What is true for all of the examples of electromagnetic waves? a) they all move at the same speed in a vacuum. b) they all have the same wavelength. c) they all have the same frequency. d) they all have the same energy.

A statement that is true for ALL of the examples of electromagnetic waves is that;

A) They all move at the same speed in a vacuum

The reason for qualifying 'in vacuum' is because EM waves of different frequencies often propagate at different speeds through material. Generally speaking, we say that light travels in waves, and all electromagnetic radiation travels at the same speed which is about 3.0 * 108 meters per second through a vacuum.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.