Question

In a photoelectric-effect experiment it is observed that no current flows unless the wavelength is less than 570 nm .

What is the stopping voltage required if light of wavelength 450 nm is used?

Express your answer using two significant figures.

stopping voltage = ? v

Answer 1

What is stopping voltage: The stopping voltage is the voltage that gives a potential energy change equal to the maximum. or This is the additional energy the electron has after ejection.

Stopping Voltage = photon energy - work function

eV*0 = h*f - W0

Work function is where the kinetic energy of the photoelectrons is zero.

KE = hf - W0 = 0

W0 = hc/lambda = 6.63*10^-34*3*10^8/(1.6*10^-19*570*10^-9) = 2.18 eV

eV0 = (hc/lambda) - W0

= 6.63*10^-34*3*10^8/(1.6*10^-19*450*10^-9) - 2.18 eV

= 2.76 - 2.18

Stopping Voltage = 0.58 eV Ans