The activity of a sample reduces from 7.55 × 109 Bq to 5.11 × 109 Bq in 5.50 months
(a) What is the half life?
(b) How many months must one wait for the activity to decrease to 10%?
(a) 9.77 months
(b) 32.4 months
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Determine
(a) For copper, determine the energies at which the probability of electron occupation is 0.9 and 0.1 at 300 K. (b) Are these energies symmetric about the Fermi energy of 7.04 eV?
Which of the following general statements about light and Earth's atmosphere is not true?
A) X-rays from the Sun are absorbed in the thermosphere. B) Visible light from the Sun is absorbed in the exosphere. C) Ultraviolet from the Sun is absorbed in the stratosphere. D) Infrared light emitted by Earth itself is absorbed in the troposphere.
A neutral atom always contains
a. the same number of protons as it does neutrons. b. the same number of electrons as it does neutrons. c. the same number of protons as it does electrons. d. twice as many protons as it does neutrons. e. twice as many neutrons as it does protons.
Consider a situation where you exert a force F on a crate of mass m, moving it at a speed v a distance d across a floor in a time interval t. The quantity 1/2 mv2 is
a. the kinetic energy of the crate b. the potential energy of the crate c. the linear momentum of the crate d. the work you do on the crate e. the power you supply to the crate