(MIT) The Photoelectric Effect
(MIT) The Photoelectric Effect
(MIT) The Photoelectric Effect
1. PREPARATORY QUESTIONS that matter radiates its energy in quanta of energy hν.
He postulated that light delivers its energy to an absorber
1. If a certain metal with a work function of φ = in quanta with energy hν. Thus, if it takes an amount of
2.5 eV is illuminated by monochromatic light of energy φ to lift an electron out of the surface and away
wavelength 3500 Å, what is the maximum kinetic from its image charge, then the residual kinetic energy
energy of the electrons ejected in the photoelectric K of the ejected electron is
effect?
1.5
a little from the ideal case. The anode ring is made from
1
platinum-rhodium alloy (φP t = 5.7 eV). Typical pho-
0.5
toelectric currents are 100-1000 nA. It is important to
0
3000 3500 4000 4500 5000 5500 6000 note that the electronic work function ‘W’ is a material
constant which incorporates the different emission poten-
6
x 10 With 4360 Angstrom Band−pass Filter
3 tials of the cathode and anode. The former is a difficult
2.5 quantity to estimate as due to the manufacturing process
2 which makes the cathode surface not homogeneous. It
Photons
Determine the cutoff value of the retarding voltage for If it (Vr ) = aVr + b. (2)
each of the filters, and assess the random and systematic
errors of each determination. Plot the cutoff voltages for two cases: (a) the data as recorded by you and
against the center frequency of the filter bandpass. Sug- (b) after scaling the data and errors to I0 = 1 nA.
gestion: You can probably make more reliable determina-
Id: 005.photoelectric.tex,v 1.7 2002/09/25 14:04:39 sewell Exp sewell 4
APPENDIX B: UV SAFETY