The free-fall contraction of a molecular cloud
a. can be initiated by shock waves from supernovae.
b. can be initiated by nearby spectral type G stars.
c. can be initiated by the rotation of the cloud.
d. causes the cloud to become transparent to ultraviolet radiation.
e. causes the particles in the cloud to decrease the speed with which they move.
a
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The Doppler formula states that the ratio of the velocity of a source to the speed of light is equal to the ratio of the change in wavelength caused by the Doppler shift to the source wavelength, or A spacecraft has yellow headlights which radiate 600nm photons, and is travelling toward a stationary observer. If the spacecraft is travelling at a velocity of 1% of the speed of light (0.01c), what
will be the amount of the shift in wavelength observed (in nanometers)? What will be an ideal response?
An electron is projected horizontally with a speed of 
m exactly in the middle of two parallel plates at potentials of -40 V and 104 V, respectively. The plate separation distance is 3.0 cm. The plates are long enough that the proton, rather than passing completely between the plates, eventually strikes the plate sitting at 104 V potential. What is the speed of the proton when it strikes the plate? The mass of the electron is 
kg.
A. 
B. 
C. 
D. 
The focal length of a converging lens is
A. negative B. zero C. positive D. infinity
Find the energy of a photon whose frequency is 5 × 10^12 Hz