As you may well know, placing metal objects inside a microwave oven can generate
ID: 1409500 • Letter: A
Question
As you may well know, placing metal objects inside a microwave oven can generate sparks. Two of your friends are arguing over the cause of the sparking, with one stating that the microwaves "herd" electrons into "pointy" areas of the metal object, from which the electrons jump from one part of the object to another. The other friend says that the sparks are caused by the photoelectric effect. In this problem, we will prove or disprove the latter idea using basic physics. Suppose the typical work function of the metal is roughly 3.420 × 10-19 J (2.135 eV). Calculate the maximum wavelength in angstroms of the radiation that will eject electrons from the metal. Part 2) Considering that microwave ovens radiate at 2.45 GHz, how would you respond to the debate? A)The sparks cannot be caused by the photoelectric effect. B)The sparks could be caused by the photoelectric effect.
Explanation / Answer
work function is the minimum energy ewquired to eject the electron
energy = planks constant * speed of light / wavelength
3.42 * 10^-19 = 6.626 * 10^-34 * 3 * 10^8 / wavelength
maximum wavelength= 5.81228 * 10^-7 m or 5812.28 angstroms
energy = planks constant * frequenccy
energy = 6.626 * 10^-34 * 2.45 * 10^9
energy = 1.62337 10^-24 J
which is less than work function so
The sparks cannot be caused by the photoelectric effect
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