Visibility of electromagnetic waves

Steps:

• Visible light ranges from 400 nm to 700 nm (4.0 × 10^{-7} m to 7.0 × 10^{-7} m).
• Convert wavelength: 5.0 × 10^{-7} m = 500 nm.
• 500 nm is green light, visible to humans.
• Statement A wrongly claims invisibility.

Why A is correct:

• Visible spectrum definition includes 500 nm as green light, detectable by human eyes.

Why the others are wrong:

• B: All EM waves travel at speed c = 3.0 × 10^8 m/s in vacuum (space), but can differ in media.
• C: EM waves are transverse, allowing polarization (e.g., by filters).
• D: EM waves propagate via oscillating E and B fields, not requiring atoms in free space.

Final answer: A