Q&A Hero

Q: According to Wein's law, the wavelength of the peak energy will be ________ if the temperature of the blackbody is doubled.

Q: Stars that appear blue or white in color are ________ than our yellow Sun.

Q: A featureless spectrum, such as a rainbow, is said to be ________.

Q: In electromagnetic waves, the electric and magnetic fields vibrate ________ to each other.

Q: An FM station broadcasts at a frequency of 100 MHz. The wavelength of its carrier wave is ________.

Q: A wave with a frequency of 2 Hz will have a period of ________.

Q: A frequency of one hundred ________ means the wave is vibrating one hundred million times per second; this is a typical carrier frequency for FM (frequency modulation) radio.

Q: A wave with a period of .01 seconds has a frequency of ________ Hz.

Q: The product of the wavelength times the frequency of a wave is its ________.

Q: The distance from a wave's crest to its undisturbed position is the ________.

Q: According to the Zeeman effect, the splitting of a sunspot's spectral lines is due to A) their rapid rotation. B) temperature variations. C) their magnetic fields. D) their radial velocity. E) a Doppler shift.

Q: If the rest wavelength of a certain line is 600 nm, but we observe it at 594 nm, then A) the source is approaching us at 1 % of the speed of light. B) the source is approaching us at 0.1 % of the speed of light. C) the source is receding from us at 10% of the speed of light. D) the source is getting 1% hotter as we watch. E) the source is spinning very rapidly, at 1% of the speed of light.

Q: If a source of light is approaching us at 3,000 km/sec, then all its waves are A) blue shifted by 1%. B) red shifted by 1%. C) not affected, as c is constant regardless of the direction of motion. D) blue shifted out of the visible spectrum into the ultraviolet. E) red shifted out of the visible into the infrared.

Q: The observed spectral lines of a star are all shifted towards the red end of the spectrum. Which statement is true? A) This is an example of the photoelectric effect. B) This is an example of the Doppler effect. C) The second law of Kirchhoff explains this. D) The star is not rotating. E) The star has a radial velocity towards us.

Q: For hydrogen, the transition from the first to third excited state produces A) a red emission line. B) a blue green absorption line. C) a violet emission line. D) an infrared line. E) an ultraviolet line.

Q: In a hydrogen atom, a transition from the 2nd to the 1st excited state will produce A) the bright red Balmer alpha emission line. B) no emission line. C) a dark absorption line. D) an ultraviolet spectral line. E) three different emission lines.

Q: Electromagnetic radiation A) can only travel in a dense medium. B) has only the properties of waves. C) can behave both as a wave and as a particle. D) is the same as a sound wave. E) has nothing in common with radio waves.

Q: In general, the spectral lines of molecules are A) more complex than those of atoms. B) the same as the atoms they contain. C) only absorption lines. D) less complex than those of atoms. E) nonexistent.

Q: In Bohr's model of the atom, electrons A) only make transitions between orbits of specific energies. B) are not confined to specific orbits. C) are spread uniformly through a large, positive mass. D) can be halfway between orbits. E) move from one orbit to the next orbit in many small steps.

Q: Which of these is emitted when an electron falls from a higher to lower orbital? A) another electron B) a positron C) a neutrino D) a photon E) a graviton

Q: A jar filled with gas is placed directly in front of a second jar filled with gas. Using a spectroscope to look at one jar through the other you observe dark spectral lines. The jar closest to you contains A) the hotter gas. B) the cooler gas. C) gas at the same temperature as the other jar. D) the exact same gas as the other jar. E) gas at very high pressure.

Q: The element first found in the Sun's spectrum, then on Earth 30 years later, is A) hydrogen. B) helium C) solarium. D) technicum. E) aluminum.

Q: The Sun's observed spectrum is A) a continuum with no lines, as shown by the rainbow. B) a continuum with emission lines. C) only absorption lines on a black background. D) a continuum with absorption lines. E) only emission lines on a black background.

Q: If a star was the same size as our Sun, but was 81times more luminous, it must be A) twice as hot as our Sun. B) three times hotter than the Sun. C) four times hotter than the Sun. D) nine times hotter than the Sun. E) 81 times hotter than the Sun.

Q: Increasing the temperature of a blackbody by a factor of 3 will increase its energy by a factor of A) 3 B) 6 C) 9 D) 12 E) 81

Q: The total energy radiated by a blackbody depends on A) the fourth power of its temperature. B) the square of its temperature. C) the square root of its temperature. D) the fourth root of its temperature. E) the cube of its temperature.

Q: What is the name of the temperature scale that places zero at the point where all atomic and molecular motion ceases? A) Fahrenheit B) Celsius C) Kelvin D) Centigrade E) Ransom

Q: What is true of a blackbody? A) It appears black to us, regardless of its temperature. B) Its energy is not a continuum. C) Its energy peaks at the wavelength determined by its temperature. D) If its temperature doubled, the peak in its radiation curve would be doubled in wavelength. E) It has a complete absence of thermal energy.

Q: In the Kelvin scale, absolute zero lies at A) zero K. B) 273 degrees C C) -373 degrees C. D) Both A and B are correct. E) Both A and C are correct.

Q: Medium A blocks more of a certain wavelength of radiation than medium B. Medium A has a higher A) transparency. B) seeing. C) clarity. D) opacity. E) albedo.

Q: The radiation our eyes are most sensitive to is the color A) red at 6563 Angstroms. B) yellow-green at about 550 nm. C) violet at 7,000 Angstroms. D) blue at 4,321 nm. E) black at 227 nm.

Q: The two forms of electromagnetic (E-M) radiation that experience the least atmospheric opacity are A) visible light and radio waves. B) visible light and infrared waves. C) microwaves and radio waves. D) X and gamma radiation. E) ultraviolet and infrared waves.

Q: Which of these is the same for all forms of electromagnetic (E-M) radiation in a vacuum? A) amplitude B) wavelength C) frequency D) speed E) photon energy

Q: The speed of light in a vacuum is A) 300,000 km/sec. B) 768 km/hour. C) 186,000 miles per hour. D) h = E/c. E) not given.

Q: If a wave's frequency doubles and its speed stays constant, its wavelength A) is halved. B) is also doubled. C) is unchanged, as c is constant. D) is now 4 longer. E) becomes 16 longer.

Q: Consider this diagram. Which statement is true? A) The amplitude is 4 and the wavelength is 6. B) The amplitude is 6 and the wavelength is 4. C) The amplitude is 8 and the wavelength is 6. D) The amplitude is 4 and the wavelength is 12. E) The amplitude is 8 and the wavelength is 12.

Q: A wave's velocity is the product of the A) frequency times the period of the wave. B) period times the energy of the wave. C) amplitude times the frequency of the wave. D) frequency times the wavelength of the wave. E) amplitude times the wavelength of the wave.

Q: Which of these is not a form of electromagnetic radiation? A) DC current from your car battery B) light from your camp fire C) X-rays in the doctor's office D) ultraviolet causing a suntan E) radio signals

Q: The Doppler effect can reveal the rotation speed of a star by the splitting of the spectral lines.

Q: Spectroscopy of a star can reveal its temperature, composition, and line-of-sight motion.

Q: You would perceive a change in a visible light wave's amplitude as a change in its color.

Q: If a fire truck's siren is rising in pitch, it must be approaching us.

Q: The larger the red shift, the faster the distant galaxy is rushing toward us.

Q: In the Doppler effect, a red shift of spectral lines shows us the source is receding from us.

Q: The broader the spectral line, the higher the pressure of the gas that is creating it.

Q: The Zeeman effect reveals the presence of strong magnetic fields by the splitting of spectral lines.

Q: When an electron in a hydrogen atom drops from the second to the first excited energy state it emits a bright red emission line called hydrogen alpha.

Q: In the Bohr model of the atom, an electron can only exist in specific, well-defined energy levels.

Q: Spectral lines are produced when an electron makes a transition from one energy state to another.

Q: The shorter a wave's wavelength, the greater its energy.

Q: An emission line results from an electron falling from a higher to lower energy orbital around its atomic nucleus.

Q: An absorption line spectrum, with dark lines crossing the rainbow of the continuum, is produced by a low-density hot gas.

Q: The spectral lines of each element are distinctive to that element, whether we are looking at emission or absorption lines.

Q: As a star's temperature increases, the frequency of peak emission also increases.

Q: Doubling the temperature of a blackbody will double the total energy it radiates.

Q: According to Wein's law, the higher the surface temperature of a star, the redder its color.

Q: A blue star has a higher surface temperature than a red star.

Q: According to Wein's law, the larger the blackbody, the shorter its peak wavelength.

Q: In blackbody radiation, the energy is radiated uniformly in every region of the spectrum, so the radiating body appears black in color.

Q: Observations in the X-ray portion of the spectrum are routinely done from the surface of the Earth.

Q: As white light passes through a prism, the red (longer) wavelengths bend less than the blue (shorter) wavelengths, so forming the rainbow of colors.

Q: Wave energy can only be transmitted through a material medium.

Q: As they move through space, the vibrating electrical and magnetic fields of a light wave must move perpendicular to each other.

Q: Changing the electric field will have no effect on the magnetic fields of a body.

Q: While gravity is always attractive, electromagnetic forces are always repulsive.

Q: The greater the disturbance of the medium, the higher the amplitude of the wave.

Q: If a new wave arrives on shore every two seconds, then its frequency is 2 Hz.

Q: The frequency of a water wave gives us its height.

Q: Radio waves, visible light, and X-rays are all types of electromagnetic radiation.

Q: Explain how the Doppler Effect has been used to detect invisible planets orbiting other Sun-like stars.

Q: How can the Doppler Effect be used to determine if a storm is forming into a tornado?

Q: Give and explain an example of the use of the Doppler Effect on the highway.

Q: Give an example of the Doppler Effect being used in a baseball game.

Q: Why do we know that the red Balmer emission line in hydrogen represents a smaller quantum leap than the violet line?

Q: How does the energy of a water wave differ from the energy of a photon?

Q: Explain the appearance of the Sun's spectrum, as noted by Fraunhofer.

Q: How does Stefan's law and a knowledge of Earth's history tell us that the Sun's temperature cannot have varied much in the last 3.5 billion years?

Q: Why would a hotter star appear blue-white while a cooler star appear red or not be visible at all?

Q: How can Wein's law be used to determine the temperature of a star?

Q: Contrast the speeds of sound and light in watching a flash of lightning, then listening for the thunder to follow.