How is 21 cm radiation produced?
What will be an ideal response?
When the electron orbiting the proton for hydrogen flips its spin, the energy radiated has a wavelength of 21 cm., and is detected with radio telescopes.
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What happens to the surface temperature and luminosity when a protostar undergoes convective contraction?
A) Its surface temperature and luminosity increase. B) Its surface temperature remains the same and its luminosity decreases. C) Its surface temperature and luminosity decrease. D) Its surface temperature decreases and its luminosity increases. E) Its surface temperature and luminosity remain the same.
What is the energy of a photon that, when it is absorbed by a hydrogen atom, excites an electron from the ground state of the hydrogen atom to the n = 2 state?
A) 10.2 eV B) 1.63 × 10-18 J C) 1.63 × 10-18 Nm D) All of the answers are correct. E) None of the answers is correct.
A 30.0-kg object experiences a drag force due to air resistance with a magnitude proportional to the square of its speed. The object falls with an acceleration of 4.00 m/s2 downward when it is falling downward at 70.0 m/s. What is its terminal speed?
A) 110 m/s B) 157 m/s C) 91.0 m/s D) 172 m/s E) 108 m/s
If the work function of a metal surface is 2.20 eV, what frequency of incident light would give a maximum kinetic energy of 0.25 eV to the photoelectrons ejected from this surface? (1 eV = 1.60 × 10-19 J, h = 6.626 × 10-34 J ? s)
A) 2.50 × 1014 Hz B) 3.53 × 1014 Hz C) 5.92 × 1014 Hz D) 2.05 × 1014 Hz E) 1.02 × 1014 Hz