Ch25_1
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1) A photon has a wavelength of x10
-7
m
. What is its energy in
eV
(
sheet 4
) ? Indicate with a positive (negative) sign whether the photon energy increases (decreases) with increasing wavelength.
2) A "blackbody" (ideal emissivity - not essential here) emits an electromagnetic spectrum which has its maximum intensity at a wavelength of
nm
. What is the temperature of the backbody in
0
C
(
sheet 4'
) ? Indicate with a positive (negative) sign whether when heating up a piece of metal and observing the colors of the emitted light the blue (red) light appears first.
3) An electron traverses a stopping voltage of hundred
volts
before it comes to rest. What is its initial kinetic energy in
eV
(
sheet 7
) ? Indicate with a positive (negative) sign whether the electron travels toward the high (low) potential side.
4) The "workfunction" of a metal emitting electrons via the photoelectric effect is
eV
. What is the threshold frequency i.e. the frequency below which no photoelectrons are emitted (
sheet 9
) ? Indicate with a positive (negative) sign whether for a certain metal an incident photon in the ultraviolet (infrared) is more likely to release an energetic electron.
5) A photon has a wavelength of
nm
. What is the photon momentum in
eV/c
(
sheet 14
). Indicate with a positive (negative) sign whether the momentum unit quoted is (not) an SI unit.
6) A
KeV
photon scatters off an electron (Compton Effect) and has a wavelength of
nm
after the collision. What is the kinetic energy of the recoil electron in
KeV
(
sheet 15-18
) ? Indicate with a positive (negative) sign whether the electron kinetic energy is of the same order of magnitude as (considerably smaller than) the electron rest energy.
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