Question

determine whether each statement is true or false. all electromagnetic waves travel through air at the same constant speed. all electromagnetic waves travel at the speed of light. the frequency and wavelength of an electromagnetic wave are directly proportional. only radio waves have the ability to cause fat and water molecules to vibrate.

Explanation:

• First statement: Electromagnetic waves in a vacuum (and approximately in air) travel at the same speed \(c = 3\times10^{8}\space m/s\).
• Second statement: The speed of electromagnetic waves in a vacuum is the speed of light \(c = 3\times10^{8}\space m/s\).
• Third statement: The relationship between frequency \(f\), wavelength \(\lambda\) and speed \(c\) of an electromagnetic wave is \(c = f\lambda\). So \(f=\frac{c}{\lambda}\), which means frequency and wavelength are inversely proportional.
• Fourth statement: Microwaves (not just radio waves) are used to cause fat and water molecules to vibrate (e.g., in microwave ovens).

Answer:

• All electromagnetic waves travel through air at the same constant speed: True.
• All electromagnetic waves travel at the speed of light: True.
• The frequency and wavelength of an electromagnetic wave are directly proportional: False.
• Only radio waves have the ability to cause fat and water molecules to vibrate: False.