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Chapter 1: Q10PE (page 11)
An infant鈥檚 pulse rate is measured to be . What is the percent uncertainty in this measurement?
The percentage uncertainty in the given case is 3.846%.
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(a) An excimer laser used for vision correction emits193 - nm UV. Calculate the photon energy in eV.
(b) These photons are used to evaporate corneal tissue, which is very similar to water in its properties. Calculate the amount of energy needed per molecule of water to make the phase change from liquid to gas. That is, divide the heat of vaporization in kJ/kg by the number of water molecules in a kilogram.
(c) Convert this to eV and compare to the photon energy. Discuss the implications.
Conversations with astronauts on the lunar surface were characterized by a kind of echo in which the earthbound person鈥檚 voice was so loud in the astronaut鈥檚 space helmet that it was picked up by the astronaut鈥檚 microphone and transmitted back to Earth. It is reasonable to assume that the echo time equals the time necessary for the radio wave to travel from the Earth to the Moon and back (that is, neglecting any time delays in the electronic equipment). Calculate the distance from Earth to the Moon given that the echo time was 2.56 s and that radio waves travel at the speed of light (\({\bf{3 \times 1}}{{\bf{0}}^{\bf{8}}}\;{\bf{m/s}}\)).
A person measures his or her heart rate by counting the number of beats in 30 s. If are counted in, what is the heart rate and its uncertainty in beats per minute?
Question: (a) Calculate the number of photoelectrons per second ejected from a \(1.00\,{\rm{m}}{{\rm{m}}^{\rm{2}}}\) area of sodium metal by \(500\,{\rm{nm EM}}\) radiation having an intensity of \(1.30\,{\rm{kW/}}{{\rm{m}}^{\rm{2}}}\) (the intensity of sunlight above the Earth鈥檚 atmosphere). (b) Given that the binding energy is\(2.28\,{\rm{eV}}\), what power is carried away by the electrons? (c) The electrons carry away less power than brought in by the photons. Where does the other power go? How can it be recovered?
If a marathon runner averages\({\bf{9}}.{\bf{5}}{\rm{ }}{{{\rm{mi}}} \mathord{\left/ {\vphantom {{{\rm{mi}}} {\rm{h}}}} \right. \\} {\rm{h}}}\), how long does it take him or her to run a\(26.22{\rm{ mi}}\)marathon?
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