Radioactive Decay: A test tube of an isotope having a decay constant of 0.765 × 10-6 s-1 contains 3.0 × 1017 nuclei of this isotope.(a) What is the half-life of this isotope?(b) What is the initial activity (in Bq) of the isotope?(c) What is the activity of the isotope after 12 days?
What will be an ideal response?
(a) 9.06 × 105 s (b) 2.3 × 1011 Bq (c) 1.0 × 1011 Bq
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Photoelectric Effect: The work function of a certain metal is 1.90 eV. What is the longest wavelength of light that can cause photoelectron emission from this metal? (1 eV = 1.60 × 10-19 J, c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s)
A. 231 nm B. 14.0 nm C. 62.4 nm D. 344 nm E. 654 nm
For a diverging lens with one flat surface, the radius of curvature for the curved surface is 25.0 cm. What must the index of refraction be so that the focal length is –17.0 cm?
a. 0.680 b. 1.68 c. 2.47 d. 1.74 e. 1.47
John says that the value of the function cos[w(t + T) + j], obtained one period T after time t, is greater than cos(wt + j) by 2p. Larry says that it is greater by the addition of 1.00 to cos(wt + j). Which one, if either, is correct?
a. John, because wT = 2p. b. John, because wT = 1 radian. c. Larry, because wT = 2p. d. Larry, because wT = 1 radian. e. Neither, because cos(q + 2p) = cosq.
A scientific hypothesis can be disproved with
A) one reproducible experiment. B) disapproval of other scientists. C) many tests by many scientists. D) philosophical reasoning.