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

1. increasing the filament current

2. decreasing the filament current

3. decreasing the potential difference between the anode and filament

4. increasing the potential difference  between the anode and filament

Which among the following verified the wave nature of electrons experimentally?

1. De-Broglie 

2. Hertz

3. Einstein 

4. Davisson and Germer 

Consider the figure given below. Suppose the voltage applied to A is increased. The diffracted beam will have the maximum at a value of $\mathrm{\theta }$ that
                  
1. will be larger than the earlier value

2. will be the same as the earlier value

3. will be less than the earlier value 

4. will depend on the target