In Franck Hertz experiment, how can we determine the excitation energy E A and excitation voltage from the graph ?(show an example please) 300 ???? 200 100 0 0 5 10 15 Voltage V Solution Franck Hertz experiment demonstrates the fact that electrons obey quantum physics according to which they can only be in particular stationary levels. Electrons were accelerated toward a positive grid in a glass chamber filled with mercury vapor. After the grid there is a collector plate held at small negative voltage The values of accelerting voltage where the current is dropped gave a measure of energy necessary to force an electron to the excited state. This drop is attributed to inelastic collisions between the accelerated electrons and mercury atoms electrons. The measured gaps between the peaks corresponds to excitation energy. Example: For neon gas, when the accelerated electrons excite the electrons of Ne to higher states, these electrons come to lower states in a manner where they emit visible light. There are nearly ten excited levels between 18.3 eV to 19.5 eV, when they come back to lower states at nearly 16.6 eV, there energy difference corresponds to visible light region. .

1. In Franck Hertz experiment, how can we determine the excitation energy E A and
excitation voltage from the graph ?(show an example please)
300 ???? 200 100 0 0 5 10 15 Voltage V
Solution
Franck Hertz experiment demonstrates the fact that electrons obey quantum physics according to
which they can only be in particular stationary levels.
Electrons were accelerated toward a positive grid in a glass chamber filled with mercury vapor.
After the grid there is a collector plate held at small negative voltage
The values of accelerting voltage where the current is dropped gave a measure of energy
necessary to force an electron to the excited state. This drop is attributed to inelastic collisions
between the accelerated electrons and mercury atoms electrons.
The measured gaps between the peaks corresponds to excitation energy.
Example: For neon gas, when the accelerated electrons excite the electrons of Ne to higher
states, these electrons come to lower states in a manner where they emit visible light. There are
nearly ten excited levels between 18.3 eV to 19.5 eV, when they come back to lower states at
nearly 16.6 eV, there energy difference corresponds to visible light region.