c) Assume that in the experimental setup for this photoelectriceffect experiment

Question

c) Assume that in the experimental setup for this photoelectriceffect experiment, the two electrodes (emitting electrode and collecting electrode) areparallel to each
other and separated by 0.20m. Ignore edge effects and find:

(i) The magnitude of the electric field between the electrodes whena potential difference of 1.2V is applied to the electrodes.

The answer is 6 v/m

(ii)The magnitude of the acceleration of an electron between the two plates. (Hint: you need to use F=ma and the electric field you found in part (i) above.)

Explanation / Answer

( i ) The magnitude of electric field ( E ) between the electrodes can be obtained as

E = potential difference applied to the electrodes / Spcing between the electroded

E = V / d

V = 1.2V , d = 0.20m

E = 1.2 / 0.20 = 6V/m

( ii ) The electric force due to the electric field between the plates give an acceleration to the electron.

Thus electric force acting on the electron is equal to its force of motion.

Thus F = Fe

     ma = qE

where m is mass of electron,q is charge of electron,a is it's acceleration

a = qE / m

q = 1.6 * 10-19 C , m = 9.1 * 10-31 kg

a = (1.6 * 10-19 * 6 ) / ( 9.1 * 10-31 ) = 1.055 * 1012 m/s2

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