Which of the following is not a characteristic of electromagnetic waves?
a. they can travel through a vacuum.
b. they can travel at various speeds through any one material.
c. they can be refracted.
d. they can be reflected.

Answer : The incorrect option is, (b) they can travel at various speeds through any one material.

Explanation :

Electromagnetic waves : It is a type of energy which is produced by the oscillating magnetic and electric filed disturbance. Or we can say that it is produced by the movement of electric charged particles through the vacuum or matter.

It is a wave where the two vectors are vibrating mutually perpendicular to each other and in direction of the wave. The two vectors are electric field and magnetic field.

The gamma-rays, x-rays, ultraviolet-rays, infrared-rays, microwaves and radio-waves are the electromagnetic waves.

The characteristic of electromagnetic waves are :

Hence, the incorrect option is, (b) they can travel at various speeds through any one material.

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.