Concept explainers
The reason for which the electrons left in the metals in an ordinary room without undergoing
Answer to Problem 1CQ
The threshold wavelength for photoelectric effect to take place is generally shorter than the
Explanation of Solution
In photoelectric effect, electrons are ejected from certain metallic surfaces as the
In an ordinary room atmosphere, the ambient light is in the visible range, which have wavelength higher than the threshold wavelength. Thus, the energy of the incident photons of visible spectrum cannot knock out electrons due to the lack of sufficient energy. Moreover, the oxide layers and other coatings on the surface of the metal often hinder the interaction of the incident light and the electrons in the metal surface. These are the reasons for which the electrons left in the metals in an ordinary room without undergoing photoelectric effect
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Chapter 28 Solutions
College Physics (10th Edition)
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- Estimate the binding energy of electrons in magnesium, given that the wavelength of 337 nm is the longest wavelength that a photon may have to eject a photoelectron from magnesium photoelectrode.arrow_forwardA Thomson-type experiment with relativistic electrons. One of the earliest experiments to show that p = mv (rather than p = mv) was that of Neumann. [G. Neumann, Ann. Physik 45:529 (1914)]. The apparatus shown in Figure P4.5 is identical to Thomsons except that the source of high-speed electrons is a radioactive radium source and the magnetic field B is arranged to act on the electron over its entire trajectory from source to detector. The combined electric and magnetic fields act as a velocity selector, only passing electrons with speed v, where v = V/Bd (Equation 4.6), while in the region where there is only a magnetic field the electron moves in a circle of radius r, with r given by p = Bre. This latter region (E = 0, B = constant) acts as a momentum selector because electrons with larger momenta have paths with larger radii. (a) Show that the radius of the circle described by the electron is given by r = (l2 + y2)/2y. (b) Typical values for the Neumann experiment were d = 2.51 104 m, B = 0.0177 T, and l = 0.0247 m. For V = 1060 V, y, the most critical value, was measured to be 0.0024 0.0005 m. Show that these values disagree with the y value calculated from p = mv but agree with the y value calculated from p = mv within experimental error. (Hint: Find v from Equation 4.6, use mv = Bre or mv = Bre to find r, and use r to find y.) Figure P4.5 The Neumann apparatus.arrow_forward(a) What is the momentum of a 0.0100-nm-wavelength photon that could detect details of an atom? (b) What is its energy in MeV?arrow_forward
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