How do scientists determine motion of objects in the universe? ?

By Doppler effect

Explanation:

The spectrum of the objects in the universe such as stars and galaxies is taken and studied. The apparent change in the frequency/wavelength of the light suggests the motion of these objects.

If the apparent frequency is greater, the light would be blue -shifted which means it is moving towards Earth and if it is red shifted, it would be moving away from the earth. This is apparent change in observed frequency is known as Doppler's effect which studied to determine the motion of objects in the universe.

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

i think the answer is a and b

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