A thermos bottle works well because:
A. its glass walls are thin
B. silvering reduces convection
C. vacuum reduces heat radiation
D. silver coating is a poor heat conductor
E. none of the above
Ans: E. none of the above
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The best filter to remove the K? x-rays from a Mo x-ray tube that have a wavelength of 0.06322 nm but that transmits the K? x-rays of wavelength 0.0711 nm is
(a) Nb with a K edge of 0.06529 nm (b) Mo with a K edge of 0.06198 nm (c) Y with a K edge of 0.07276 nm (d) Ru with a K edge of 0.05605 nm
Part of the current atmosphere of Earth is believed to be
a. the remnants of the original hydrogen and helium gas from the solar nebula attracted by the protoplanet. b. the result of the melting and vaporizing of the glaciers from the last ice age. c. composed primarily of hydrogen and helium. d. composed of gases that were outgassed from the heated rocks sometime after the planet formed. e. the result of a collision between the Sun and another star.
The length of a certain wire is doubled while its radius is kept constant. What is the change in the resistance of this wire?
A) It stays the same. B) It is doubled. C) It is tripled. D) It is quadrupled. E) It is reduced by a factor of 2.
Which of the following particles are leptons? (There may be more than one correct choice.)
A) protons B) neutrons C) electrons D) photons E) quarks