Answer:
That is, mechanical waves cannot travel through a vacuum. This feature of mechanical waves is often demonstrated in a Physics class. A ringing bell is placed in a jar and air inside the jar is evacuated. Once air is removed from the jar, the sound of the ringing bell can no longer be heard.
Answer:
The diameter of wire should be 
m
Explanation:
Given:
Current density 
Current 
A
From the formula of current density,
Where 
area of cylindrical wire = 
m
For finding the diameter of wire,
m
Therefore, the diameter of wire should be m
Nuclear chosen would be the gamma because it’s the one choose to be radioactive more than others
B.Because you cant pull out whenever you want just because you have the right away. Hope this helps.
