An single electron bashes into an atom in a
discharge lamp
10 V
If atom fixed at this point in tube,
10eV
6 eV
3 eV
2 eV
+

If atom fixed at this point in tube,
list all the possible photon energies (colors) that you might see?
A. 1eV, 2eV, 3eV, 4eV, 7eV, 8eV
B. 4eV, 7eV, 8eV
C. 1eV, 3eV, 4eV
D. 4eV
E. Impossible to tell.
An single electron bashes into an atom in a
discharge lamp
10 V
If atom fixed at this point in tube,
10eV
6 eV
3 eV
2 eV
D
d
+

list all the possible photon energies (colors) that you might see?
A. 1eV, 2eV, 3eV, 4eV, 7eV, 8eV
B. 4eV, 7eV, 8eV
C. 1eV, 3eV, 4eV
D. 4eV
E. Impossible to tell.
Answer is D.
Electron only gains about 5eV!
Electron energy = q
∆
V = e(Ed),
where E is the electric field = (battery V)/(total distance D),
and d is the distance it goes before a collision.
Remember the ‘Electron Volt’ (eV)?
Define
new energy unit: The
electronvolt
(eV)
1eV = kinetic energy gained/lost by an electron when
accelerated/decelerated by traversing an
area with 1 Volt potential difference (such as in
a plate capacitor)
E
F
0V
1V
path
+
+
+
+
1eV
≈
1.6 ·10
19
J
Some handy relations:
1 Ampere = 1 Coulomb / Second
1 Watt = 1 Ampere · 1 Volt = 1 C/s · 1 V
Current flowing through a wire: