Why are remote sites chosen for ground-based telescopes?
A. Populated areas produce light pollution that degrades the quality of observations.
B. Deserts and mountaintops tend to be cloud-free, making observations convenient.
C. Remote areas have less interference from power lines and other sources of noise.
D. Mountaintops allow astronomers to avoid morning hazes.
E. All of these choices are correct.
Answer: E
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Because the changes in energy levels happen in discrete steps, we refer to these as ________ leaps
Fill in the blank(s) with correct word
Captain Jirk reports to headquarters that he left the planet Senesca 1.88 × 10^4 seconds earlier. Headquarters sends back the message: "Was that spaceship proper time?" It will be spaceship proper time if it was
a. measured by one clock fixed at one spot on Senesca. b. measured by one clock fixed at one spot on the spaceship. c. measured by a clock on Senesca at departure and by a clock on the spaceship when reporting. d. measured by a clock on the spaceship when departing and by a clock on Senesca when reporting. e. calculated by dividing the distance from Senesca according to Senesca by the speed of the spaceship.
Pair production can occur if:
A) the energy of two photons is greater than the combined mass-energy of a particle-anti-particle pair. B) only virtual particles are produced. C) photons are at the event horizon of a black hole. D) one particle is struck by a sufficiently high energy photon that a pair of electrons is formed. E) the particle and antiparticle have opposite spins.