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標題: [Phy] [E2 Atomic World] Aurora Borealis are often observed in [打印本頁]

作者: bakhan.golden    時間: 2016-3-3 01:21 PM     標題: [E2 Atomic World] Aurora Borealis are often observed in

Aurora Borealis are often observed in skies at high latitudes. When energetic electrons from outerspace collide wit the oxygen atom in the upper atmosphere, the oxygen atoms are excited. The subsequent emission of light is usually green light of wavelength 558nm. The minimum speed of these energetic electrons is of order of magnitude ?
A. 10^(2) ms^(-1)
B. 10^(4) ms^(-1)
C. 10^(6) ms^(-1)
D. 10^(8) ms^(-1)
作者: yeungwk91    時間: 2016-3-3 01:48 PM

this Q requires approximation.

KE of electron = energy of the photon
作者: bakhan.golden    時間: 2016-3-3 02:03 PM

引用:
原帖由 yeungwk91 於 2016-3-3 01:48 PM 發表
this Q requires approximation.

KE of electron = energy of the photon
First, v=f入
Then, e=hf
Finally 0.5mv^2=hf

am i correct?
作者: yeungwk91    時間: 2016-3-3 02:04 PM     標題: 回覆 3# bakhan.golden 的帖子

Yes , correct




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