Explain how "forbidden" lines appear in spectra of emission nebulae
What will be an ideal response?
These lines correspond to excited states that require a very long time to decay and emit a photon. In Earth labs, the gas density cannot be made low enough to allow this transition before a collision knocks the atom into another state. In the nebula, though, the density is so low that the transition has a chance to proceed.
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If the mixing of 10 atomic %copper into a silver crystal occurs at T=1000 K (727°C), determine the change in the Gibbs free energy on a per-mole basis if the enthalpy of solution for copper into silver is 0.25 eV/atom. (b) Based upon your result, should it be possible to mix 10 atomic %copper into silver? Explain your answer, and discuss this result in comparison to Example Problem 4.8.
What will be an ideal response?
Two fixed navigation beacons mark the approach lane to a star. The beacons are in line with the star and are 40 Mm apart. A spaceship approaches the star with a relative velocity of 0.30 c and passes the beacons
The passage of the ship between the beacons is timed by observers on the beacons. The time interval of the passage is closest to: A) 440 ms B) 470 ms C) 420 ms D) 250 ms E) 170 ms
Galileo observed which of the following phases of Venus?
A) full B) new C) crescent D) gibbous E) all of the above
Physical Pendulum: A simple pendulum that consists of a small ball of mass m and a massless wire of length L swings with a period T. Suppose now that the mass is rearranged so that mass of the ball was reduced but the mass of the wire was increased, with the total mass remaining m and the length being L. What is true about the new period of swing? (There could be more than one correct choice.)
A. The new period is T because the total mass m has not changed. B. The new period is T because the length L has not changed. C. The new period is greater than T. D. The new period is less than T. E. The new period is T because neither L nor m have changed.