Light sources: Definition, Types and Sample Questions

Light is an electromagnetic radiation. If it had not been for light, we would not have been able to see the world around us. The human eye can only see a certain range of frequency of this electromagnetic radiation (about 390-700 nm). Light is a type of energy that, like all energies, comes from some sources which are known as light sources, responsible for producing the energy. In this article, we will discuss the definition, types, and sample questions of light sources.

Keyterms: Light, Radiation, Human eye, Electromagnetic radiation, Energy, Ultraviolet rays, Brain, Light sources, Rainbow, Light striking, Water droplets

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Light

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Light is an electromagnetic radiation that comes from a variety of sources known as light sources. It is a form of energy that may travel at high speed as a wavelength. The rainbow we see in the sky is a common example of light striking water droplets to split colors with distinct wavelengths, causing human eyes to interpret those different wavelengths of colors like a rainbow.

• The particles of light can emit radiation with a wavelength of roughly 390–700 nm, which is visible to the naked eye.
• Except for infrared and ultraviolet rays, the human eye can see practically all forms of light. 
• The light recorded by our eyes is further processed by our brain, which converts the energy bandwidth into the color spectrum that our brain and eyes are sensitive to.
• Humans are also making artificial light in the modern world, which is the most appropriate source of electrical energy in the current world. 
• Electrical light includes things like neon lights, light bulbs, and fluorescent tubes. Artificial light can also be seen in the form of lasers.

Light Spectrum

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Types of Light sources

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Light sources are of multiple types and fall into various categories. They can be categorized as follows:

Natural Sources

Our universe has abundant light-emitting objects throughout it that release light naturally. The light from these natural sources reaches the surface of the earth in the following ways:

• The Sun is the primary source of light for our planet. As it undergoes the process of nuclear fusion, immense energy is produced at the center of the sun, which makes it seem like a gigantic ball of fire. This energy at the core of the sun is released in the form of heat or light. The sun's light is one of the most important contributing factors for the long-term viability of life on Earth.

• Stars emit light as well, but due to the vast distance between the stars and the Earth, only a small fraction of light emitted by the stars reaches us.
• The moon is also responsible for providing light, although it cannot do so on its own. The light we see from the moon comes from the sun, which it then reflects.
• Due to some chemical reactions within various organisms, some of them are also able to produce light. This phenomenon is known as bioluminescence. Some examples of the organisms that can emit light are glow-worm, jellyfish, fireflies, microorganisms, and some other deep-sea plants.

• Lightning and volcanic explosions are also some examples of natural events that emit light.

Artificial Sources

• Artificial light includes light produced by technological means that bear a resemblance to sunlight (natural light). For instance, bulbs and tube lights.
• Artificial lights were invented at the turn of the twentieth century and since then have been widely used. They can be seen all around our surroundings.
• People commonly use artificial light in a variety of settings, including their homes, businesses, and other public spaces. These are available in a wide range of shapes, sizes, colors, and even brightness levels.

The artificial light sources can further be categorized as:

Incandescent Sources

Some objects, when heated at high temperatures, emit both visible and infrared light. These light sources are known as incandescent sources.

• They are the most prevalent sources of light which include the sun, light bulbs, and fires.
• When atoms are heated, thermal vibrations are emitted in the form of electromagnetic radiation. Incandescent light sources contain these vibrations in the entire atom.
• Materials emit different amounts of energy depending on their temperature; for example, at low temperatures, photons emit radiation with an infrared wavelength.
• When a metal is heated, the atoms in the metal vibrate and generate photons, which emit radiations that are visible to the human eye by increasing the wavelength in the spectrum.
• The most prominent example of incandescent light is fire, which involves a chemical reaction that emits both gases and heat, leading the substance to achieve a high temperature and become incandescent (lighten up).
• Similarly, electric light bulbs generate heat when an electrical current runs through them, raising the cable's temperature and eventually giving rise to incandescent light.

Electric Bulbs as an incandescent light source

Luminescent Sources

Luminescent Sources produce light by accelerating charges inside them. One way of accelerating charges is by passing a current through the material.

• These sorts of sources differ from incandescent light sources in that they only involve electrons rather than the entire material vibrations, and they occur at normal or lower temperatures, making them different from incandescent light sources.
• In general, we may say that luminescence light occurs when electrons emit some of their energy in the form of electromagnetic radiation.
• When an electron's temperature decreases, the energy level also decreases, resulting in the production of a certain color of light.
• Neon lights, fluorescent lights, bioluminescence, fluorescence light, and other luminescent light sources are common examples.
• Fluorescence light is the most prevalent type of luminescent light source, which is further separated into two types: electroluminescent and photoluminescent, both of which can be found on computer displays and televisions. Bioluminescence, which includes animals such as fireflies, is the most prevalent type of luminescence.

Luminescent Souce of Light

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Things to Remember

• Light is an electromagnetic radiation that comes from a variety of sources known as light sources, which can be described as the sources through which light (a type of energy) is created.
• Light is an energy form. It is essential for our existence because, without it, we would have to survive in the dark. 
• We all know that the sun is the most natural source of light, but other sources of light include electric bulbs, candles, torches, kerosene lamps, and so on.
• There are mainly two types of light sources i.e. Natural Light Sources and Artificial Light Sources. The artificial sources are further categorized as Incandescent Sources and Luminescent Sources
• Except for infrared and ultraviolet rays, the human eye can see practically all forms of light. The light recorded by our eyes is further processed by our brain, which converts the energy bandwidth into the color spectrum that our brain and eyes are sensitive to.

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Previous Year Questions

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• For a transparent medium relative permeability and permittivity … [NEET 2019]
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• Reflection of the point … [KCET 2017]
• For a normal eye, the cornea of the eye provides a converging power … [NEET 2013]
• Focal length of a convex lens of refractive index … [NEET 1988]
• Find the value of the angle of emergence from the prism … [NEET 2021]
• Assume that light of wavelength 600nm is coming from a star … [NEET 2020]
• An object is placed at a distance of 40 cm … [NEET 2018]
• A and B are two parallel-sided transparent slabs of refractive indices … [WBJEE 2016]
• A ray of light passes through four transparent media with refractive indices … [JEE Advanced 2001]
• A transparent slab of thickness dd has a refractive index n(z) … [JEE Advanced 2016]
• The angle of minimum deviation for an incident light ray on an equilateral prism … [KCET 2009]
• In refraction, light waves are bent on passing from one medium … [KCET 2021]
• Two plane wavefronts of light, one incident on a thin convex lens … [KEAM]
• For a crystal, the angle of diffraction … [BITSAT 2008]