When exposed to a radioactive source which emits 1.2-mev gamma-rays, a particular material is found to have a half-value thickness x of 10 cm how thick would a shield made of this material need to be in order to block 75% of the radiation? a. 5 cm b. 20 cm c. 15 cm d. 25 cm e. 10 cm

E

Explanation:

It is given that Energy of gamma ray is E=1.2 Mev

Shielding effect can be measured by measuring the fraction of gamma rays blocked by shield. If certain thickness will able to block half the radiation then to block 75% radiation we need to add same amount of thickness in order to block the remaining radiation.

i.e. fraction is blocked by 10 cm thickness

then remaining radiation is

another 10 cm thickness will block the remaining half radiation i.e.

so total 75 % radiation will be blocked

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