A light-emitting diode has a power output of 0.3 W. If 590 nm is the average wavelength of the source, about how many photons are emitted per second? (h = 6.63 × 10^-34 J×s, c = 3.00 × 10^8 m/s, and 1 nm = 10-9 m)
a. 1021
c. 1018
b. 1025
d. 1029
C
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a. electrical forces between the protons b. alpha particles c. beta particles d. strong forces
A linear spring has a spring constant of 20 N/m. How far would it have to be stretched to have a potential energy of 0.10 J?
A) 0.10 m B) 200 m C) 0.0050 m D) 20 m E) 2.0 m
______________ is the major moon of Neptune
a. Triton b. Titan c. Ganymede d. Europa e. Callisto
the magnetic force on the proton 
A. The vector points in the +x direction. B. The vector points in the -x direction. C. The vector points in the +y direction. D. The vector points in the -y direction. E. The vector points in the +z direction. F. The vector points in the -z direction. T. The vector is zero.