How fast would sound wave travel than the other if a signal was sent through air and water by a distress ship at sea 1 mile from a light house when temperature is 20 °c. p(sound in air at 0°c is 331 m/s and for every at in temperature of air the speed increases by 0.6 m/s. sound waves in under water travel 3 times faster than air.

3.13 s difference

Explanation:

Velocity of sound  in air at 20°C = 331 + .6 X 20 = 343 m s⁻¹

Velocity of sound in water at 20°C = 3 X 343 = 1029 m s⁻¹

Time taken by sound in air to cover 1 mile or 1609 m distance

=

= 4.69 s

Time taken by sound in water to cover 1 mile or 1609 m distance

=

1.56 s

difference = 3.13 s .

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