Modern Physics CTs
CTMP-1 A Neon lamp emit a strong red line. Sodium emits a strong yellow line. What accounts for
this difference?
A) The electrons in the discharge tube hit the neon atoms with more speed than the electrons hit the
sodium atoms
B) The electrons in the discharge hit the neon atoms with less speed than the electrons hit the sodium
atoms
C) The energy spacing between the electronic energy levels in the neon atom are smaller than in the
sodium atom.
D) The energy spacing between the electronic energy levels in the neon atom is larger than in the
sodium atom.
Answer: Yellow light is shorter wavelength than red light. So yellow photons are higher energy (E =
hc/ and higher energy photons correspond to larger energy spacing between allowed energy levels.
The energy spacing between the electronic energy levels in the neon atom are smaller than in the sodium
atom.
CTMP-2 When an emission line (color) appears brighter, that means:
A) Multiple photons are emitted for each electron transition
B) More electron transitions are occurring each second
C) The electronic energy levels are farther apart and thus the line appears brighter
D) A and B
E) B and C
Answer: More electron transitions are occurring each second. Each transition causes only 1 photon, so
brighter lines means more photons, more transitions.
