Which of these colours in the visible spectrum has the longest wavelength?

Analysis

The question asks you to identify which color of visible light possesses the longest wavelength. This is a fundamental concept in optics and wave motion, often tested in JAMB Physics regarding the electromagnetic spectrum.

Concept Explanation

Visible light is a small portion of the electromagnetic spectrum that the human eye can perceive. It consists of a range of colors, which can be remembered using the acronym ROYGBIV:

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

In the electromagnetic spectrum, there is an inverse relationship between frequency and wavelength. As you move from Red to Violet:

1. Wavelength decreases: Red has the longest wavelength, and Violet has the shortest.
2. Frequency increases: Red has the lowest frequency, and Violet has the highest.
3. Energy increases: Red has the lowest energy, and Violet has the highest energy.

Step-by-Step Solution

1. List the options: Red, Blue, Yellow, Violet.
2. Recall the spectrum order: Based on the ROYGBIV sequence, Red is at one end (longest wavelength) and Violet is at the other (shortest wavelength).
3. Compare the wavelengths: • Red: ~700 nm (longest) • Yellow: ~570–590 nm • Blue: ~450–495 nm • Violet: ~380–450 nm (shortest)
4. Conclusion: Comparing these values, Red clearly occupies the position of the longest wavelength in the visible spectrum.

Exam Tip

To remember this easily, think of a Rainbow. The Red color is always on the outer edge (the largest arc), which represents the "longest" path or wavelength, while Violet is on the inner edge (the smallest arc), representing the "shortest" wavelength.