OMG It's Everywhere! What is Light?
- 18 hours ago
- 9 min read
I could only return to Earth after a long trip to Andromeda. As I was entering the atmosphere, the rays of the Sun caught my eyes so much that at that moment, I thought to myself, "Have I ever written an article about what light is?" and realized that while I've mentioned natural-artificial light sources, the speed of light, light years, etc., I didn't have a post about light itself. I got a little angry at myself for leaving what I should have done at the very beginning to the end, but oh well, let's say better late than never and continue our universe explorations with our rocket. Now, sir, what is light and why does this friend appear before us everywhere? Let’s get started!
Contents
What is Light?
Light is the electromagnetic radiation in the universe formed by small particles called photons. However, do not let this definition mislead you; light can behave as both a wave and a particle and must be so by its nature. It has no mass and is therefore considered the fastest matter in the universe we live in.
How is Light Formed?
Light is formed during the transitions of electrons in atoms between energy levels. When an electron moves from a high-energy level to a low-energy level, it emits the energy difference in the form of a light particle called a photon. This process is the fundamental mechanism of light formation at the atomic level.
Suppose an electron is excited to energy level E2 while at energy level E1 (E2 > E1). Afterwards, as the electron returns to the E1 level, energy in the amount of E2 - E1 is released. This energy difference is emitted as a photon. The energy of the emitted photon determines the photon's wavelength. Photons with higher energy have shorter wavelengths, while photons with lower energy have longer wavelengths. These waves can propagate even in a vacuum and do not require any medium.
How Does Light Move?
Light travels as electromagnetic waves, and this movement is characterized by various phenomena such as linear propagation, refraction, reflection, diffraction, interference, dispersion, and polarization. These properties occur because light possesses both wave and particle characteristics and can be observed in daily life.
Does Light Refract?
Yes, light can refract as it passes through different media. Light refraction is defined as the change in the speed of light, and therefore its change in direction, as it passes from one medium to another. Refraction occurs when light transitions between two media with different densities. As light passes from one medium to another, it shows changes in its angle of refraction and speed depending on its wavelength.
Through Which Substances Can Light Pass?
Light can generally pass through transparent or translucent substances. While these types of substances allow light to pass freely, in other substances, it is absorbed or reflected. Light exhibits different effects depending on the structure and properties of the substances it can pass through:
Transparent Substances: Transparent substances such as water, glass, and plastic are materials through which light can largely pass. However, the thickness, purity, and surface roughness of these substances can affect the transmission of light.
Translucent Substances: Some substances pass some of the light while absorbing or reflecting another part of it. For example, substances such as ice or frosted glass are translucent.
On the other hand, opaque substances like metal largely reflect or absorb light. Light cannot pass through these substances and generally turns into heat as a result of reflection or absorption.
Does Light Have a Speed?
Yes, light has a speed and this speed is constant in a vacuum. The speed of light is known to be approximately 299,792,458 meters/second or approximately 299,792 kilometers/second. This constant speed is considered a universal speed limit according to Einstein's theory of relativity. If you want to learn the details about the speed of light, here: Who can keep up? What is the speed of light, and why is it so fast?
How Do We Measure the Speed of Light?
There are various methods for measuring the speed of light:
Fizeau Method: In this method, light is reflected by a rotating mirror, and we calculate the speed of light by measuring the reflection angle that changes depending on the rotation speed.
Michelson-Morley Experiment: In this experiment, an interferometer is used to measure the speed of light. Whether light moves in different directions and the speed of this movement are measured.
Lasers: With modern technology, the speed of light can be measured very precisely using lasers and sensitive time-measuring devices. The speed of light can be calculated by sending laser beams to a distant location and back and measuring the duration.
Is It Possible to Reach Light Speed?
No, it is not possible to reach the speed of light. According to Einstein's theory of special relativity, the speed of light is a universal speed limit. No particle of matter or energy can reach or exceed the speed of light. This theory defines the fundamental principles regarding the motion of light and time and explains how time can change as the speed of an object increases.
The reasons why reaching the speed of light is practically impossible are as follows:
Increase in the mass of matter: As an object approaches the speed of light, its mass increases toward infinity. This makes its acceleration impossible.
Energy requirement: Infinite energy is needed to bring an object to the speed of light, which cannot be provided in practice.
For these reasons, no object or particle can reach the speed of light, and this speed limit is accepted as a fundamental part of universal physical laws.
Can Light Be Used as a Unit of Measurement?
Yes, light can be used as a unit of measurement under certain conditions. The propagation speed and properties of light around the Earth can be taken as a reference to measure other physical quantities such as time and distance. The speed of light (c) is the fastest moving entity in the universe, and its speed in space is approximately 299,792,458 meters/second (about 300,000 km/second). The speed of light is used as a fundamental constant in distance measurements.
A light-year represents the distance light travels in one year and is used to measure astronomical distances. Additionally, the speed of light can be taken as a reference in time measurements. GPS systems determine location by using the propagation time of light. With these properties, light is considered an important unit of measurement in both scientific and practical applications.
You can find your questions about the light-year in my other blog: What is a light year and how many kilometers is 1 light year?
Is There Light in Space?
Yes, there is light in space. Although space is a vast vacuum, light and other types of electromagnetic radiation in different regions of the electromagnetic spectrum can be found within it. Light propagates into space in the form of electromagnetic waves emitted from the sun, other stars, or other space phenomena.
What is Light Reflection?
Light reflection is the bouncing back of light from a surface when it strikes that surface. Reflection occurs depending on the angle of incidence (the angle at which light arrives) and the angle of reflection. This phenomenon can take different forms depending on optical and physical properties.
Types of Light Reflections
The types of light reflection are briefly as follows:
Specular Reflection (Angular Reflection): It is the phenomenon where the angle of incidence and the angle of reflection are equal when light hits a smooth surface. In this case, if light hits the surface perpendicularly, it reflects at the same angle. This type of reflection is seen on smooth surfaces like flat mirrors.
Diffuse Reflection: It is the phenomenon where light scatters in different directions when it hits a rough or matte surface. This type of reflection occurs due to the microstructures of the surface. For example, light hitting a matte paper or a wall surface reflects irregularly in all directions.
Mirror-like Reflection (Reflective Surfaces): It is seen in cases where the surface is extremely smooth and shiny. In this case, when light hits a smooth surface, the angle of reflection is the same as the angle of incidence, and the reflection can be extremely clear and focused. Such reflections can generally be observed on mirrors or metallic surfaces.
Translucent Reflection: It is the case where light partially reflects and partially passes through when it hits a surface. For example, materials like frosted glass or translucent plastics reflect some of the light while transmitting a portion of it.
Polarized Reflection: It is the case where the reflected light vibrates in a plane-polarized direction. This type of reflection can generally be observed on polarized lenses or certain crystals.
Total Internal Reflection: It is the phenomenon where light traveling within an optical medium reflects completely as a result of striking the boundary surface of the medium at an angle greater than a certain critical angle. This condition is used in optical fibers, prisms, and some underwater lights.
What is the Wavelength of Light?
The wavelength of light refers to the length of a light wave within the electromagnetic spectrum. Light travels as electromagnetic waves, and the wavelength is the distance from one peak of these waves to the next peak. Wavelength is generally represented by the symbol $\lambda$ (lambda).
Briefly, light wavelengths are as follows:
Radio Waves: The wavelength can vary between 1 mm and 1000 km.
Microwaves: The wavelength can vary between 1 mm and 1 m.
Infrared Rays: The wavelength can vary between 700 nm (0.7 µm) and 1 mm.
Visible Light Wavelength: These are the wavelengths that the human eye can perceive.
Red: 620 nm - 750 nm
Orange: 590 nm - 620 nm
Yellow: 570 nm - 590 nm
Green: 495 nm - 570 nm
Blue: 450 nm - 495 nm
Violet: 380 nm - 450 nm
Ultraviolet Rays: The wavelength is generally measured in nanometers.
UV-A: 315 nm - 400 nm
UV-B: 280 nm - 315 nm
UV-C: 100 nm - 280 nm
X-Rays: The wavelength is generally measured in angstroms, ranging from 0.01 - 10 nm.
Gamma Rays: The wavelength is generally measured in femtometers, ranging from 0.01 nm - 0.1 nm.
What Are the Types of Light?
Light types vary depending on the wavelength at which the light travels, and not all of them can be perceived by the human eye.
Radio Waves: Have the longest wavelengths and lowest frequencies. Used in communication, radio and television broadcasts, and radar systems.
Microwave Waves: Wavelengths range from centimeters to millimeters. It is used in microwave ovens for cooking and wireless communication (Wi-Fi, Bluetooth).
Infrared: Used in applications such as heat dissipation, night vision devices and remote controls.
Visible Light: Electromagnetic waves detectable by the human eye, ranging from 380 nm to 750 nm. Used for illumination with natural and artificial light sources, photography, and visual perception.
Ultraviolet: Wavelengths range from 100 nm to 400 nm. Dec. Sterilization is fluorescent lamps and rays that cause sunburn.
X-Rays: Their wavelength range is between 0.01 nm and 10 nm. They are used in applications such as medical imaging (X-rays), security scans, and crystallography.
Gamma Rays: Have the shortest wavelengths and highest frequencies. Used in nuclear energy, medical treatment (cancer radiotherapy), and astrophysical researchh.
What Are the Different Types of Light?
Işık çeşitleri, kaynağına, oluşum şekline ve özelliklerine göre farklı kategorilere ayrılabilir. İşte temel ışık çeşitleri:
Type of Light | Examples |
Natural Light | Sun Light Moon Light Star Light |
Artificial Light | Bulb Light LED Light Fluorescent Light Halogen Light |
Laser Light | He-Ne Laser YAG Laser CO2 Laser |
Biological Light | Bioluminescence (Fireflies) Fluorescent Proteins |
Cold Light | Chemical Light Bars |
Polarized Light | Sunglasses LCD Screens |
Coherent Light | Laser Light (High Consistency) |
Diffuse Light | Light in Cloudy Days |
Luminescence | Fluorescent Light Phosphorescent Light |
A special series for those who want to delve deeper into light types:
My Migraine Flared Up from White Light: What Are Artificial Light Sources?
Of course, a comparison between these two is also on our menu:
Units of Measurement for Light
In addition to all these, light can be measured, and various units of measurement are used for different types and properties of light. The primary units used to measure different aspects of light, such as intensity, brightness, and energy, are as follows:
Measurement | Details |
Lumen(lm) |
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Lux (lx) |
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Candela (cd) |
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Watt (W) |
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Kelvin (K) |
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Foot-candle (fc) |
|
The units of measurement for light energy are two. These are:
Joule (J): The unit of measurement for light energy and represents the amount of energy emitted or absorbed by a light source.
Electronvolt (eV): A unit of measurement for photon energy and is used to measure the energy level of light.
What Are the Effects of Light on Human Health?
Light can have various positive and negative effects on human health. Sunlight is important for bone health and the immune system by helping our skin produce vitamin D. Natural light regulates the body's biological clock and affects our sleep patterns; exposure to sunlight in the morning promotes better sleep. Adequate natural light can reduce the risk of mental disorders such as depression and seasonal affective disorder; sunlight improves mood by increasing serotonin levels.
Prolonged exposure to artificial light can cause eye fatigue and digital eye strain. Additionally, blue light may damage the retina and disrupt sleep patterns. Insufficient natural light exposure, on the other hand, may increase the risk of chronic diseases such as obesity, diabetes, and cardiovascular diseases. The negative effects on humans are particularly widespread in areas with high light pollution.
What is Light Pollution?
Light pollution is an environmental problem caused by the use of unnecessary or excessive artificial light. Light pollution disrupts the natural darkness of the night sky, creating various negative effects. The effects of light pollution on humans are briefly as follows:
Night Sky Pollution: Excessive streetlights, billboards, and other light sources increase the brightness of the night sky, making it difficult to see stars and other celestial objects.
Effects on Wildlife: Light pollution can disrupt the natural behaviors of nocturnal animals. For example, baby sea turtles may head towards land instead of the sea.
Energy Consumption: Unnecessary light use leads to energy waste, which negatively impacts environmental sustainability. Energy consumption increases the use of fossil fuels, contributing to air pollution and climate change.
Effects on Human Health: Excessive exposure to artificial light can disrupt sleep patterns and reduce melatonin production, leading to health problems. Additionally, light pollution may increase health risks for night workers or those on night shifts.
Solution Suggestions: To reduce light pollution, it is important to use energy-efficient and directed lighting, turn off unnecessary light sources, and develop conscious lighting policies.
If you're curious about all the details of light pollution, let us direct you this way: What is Light Pollution? (All the Effects You Didn't Know About!)
With that, we have come to the end of our "What is Light?" blog. Stand by for more!
