What is blue in physics?

In physics, blue refers to light within a specific range of wavelengths in the visible spectrum.

Understanding Blue Light

Wavelength Range

• Blue light occupies the 450–495 nanometres range in the visible spectrum.
  • This range is after violet and represents the shortest wavelengths that humans can perceive with their eyes, as mentioned in a recent update on 26-Sept-2024.

Position in the Visible Spectrum

• The visible light spectrum encompasses the range of electromagnetic radiation that is visible to the human eye.
• Within this spectrum, blue light is positioned between violet, which has shorter wavelengths, and green, which has longer wavelengths.
• This specific positioning of blue light contributes to its unique visual characteristics.

How We See Blue

• Our eyes contain special cells called cones which respond to different wavelengths of light.
• The cones responsible for blue light are activated when light within the 450-495nm range enters the eye.
• This activation is interpreted by our brains, resulting in the perception of the color blue.

Practical Implications

• Technology: Blue light is used in screens, such as on phones and computers. The prevalence of these devices has brought attention to the potential effects of blue light on sleep cycles.
• Atmosphere: The blue appearance of the sky on a clear day is due to the scattering of shorter wavelengths of light (specifically blue) by air molecules. This is known as Rayleigh scattering.

Example

• If you were to pass white light through a prism, you would see a spectrum of colors from red to violet. The band between violet and green would be the blue light.