Which of the following is a characteristic of electromagnetic waves?
they are all invisible.
o they have a dual wave-particle nature.
they can only travel without a medium.
they are slower than sound waves.

They have a dual wave-particle nature.

Explanation:

Electromagnetic waves consist of periodic oscillations of electric and magnetic field in a plane perpendicular to the direction of motion of the wave (in fact, they are also classified as transverse waves).

Electromagnetic waves have a wave nature, however they also have particle nature - in fact, it has been proved in some experiment (e.g. photoelectric effect) that in some conditions they act as packets of particles - called photons. Therefore, the option

They have a dual wave-particle nature.

is correct.

Other options are wrong because:

They are all invisible.  --> False because visible light (which is part of the electromagnetic spectrum, so they are electromagnetic waves) is visible

They can only travel without a medium.  --> False because they can also travel in a vacuum

They are slower than sound waves. --> False because they travel much faster (they travel at the speed of light in a vacuum, , while sound travels at 343 m/s in air, for instance)

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.