The Nature of Light

The human eye uses three types of cone cells to perceive color, which are sensitive to red, green, and blue light. Yellow is a secondary color perceived by the brain when red and green cones are stimulated simultaneously.

Earth's atmosphere is opaque to high-energy, high-frequency radiation like X-rays and gamma rays, which are absorbed by the upper atmosphere. This protects life on the surface from harmful ionizing radiation.

The atmosphere acts as a filter, allowing only certain wavelengths (like visible light and radio waves) to reach the surface while absorbing others like X-rays and gamma rays.

Ultraviolet light has a higher frequency and shorter wavelength than visible violet light. It is located just beyond the violet end of the visible spectrum.

Infrared radiation has longer wavelengths than visible red light. It is emitted by objects based on their temperature, which is why it is often associated with heat.

Several animals have evolved to detect light outside the human visible spectrum. For example, some snakes can detect infrared radiation to hunt, and many insects can see ultraviolet light to locate flowers.

The visible light spectrum is bounded by ultraviolet light on the high-frequency side and infrared light on the low-frequency side. These two are the closest to the visible range.

The Sun is a massive source of energy that emits radiation across the entire electromagnetic spectrum, from high-energy gamma rays to low-energy radio waves.

Visible light is the specific range of electromagnetic radiation that the human eye is capable of detecting, typically ranging from about 380 to 750 nanometers.

The visible spectrum is a very small sliver of the entire electromagnetic spectrum. Humans cannot see most types of radiation, such as radio waves, microwaves, or X-rays.

The electromagnetic spectrum is the collective term for all possible frequencies of electromagnetic radiation, ranging from radio waves to gamma rays.

White light is composed of all the colors of the visible spectrum combined. When these wavelengths are present in equal proportions, the human eye perceives white.

Within the visible light spectrum, violet light has the shortest wavelength and highest frequency. Red light has the longest wavelength.

Red light occupies the end of the visible spectrum with the longest wavelengths. Violet light occupies the end with the shortest wavelengths.

The human eye and brain interpret different wavelengths of visible light as different colors. This is the basis of human color vision.

Radiation is the transfer of energy through space by electromagnetic waves. It does not require a medium to travel.

In an electromagnetic wave, the oscillating electric field and the oscillating magnetic field are perpendicular to each other, and both are perpendicular to the direction of wave propagation.

Electromagnetic waves are generated by the acceleration or vibration of electrically charged particles. This motion creates the oscillating electric and magnetic fields.

By definition, an electromagnetic wave consists of time-varying electric and magnetic fields that are coupled together.