Matter Waves: The spacing of the atoms of a crystal is 159 pm. A monoenergetic beam of neutrons directed normally at the surface of the crystal undergoes first order diffraction at an angle of 58° from the normal. What is the energy of each of the neutrons? (mneutron = 1.675 × 10-27 kg, 1 eV = 1.6 × 10-19 J, h = 6.626 × 10-34 J ? s)
A. 0.045 eV
B. 0.039 eV
C. 0.050 eV
D. 0.056 eV
E. 0.061 eV
Answer: A
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Answer the following statement true (T) or false (F)
A pilot executes a vertical dive. Just before the plane starts to come up from the bottom of the dive, the force on him is
A) more than g, and pointing down. B) less than g, and pointing up. C) more than g, and pointing up. D) less than g, and pointing down. E) equal to g, and pointing down.
When an object is placed 60. cm from a converging lens, it forms a real image. When the object is moved to 40. cm from the lens, the image moves 10. cm farther from the lens. What is the focal length of the lens?
A) 42. cm B) 50. cm C) 40. cm D) 20. cm E) 30. cm
What is the meaning of the expression ?F = 0?
What will be an ideal response?