components of the solar wind with Earth-orbiting spacecraft.
    D. solar spectroscopy
A

D

56
Q

Compared to visible light, infrared light has:
A. higher energy and longer wavelength
B. lower energy and longer wavelength
C. lower energy and shorter wavelength
D. higher energy and shorted wavelength

A

B

57
Q

What is the wavelength of the carrier wave of a campus radio station, broadcasting at a frequency of 97.2 MHz (million cycles or second or million Hertz)

A

Astrophysics (2 decks)

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