Answer:
Explanation:
Given
Diameter of Plates is D
distance between Plates is d
Energy Stored in the Plates is U
Suppose fixed Potential is V
Energy is given by

where C=capacitance

where A=area of Plates

Thus 
Keeping all other factors as same

For triple the Energy

divide 1 and 2 we get


Thus the diameter should be change to
times of original value
Answer:

Explanation:
As per given figure let say the tip of the shadow is at distance "x" from the base of the lamp
so here we have

so we have


now we have



Ok the answer for this question would be B. Hope this helps.
1. friction between water molecules
2. the wave spreads out onto a larger and larger area, so per unit area, the energy of the wave goes down