Electromagnetic spectrum — practice question

A beam of visible light travels in a vacuum. What might its frequency be?

• A$5.0 \times 10^5\,\text{Hz}$
• B$5.0 \times 10^8\,\text{Hz}$
• C$5.0 \times 10^{11}\,\text{Hz}$
• D$5.0 \times 10^{14}\,\text{Hz}$