Which color of light has the longest wavelength?

Answer: The correct answer is D) Red. In the visible light spectrum, Red has the longest wavelength (about 620 – 750 nanometers), while Violet has the shortest (around 380 – 450 nanometers). The visible colors follow the order VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, Red from shortest to longest wavelength. Since frequency and wavelength are inversely related, red light has the lowest frequency and violet light has the highest. That’s why Red light has the longest wavelength and is the correct answer.

Complete Answer:

To find which color of light has the longest wavelength, we should understand the wavelength and frequency values of different visible colors. The visible spectrum for human eyes ranges from 380 to 750 nanometers (nm) in wavelength.

Wavelength Order (Shortest to Longest):

The correct color order based on wavelength is called VIBGYOR:

Violet < Indigo < Blue < Green < Yellow < Orange < Red

• Violet: 380–450 nm
• Indigo: 450–460 nm
• Blue: 460–495 nm
• Green: 495–570 nm
• Yellow: 570–590 nm
• Orange: 590–620 nm
• Red: 620–750 nm

So, as you move from violet to red, the wavelength increases, and the frequency decreases (since they are inversely related).

Now let’s understand why other options are incorrect:

A) Violet – Violet has the shortest wavelength (~380–450 nm) and highest frequency. It is at the beginning of the visible spectrum.

B) Green – Green lies in the middle of the spectrum (~495–570 nm). Its wavelength is more than violet and blue but less than orange or red.

C) Blue – Blue (~460–495 nm) has shorter wavelength than green and much shorter than red.

D) Red – Red light has the longest wavelength (~620–750 nm) and lowest frequency. It travels the farthest and bends the least. That’s why red is used in warning signals and traffic lights—it is visible from far away.

Important points:

• Wavelength is measured in nanometers (nm), and frequency in Hertz (Hz).
• One wave’s wavelength is the distance between two peaks or troughs.
• Light with higher frequency has shorter wavelength, and vice versa.
• Visible Light Spectrum is just one small part of the electromagnetic spectrum, which also includes UV rays, infrared, X-rays, etc.

Thus, Red light has the longest wavelength among all visible colors, and that’s why D) Red is the correct choice.

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