Answer:
Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.
More mass is the correct answer.
Visible light has a wavelength of 400-700nm, which means light microscopes cannot see anything smaller than this. Atoms are much smaller than this, so they are not visible to light microscopes.
Answer:

Explanation:
It is given that,
Charge on helium nucleus is 2e and its mass is 
Speed of nucleus at A is 
Potential at point A, 
Potential at point B, 
We need to find the speed at point B on the circle. It is based on the concept of conservation of energy such that :
increase in kinetic energy = increase in potential×charge

So, the speed at point B is
.