[AL][20分]光電效應

恩樂

2009-11-30 6:34 am

A light bean of intensity 400Wm^-2 and frequency 10^15Hz shines on a photocell of surface area 0.005m^2. 100 electrons are ejected from the surface per second

(1) Estimate the probability of electron emission per incident photon
(2) If the frequency of the light is increased, what happens to the probability ontained in (1)

回答 (1)

Prof. Physics

2009-11-30 5:54 pm

✔ 最佳答案

Power of the light beam in the surface area, P

= 400 X 0.005

= 2 W

So, in one second, there are an energy of 2 J passing through this region.

By E = nhf

2 = n(6.63 X 10^-34)(10^15)

No. of photons emitted, n = 3.02 X 10^18

(h is Planck constant)

As the photoelectron emission is one to one

So, the required probability

= 100 / (3.02 X 10^18)

= 3.315 X 10^-17

2. For the light frequency is increased, then by E = nhf, the number of photons emitted will be less.

And so, the required probability will be higher than that in (1).

參考: Physics king

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