What is the Difference Between Red Light and Infrared

The key difference between red light and infrared is that red light is visible, whereas infrared light is invisible.

Red light is the radiation having the longest wavelength among the other wavelengths in the visible spectrum. Infrared radiation, on the other hand, is a type of electromagnetic radiation having a wavelength range of 700 nm – 1 nm.

CONTENTS

1. Overview and Key Difference
2. What is Red Light 
3. What is Infrared
4. Red Light vs Infrared in Tabular Form
5. Summary – Red Light vs  Infrared

What is Red Light?

Red light is the radiation having the longest wavelength among the other wavelengths in the visible spectrum. In other words, red light shows the lowest frequency compared to other colored light radiations in the visible spectrum.

The visible spectrum can be described as the portion of the electromagnetic radiation that is visible to our eyes. This light has a range of wavelengths from 380 nm to 750 nm. The red color has a wavelength range of 630-700 nm. Frequency ranges between 400 to 480 THz. However, we cannot sharply define these bands because electromagnetic radiation is usually given as a continuous spectrum.

Typically, clean air scatters blue light more than red light. Therefore, the midday sky appears in blue color. Inside glass materials, the red color moves faster compared to violet. Therefore, red light beam is bent less than violet light. This is called the refraction of light, and different colored light beams show different refractions, creating a spectrum of colors. The red color is in one of the visible spectra, and the other end has a violet color.

What is Infrared?

Infrared radiation is a type of electromagnetic radiation having a wavelength range of 700 nm – 1 000 nm. Therefore, the wavelength range of this radiation is longer than that of visible light. This makes this radiation invisible to the human eye. Infrared radiation can be abbreviated as IR radiation. It begins from the red edge of the visible light. Thermal radiation emitted by an object such as the human body (near room temperature) is emitted in the form of IR radiation. Moreover, similar to all types of electromagnetic radiation, IR radiation carries a certain amount of energy, and this radiation can act as both wave and particle form. The normal frequency range for this radiation is 430 THz to 300 GHz.

Generally, IR radiation contains a spectrum of wavelengths. Thermal IR radiation also has a ma proportional to the object’s absolute temperature cure of the object from which the IR radiation is emitted. Some of the smaller sections of the IR radiation band include near-infrared, short wavelength-infrared, mid-wavelength-infrared, long wavelength-infrared, and far-infrared radiation. However, we can divide the band of infrared radiation in the electromagnetic spectrum into three major parts: IR-A, IR-B, and IR-C. The bands can also be known as near-IR, mid-IR, and far-IR.

In general, IR radiation is used as thermal radiation or heat radiation. The radiation coming from the sun accounts for 49% of IR wavelengths. This causes the heating of the Earth’s surface. Unlike the other methods of heat transfer, e.g. conduction and convection, thermal radiation can transfer heat through a vacuum. IR radiation that is emitted from human bodies is important in making night vision equipment.

What is the Difference Between Red Light and Infrared?

Electromagnetic radiation has different ranges of wavelengths that have different frequencies. Visible light and infrared are two such ranges. Infrared radiation is a type of electromagnetic radiation having a wavelength range of 700 nm – 1 nm, while red light is the radiation having the longest wavelength among the other wavelengths in the visible spectrum. The key difference between red light and infrared is that red light is visible whereas infrared light is invisible.

The below infographic presents the differences between red light and infrared in tabular form for side by side comparison.

Summary – Red Light vs Infrared

Red light is the radiation having the longest wavelength among the other wavelengths in the visible spectrum. Infrared radiation is a type of electromagnetic radiation having a wavelength range of 700 nm – 1 nm. The key difference between red light and infrared is that red light is visible, whereas infrared light is invisible.

Reference:

1. “Infrared Radiation.” Sensor Division Knowledge, Infratec.

Image Courtesy:

1. “Light dispersion of a mercury-vapor lamp with a flint glass prism IPNr°0125” By D-Kuru – Own work (CC BY-SA 3.0 at) via Commons Wikimedia
2. “Blue infrared light” By RockMancuso at the English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia