Green light wavelength range in visible spectrum

Steps:

• Recall visible light spans 400-700 nm; green occupies 495-570 nm.
• Convert options from meters to nm: multiply each by 10^9 (A: 490 nm, B: 660 nm, C: 550 nm, D: 860 nm).
• Compare values to green range: 495-570 nm.
• Identify match: only 550 nm fits green.

Why C is correct:

• 550 nm falls within the standard green light range of 495-570 nm, per the visible spectrum classification.

Why the others are wrong:

• A (490 nm): Falls in blue-violet range (450-495 nm).
• B (660 nm): Falls in red range (620-700 nm).
• D (860 nm): Exceeds visible spectrum, in near-infrared (>700 nm).

Final answer: C