Intensity of Light & Frequency

2009-02-22 7:26 am

If the intensity is fixed but the frequency is increased, the energy E of each photon is increased and the maximum KE of the electrons increases. However the number of photon is decreased such that the intensity remains unchanged.
Highlight左的地方就係我唔明的地方
Intensity唔變,唔應該係 the number of photon都唔變ge咩
點解係decrease...

the number of photoelectrons is directly proportional to intensity, right?

回答 (1)

天同

2009-02-22 8:41 am

✔ 最佳答案

Intensity of light is the amount of energy passing a unit area in a unit time.
But energy of a beam of light (photons)= N.h.f
where N is the number of photons, h is Planck's constant and f is the frequency of light (photon).
If there are n photons passing a unit area in a unit time (n = N/t, t is the time duration), the intensity of light, I = n.h.f
If n decreases, the intensity I could remain unchanged through an increase of light frquency.
From the above equation, it can be deduced that for a fixed frequency of photons, intensity is proportional to the number of photons.

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