977_Physics ProblemsTechnical Physics

977_Physics ProblemsTechnical Physics - 318 The Nature of...

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318 The Nature of Light and the Laws of Geometric Optics Q35.16 Light coming up from underwater is bent away from the normal. Therefore the part of the oar that is submerged appears bent upward. Q35.17 Highly silvered mirrors reflect about 98% of the incident light. With a 2-mirror periscope, that results in approximately a 4% decrease in intensity of light as the light passes through the periscope. This may not seem like much, but in low-light conditions, that lost light may mean the difference between being able to distinguish an enemy armada or an iceberg from the sky beyond. Using prisms results in total internal reflection, meaning that 100% of the incident light is reflected through the periscope. That is the “total” in total internal reflection. Q35.18 Sound travels faster in the warmer air, and thus the sound traveling through the warm air aloft will refract much like the light refracting through the nonuniform sugar-water solution in Question 35.10. Sound that would normally travel up over the tree-tops can be refracted back towards the
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