Infrared Radiation Travels Through Vacuum and Gases

Steps:

• Identify infrared as electromagnetic radiation, similar to visible light and radio waves.
• Recall that electromagnetic waves propagate through vacuum without medium.
• Note that gases like air are transparent to infrared, allowing transmission.
• Confirm solids absorb or scatter infrared, limiting travel.

Why D is correct:

• Infrared is an electromagnetic wave that travels at speed of light in vacuum and gases, per Maxwell's equations.

Why the others are wrong:

• A: Incorrect; infrared travels freely in gases like air.
• B: Incorrect; it also travels through gases, not limited to vacuum.
• C: Identical to D, but question specifies D as correct option.

Final answer: D