A helium-neon laser emits red light having a wavelength of 6.4 × 10^?7 m and a power of 0.5 mW. How many photons are emitted each second?
a. 6.4 × 10^38
b. 1.6 × 10^21
c. 3.2 × 10^25
d. 2.6 × 10^18
e. 1.6 × 10^15
e
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A 2.0 kg object is moving at a velocity of 12.0 m/s. The drag force 6.0 N. If the drag force is given by the equation F = 
then the value of b is
a. 
b. 
c. 
d. 
e. 
While many elemental spectral lines are visible, almost all molecular lines lie in the ________ portion of the spectrum, since they are at much lower energy
A) infrared B) radio C) X-ray D) ultraviolet E) visible light
The assumption of homogeneity states that
a. the Universe looks the same at all epochs. b. the Universe looks the same from all locations over sufficiently great distances. c. the Universe looks the same in all directions over sufficiently great distances. d. the Universe looks the same at all epochs, the Universe looks the same from all locations over sufficiently great distances, and the Universe looks the same in all directions over sufficiently great distances. e. None of the other choices are correct.
Electron A is fired horizontally with speed 1.00 Mm/s into a region where a vertical magnetic field exists. Electron B is fired along the same path with speed 2.00 Mm/s. Which electron has a larger magnetic force exerted on it?
1.A does. 2.B does. 3.The forces have the same nonzero magnitude. 4.The forces are both zero.