Why would companies want their sunscreen to absorb nearly all of the UV light?

Sunscreen is like a shield, you would want a better shield to protect you than a weak one so companies try to make their sunscreen better than the rest.

Explanation: UV light is very dangerous to the skin so it helps with sunburn,skin sensitivity,etc.

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.

a coal burning power plant