ism_chapter_31 - Chapter 31 Properties of Light Conceptual...

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873 Chapter 31 Properties of Light Conceptual Problems 1 Determine the Concept The population inversion between the state E 2,Ne and the state 1.96 eV below it (see Figure 31-9) is achieved by inelastic collisions between neon atoms and helium atoms excited to the state E 2,He . 2 •• Determine the Concept Although the excited atoms emit the light of the same frequency on returning to the ground state, the light is emitted in a random direction, not exclusively in the direction of the incident beam. Consequently, the beam intensity is greatly diminished. 3 Determine the Concept The layer of water greatly reduces the light reflected back from the car’s headlights, but increases the light reflected by the road of light from the headlights of oncoming cars. 4 Determine the Concept When light passes from air into water its wavelength changes ( water air water n λ = ), its speed changes ( water water n c v = ), and the direction of its propagation changes in accordance with Snell’s law. correct. is ) ( c *5 •• Determine the Concept The change in atmospheric density results in refraction of the light from the sun, bending it toward the earth. Consequently, the sun can be seen even after it is just below the horizon. Also, the light from the lower portion of the sun is refracted more than that from the upper portion, so the lower part appears to be slightly higher in the sky. The effect is an apparent flattening of the disk into an ellipse. 6 Determine the Concept ( a ) Yes. ( b ) Her procedure is based on Fermat’s principle in that, since the ball presumably travels at constant speed, the path that requires the least time of travel corresponds to the shortest distance of travel. 7 Determine the Concept Because she can run faster than she can swim, she should choose the path that will maximize her running distance. Path LES is the path that satisfies this criterion.
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Chapter 31 874 8 Picture the Problem The intensity of the light transmitted by the second polarizer is given by , I I θ 2 0 trans cos = where . 2 1 0 I I = Therefore, 2 2 1 trans cos I I = and correct. is ) ( b 9 Picture the Problem Polarized light can be produced from unpolarized light by absorption, reflection, birefringence, and scattering. Therefore, correct. is ) ( d *10 •• Determine the Concept The diagram shows that the radiated intensity for a dipole is zero in the direction of the dipole moment. Because the dipole axis is in the same direction as the polarization, for light polarized parallel to plane of incidence, the dipole axis will point in the same direction as the reflected wave, i.e., in the direction described by Brewster’s law. As the diagram indicates, there is zero field in the direction of the refracted ray. On the other hand, if the incoming wave is polarized perpendicular to the plane of incidence, the dipole axis will never point along the direction of propagation for the reflected or refracted wave.
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This homework help was uploaded on 02/26/2008 for the course PHYSICS 11 taught by Professor Licini during the Spring '07 term at Lehigh University .

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ism_chapter_31 - Chapter 31 Properties of Light Conceptual...

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