Question

In the Davisson Germer experiment, the velocity of electrons emitted from the electron gun can be increased by

• A. increasing the potential difference between the anode and cathode.
• B. decreasing the potential difference between anode and cathode.
• C. increasing the filament current.
• D. decreasing the filament current.

Hint:

- $v \propto \sqrt{V}$ - Filament current $\rightarrow$ controls intensity, not speed

Answer 1

The Correct Option is A

Concept:
In Davisson-Germer experiment, electrons are accelerated by a potential difference $V$ between cathode and anode. Kinetic energy gained: \[ \frac{1}{2}mv^2 = eV \]

Step 1: Relate velocity and potential.
\[ v = \sqrt{\frac{2eV}{m}} \]

Step 2: Analyze dependence.

• If $V$ increases $\Rightarrow$ $v$ increases
• If $V$ decreases $\Rightarrow$ $v$ decreases

Step 3: Check other options.
Filament current only affects number of electrons (intensity), not their velocity.

Step 4: Conclusion.
\[ \text{Velocity increases with accelerating potential} \]