Which statement about electromagnetic waves is true?
a. electromagnetic waves require a medium to travel.
b. electromagnetic waves don't require a medium to travel.
c. the particles of the medium through which electromagnetic waves travel vibrate perpendicularly to the direction of the wave.
d. the particles of the medium through which electromagnetic waves travel vibrate parallel to the direction of the wave.

Electromagnetic waves don't require a medium to travel.

B.Electromagnetic waves don't require a medium to travel.

Explanation:  

Electromagnetic waves can travel both in space as well as medium. These are transverse waves i.e. when they travel in medium, the medium particles vibrate perpendicular to the direction of motion of wave.

A electromagnetic wave is composed of electric and magnetic fields perpendicular to each other. These fields generate each other and that is the way an electromagnetic wave carries energy forward. An electromagnetic wave travels at the speed of light in space and slows down in medium. So, the correct answer is that an electromagnetic wave does not require a medium to travel. It can travel in space.

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c) both a and b.

the temperature in kelvin of 2.0 dm3 of an ideal gas is doubled and its pressure is increased by a factor of four. what is the final volume of the gas