Question

electromagnetic waves vary in their frequencies and wavelengths. but in a given type of matter, or medium, all electromagnetic waves travel at the same constant speed - the speed of light. in a vacuum, the speed of light is $2.998\times10^{8}$ meters per second.
the table shows the speed of electromagnetic waves in different types of media.

select the true statements.
electromagnetic waves speed up when they pass from diamond into air.
a radio wave travels slower than an x - ray in a vacuum.
the speed of light in air is constant.
a microwave travels faster through glass than through water.

Explanation:

Step1: Analyze the first statement

Compare the speed of light in diamond ($1.239\times10^{8}$ m/s) and air ($2.997\times10^{8}$ m/s). Since $1.239\times10^{8}<2.997\times10^{8}$, electromagnetic waves speed up when passing from diamond to air.

Step2: Analyze the second statement

In a vacuum, all electromagnetic waves (including radio waves and X - rays) travel at the same speed ($2.998\times10^{8}$ m/s). So, a radio wave does not travel slower than an X - ray in a vacuum.

Step3: Analyze the third statement

In a given medium (here air), all electromagnetic waves travel at the same constant speed. So, the speed of light in air is constant.

Step4: Analyze the fourth statement

Compare the speed of light in glass ($1.999\times10^{8}$ m/s) and water ($2.250\times10^{8}$ m/s). Since $1.999\times10^{8}<2.250\times10^{8}$, a microwave does not travel faster through glass than through water.

Answer:

• Electromagnetic waves speed up when they pass from diamond into air.
• The speed of light in air is constant.