Of the first exoplanets found, most were detected by:
A) noting the drop in the star's light as the planet transits its disk.
B) imaging them with the HST in the infrared, where they are easier to stop.
C) noting the Doppler shifts of the star as the planet orbits it from side to side.
D) receiving radio transmissions from them, much like Jupiter emits.
E) detecting the oxygen in their atmospheres spectroscopically.
C
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Pluto's density is 1.8 g/cm3 . Iron is about 5 g/cm3 . Rock is about 3 g/cm3 . Ice or water is 1.0 g/cm3 . This implies that
a. Pluto has a large iron-nickel core. b. Pluto is about 35% water ice and 65% rocky material. c. Pluto is all rock. d. Pluto is all water or water ice.
A very long string is tied to a rigid wall at one end while the other end is attached to a simple harmonic oscillator. Which of the following can be changed by changing the frequency of the oscillator?
a. The speed of the waves traveling along the string. b. The tension in the string. c. The wavelength of the waves on the string. d. All of the above. e. None of the above.
Which of the following statements is correct?
a. You only need to know the amount of thermal energy a body contains to calculate its temperature. b. The temperature of a body is directly proportional to the amount of work the body has performed. c. The quantity of thermal energy exchanged by two bodies in contact is inversely proportional to the difference in their temperatures. d. The quantity of thermal energy exchanged by two bodies in contact is directly proportional to the difference in their temperatures. e. Different amounts of thermal energy are transferred between two bodies in contact if different temperature scales are used to measure the temperature difference between the bodies.
Nanostructured materials can have unique properties. For materials with dimensions measured in nanometers the amount of surface energy is comparable to the bonding energy in the material.
(a) Compare the magnitude of the total surface energy to the total bond energy for a sphere of Ni atoms with one atom at the center surrounded by twelve nearest neighbors. The surface energy of Ni is 1.90 J/m2, the cohesive energy of Ni is –4.435 eV/atom, and the lattice parameter of FCC Ni is 0.352 nm. Assume that the total radius of this sphere is equal to 1 atomic diameter. (b) Is this 13-atom cluster of atoms stable?