The speed of light in vacuum is around 300,000 kilometres per second (186,000 miles per second).
2. Variable Speed
The speed of light is less than in vacuum when traveling through different transparent substances containing ordinary matter. For example the speed of light in water is about 3/4 of that in vacuum.
Sunlight takes about 8 minutes and 17 seconds to travel the average distance from the surface of the Sun to the Earth.
4. Visible Light
Visible light is electromagnetic radiation that is visible to human eye.
5. Straight Path
Light travels in straight lines – as long as it is not interacting with anything!
The change in direction of light waves when they hit an object with a very smooth and shiny surface, like a mirror, is called reflection. Reflection also occurs at the surface of transparent media, such as water or glass.
The change in direction of light due to a change in its transmission medium, like air to water, is called refraction.
Visible light, as all other forms of electromagnetic radiation, is emitted and absorbed in tiny “packets” called photons, and exhibits properties of both waves and particles (wave–particle duality). Like all elementary particles, photons are currently best explained by quantum mechanics.
9. Less Than a Millionth
The electromagnetic spectrum extends from below the low frequencies used for modern radio communication to gamma radiation at the short-wavelength. Visible light, constitutes less than a millionth of one percent of the electromagnetic spectrum.
10. Ultraviolet Light
Above the range of visible light, ultraviolet light becomes invisible to humans, however many animals (such as insects and shrimps) are able to detect ultraviolet. Although invisible to the human eye, most people are aware of the effect that ultraviolet radiation has on human body. Life on Earth outside of the deep oceans is possible only because the atmosphere, primarily the ozone layer, filters out the vast majority of this light.
11. Infrared Light
Infrared light is popularly known as “heat radiation”. Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared, and this radiation accounts for 49 percent of the heating of Earth. Some animals, such as snakes and vampire bats, are sensitive to various types of infrared, they sense infrared as radiant heat and not by vision.
Light waves with different wavelengths produce the different colours. Red light has the longest wavelength while violet light has the shortest wavelength.
13. Primary Colours
Primary colours are not a fundamental property of light but are related to the physiological response of the eye to light. The colours red, green, and blue fall within the sensitivity ranges of each of the human cone cells. Species with different receptor cell types would require different primaries.
The most common light sources are thermal, like sunlight or glowing solid particles in flames.
Sunlight entering the water may travel about 1,000 meters (3,280 feet) into the ocean under the right conditions, but there is rarely any significant light beyond 200 meters (656 feet).
The process used by plants and other organisms to convert light energy into chemical energy that can be later released to fuel the organisms’ activities is called photosynthesis.
A rainbow is the result of an optical and meteorological phenomenon that is caused by both reflection and refraction of light in water droplets in Earth’s atmosphere.
18. Space is Black
Space is black to our perception because light is only visible when it has an object of which to bounce off. Since light goes in a straight line it seems to be absorbed by the void and vacuum of space.
UV lights or black lights is a lamp which emits long wave ultraviolet light and not much visible light. This kind of lights are employed for decorative and artistic lighting effects, diagnostic and therapeutic uses in medicine, the detection of substances tagged with fluorescent dyes, rock-hunting, the detection of counterfeit money, the curing of plastic resins, attracting insects and are often used by forensic scientists to see details that are not seen by the naked eye.
Optics is the branch of physics which involves the study of light, including its interactions with matter and the construction of instruments that use or detect it.