Question

Which of the following is a true statement?

a. Electromagnetic waves consist of only changing electric fields.
b. Electromagnetic waves are longitudinal waves.
c. Electromagnetic waves do not always need a medium to travel.
d. Electromagnetic waves can vary in speed, wavelength and frequency.

Answer 1

c. Electromagnetic waves do not always need a medium to travel.

Since they are transverse waves they do not need a material medium.

Answer 2

c. Electromagnetic waves do not always need a medium to travel.

Step-by-step explanation:

As the name suggests Electromagnetic waves consist of Electric and Magnetic fields.

Electromagnetic waves are transverse waves.

In a given medium Electromagnetic waves cannot vary in speed. However their wavelength and frequency can vary.

When an Electromagnetic wave travels through a medium It does not displace the medium. So, electromagnetic waves do not need a medium to travel.