Answer:
Explanation:
The plates A and B are charged by opposite charges but which plate is positively charged and which is negatively charged is not clear.
Now a proton which is positively charged is moving from plate A to B . If it is attracted by plate B then its kinetic energy will be increased and potential energy will be decreased due to conservation of energy . In that case B will be negatively charged .
But in the given case it is stated that
potential energy of the proton increases . That means its kinetic energy decreases . In other words its speed decreases . It points to the fact that plate B is also positively charged.
So proton will be repelled and its speed will be decreased.