The elastic potential energy (Ep) is given by

Data:
Ep = ? (Joule)
k = 20 N/m
x (displacement) = 0.20 m
Solving:




Answer:

Explanation:
From the question we are told that:
Far point is 
Near point is 
Therefore
Focal Length

Generally the equation for the Lens is mathematically given by



B) 20-40 percent
I hope this helps
Answer:
C. Quadruple the intensity
Explanation:
The intensity of the sound is proportional to square of amplitude of the sound.
I ∝ A²

When the given sound is twice loud as the initial value, then the new amplitude is twice the former.
A₂ = 2A₁

Thus, to make a given sound seem twice as loud, the musician should Quadruple the intensity