Which colour has the longest wavelength in visible light?

**The reasoning** In visible light, wavelength determines colour. The electromagnetic spectrum follows a pattern: **wavelength increases as you move from violet to red**. Think of it like this — violet light has wavelengths around 380-450 nm (nanometers), while red sits at 620-750 nm. Red has nearly double the wavelength of violet! Here's the order from shortest to longest wavelength: **Violet → Blue → Green → Yellow → Orange → Red** Remember the acronym **ROYGBIV** (rainbow colours), but flip it backwards for wavelength: **Red has the longest, Violet has the shortest**. **Why the wrong options tempt you** - **Violet** is the most energetic visible light, so students confuse "high energy" with "long wavelength" — but they're actually *inversely* related. - **Green and Yellow** sit in the middle of the spectrum, so they feel like safe, middle-ground answers when you're unsure. **Quick takeaway** In visible light, **red light travels in the longest waves, violet in the shortest** — remember: energy and wavelength move in opposite directions.