A ruby laser delivers a 2.28-J pulse in approximately 50 nanoseconds. The wavelength of the light is 694.4 nm. At least how many atoms within the ruby rod had to be excited to allow this high-energy laser pulse? (h = 6.63 × 10^-34 J×s, c = 3.00 × 10^8 m/s, 1 eV = 1.6 × 10^-19 J, and 1 nm = 10-9 m)
a. 3 × 10^19
c. 8 × 10^18
b. 4 × 10^18
d. 6 × 10^20
C
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Which of the following statements is true of the first reaction in the proton-proton chain?
A) It yields a helium atom. B) It emits a positron. C) It emits a gamma ray. D) It yields carbon dioxide.
The apparent visual magnitude difference between two stars is 10 and thus the approximate intensity ratio is 10,000
a. True b. False Indicate whether the statement is true or false
What is the effect of adding some boron on how easily a silicon crystal conducts electricity?
A. The crystal becomes more conductive. B. The crystal becomes less conductive. C. The boron creates new energy levels for electrons but does not change the crystal’s conductivity.
The Earth's gravity exerts no torque on a satellite orbiting the Earth in an elliptical orbit. Compare the motion of the satellite at the point nearest the Earth (perigee) to the motion at the point farthest from the Earth (apogee). At these two points:
a. the tangential velocities are the same. c. the angular momenta are the same. b. the angular velocities are the same. d. the kinetic energies are the same.