White light ( 7000 4000) is projected on a photoelectric tube whose contact energy is 2eV. Adjust the stop voltage so that there

White light (Å 7000 – Å 4000) is projected on a photoelectric tube whose contact energy is 2eV. Adjust the stop voltage so that there is no current at all. What will be the impact on one of the following three variables: 

1) The threshold frequency; 

2) Saturation current; 

3) The stopping voltage under each of the changes in the experimental conditions listed below:
A. Placing a green filter in the path of light (blocks all wavelengths except those corresponding to green).
B. Approximating the light source to the tube.
C. Replacing the metal with lower bond energy.