The sun’s surface vibrates from internal pressure waves reflecting off of the photosphere and passing through the solar interior. since these waves penetrate deep inside the sun, an analysis of the vibrations these waves cause at the surface can reveal unique information about the solar interior. the science of studying the vibrations on the surface of the sun is known as helioseismology. if you were a helioseismologist, which of the following observational methods could you use to obtain information about the solar interior?

c because the news are a source of information of things that happen on the daily and shows evidence about that particular topic

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