Leon, a young chemist, assembled a photoelectric experiment as they learned in Chem 20A class. With a cobalt (Co, Φ = 5.00 eV) photocathode, they initially used a blue laser with wavelength λ=450 nm. Interestingly, Leon observed no photoelectron ejection and cannot understand why. 1 ?? = 1.602 × 10−19 � a) Briefly explain why photoelectron ejection is not observed. b) Can you suggest a maximum wavelength required to obtain photoelectron ejection from the cobalt photocathode? c) Leon switched to a UV laser with wavelength λ=200 nm. What is the maximum kinetic energy of the ejected photoelectrons?
Leon, a young chemist, assembled a photoelectric experiment as they
learned in Chem 20A class. With a cobalt (Co, Φ = 5.00 eV) photocathode, they
initially used a blue laser with wavelength λ=450 nm. Interestingly, Leon
observed no photoelectron ejection and cannot understand why.
1 ?? = 1.602 × 10−19 �
a) Briefly explain why photoelectron ejection is not observed.
b) Can you suggest a maximum wavelength required to obtain
photoelectron ejection from the cobalt photocathode?
c) Leon switched to a UV laser with wavelength λ=200 nm. What is the
maximum kinetic energy of the ejected photoelectrons?
d) ) Calculate the De Broglie wavelength of the ejected photoelectrons in
part c). Assume ejected photoelectrons all have maximum kinetic energy
e) Leon then used the ejected photoelectrons in electron diffraction
spectroscopy with a silicon crystal. They obtained a good diffraction pattern.
What is the approximate crystal spacing in this piece of silicon crystal?
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