# Franck hertz experiment problem

• cooper607
In summary, the problem is asking for the potential difference needed to accelerate electrons to the point where they can emit the first line of the Balmer series, corresponding to a transition from n = 3 to n = 2. The wavelength and energy calculations are not relevant to finding the potential difference.
cooper607

## Homework Statement

a beam of electrons bombards a sample of hydrogen. through what potential difference must the electrons have been accelerated if the first line of balmer series is to be emitted

## Homework Equations

1/l=R(1/2^2-1/3^2)

E=hc/l

v=E/Q

## The Attempt at a Solution

i first tried to find the wavelngth corresponding to first balmer series where i put ni=2 &nf=3.. first let me know if this interpretation is correct

then i found the wavelength l=6.563* E-7 m

according to E=3.03*E-19J

and finally V=E/Q=1.89 V

but the result has to be 12.1 V

please let me know where's the problem

regrds

The first line of the Balmer series is emitted when the atom goes from n = 3 to n = 2. You found the wavelength and energy of that transition, but that's not what they asked for.

Hint: Before it can drop to a lower energy level it first must reach the higher level.

## 1. What is the Franck-Hertz Experiment?

The Franck-Hertz Experiment is a physics experiment that was first conducted in 1914 by James Franck and Gustav Hertz. It was designed to demonstrate the quantized nature of energy in atoms and to confirm the existence of discrete energy levels in atoms.

## 2. What is the purpose of the Franck-Hertz Experiment?

The purpose of the Franck-Hertz Experiment is to demonstrate the quantized nature of energy in atoms and to confirm the existence of discrete energy levels in atoms. This experiment also provides evidence for the Bohr model of the atom, which states that electrons exist in discrete energy levels around the nucleus.

## 3. What is the setup of the Franck-Hertz Experiment?

The Franck-Hertz Experiment involves a vacuum tube filled with gas, an electron gun, an anode, a cathode, and a collector electrode. The gas atoms are excited by the electrons emitted from the electron gun and their energy is measured by the collector electrode.

## 4. What is the main problem encountered in the Franck-Hertz Experiment?

The main problem encountered in the Franck-Hertz Experiment is the presence of secondary electrons. These electrons are emitted from the anode and can interfere with the measurement of the energy levels of the gas atoms. This problem can be minimized by using a collector electrode with a higher potential than the anode.

## 5. How is the data collected and analyzed in the Franck-Hertz Experiment?

The data in the Franck-Hertz Experiment is collected by measuring the current between the anode and the collector electrode at different voltages. The current will decrease in steps as the voltage increases, indicating the energy levels of the gas atoms. The data is then analyzed to determine the energy difference between the discrete levels and to confirm the quantized nature of energy in atoms.

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