Asample of a material has 200 radioactive particles in it today. your great-grandmother measured 400 radioactive particles in it 100 years ago. 100 years from today, how many radioactive particles will the sample have?

100 Radioactive particles

Explanation:

If your great-grandmother measured 400 radioactive particles 100 years ago and today it has 200 radioactive particles, we observe that the half-life of this particles is 100 year.

That means that each 100 years the number of radioactive particles drop to half of it's original number.

400 radioactive particles--100 year--200 radioactive particles --100 years-- 100 radioactive particles

ok

explanation:

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia