waves and particles-solutions - scribner(eks662 waves and...

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scribner (eks662) – waves and particles – yeazell – (55745)1Thisprint-outshouldhave16questions.Multiple-choice questions may continue onthe next column or page – find all choicesbefore answering.00110.0pointsWe know that a lamp filament at 2500 Kradiates white light.Does the lamp filament also radiate energywhen it is at room temperature?003(part1of2)10.0pointsThe cosmic background radiation is that of ablack body at 2.7 K.What is the valueλmaxat which the distri-bution has a maximum?1.No; the filament will be dark at roomtemperature.2.No; the filament will have the same tem-perature as its environment.3.Yes; the filament will be at a temperaturethat is greater than absolute zero.correct4.Yes; the filament has a smaller heat ca-pacity than its environment.Explanation:A large filament or any object emits radia-tion at all temperatures greater than absolutezero.The peak freqency of this radiation isproportional to the absolute temperature ofthe object.At room temperature this fre-quency is in the far infrared part of the spec-trum and therefore cannot normally be seen.When the temperature of the filament is in-creased, more of the radiation moves into thevisible part of the spectrum and we see light.
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10.0pointsIf we continue heating a piece of initiallyroom-temperaturemetalinadarkroom,what will be its first visible color?1.There will be no color at all.2.Violet3.White4.RedcorrectExplanation:Themetalglowsatalltemperatures,whether we see the glow or not. As its temper-ature is increased, the glow reaches the visiblepart of the spectrum and is visible to humaneyes. Light of the lowest energy per photon isred, so the heated metal passes from infra-red(which we cannot see) to visible red.keywords:003(part1of2)10.0pointsThe cosmic background radiation is that of ablack body at 2.7 K.What is the valueλmaxat which the distri-bution has a maximum?

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