Question

In Davisson-German experiment, observed value of de-Broglie’s wavelength is 0.165$nm$ whereas theoretical value is 0.166$nm$. Choose the correct reason for lower experimental value.

• A. Error in observation of angle at which maxima of intensity of diffracted electron occurs.
• B. Temperature of nickel crystal is more than the ambient temperature
• C. Electron speed inside the crystal is more than $\sqrt{\left(\frac{2qV}{m}\right)}$ and no account is made to calculate this increase of speed.
• D. Electron behave like waves in this experiment.

Answer 1

The correct option is C

Electron speed inside the crystal is more than $\sqrt{\left(\frac{2qV}{m}\right)}$ and no account is made to calculate this increase of speed.

When an incident electron enters the metal surface, its kinetic energy increases by an amount equals to work function of metal and hence, its speed increases. No account of this increase in speed is made.