what is light
For human beings, light is an indispensable element for us to experience the world. Because of light, we have a deeper understanding of the world. Light brings us more emotional feelings and enriches our spiritual world. If there is no light, we will not be able to perceive the light and shade, warmth, width, gathering and scattering, stillness, movement, speed, etc. of all things in the world.
In physics, the definition of light is electromagnetic radiation that can be perceived by the human eye.
Visible light has wavelengths in the 400-700 nanometer (nm) range, corresponding to frequencies of 750-420 terahertz, between the longer wavelengths of infrared and shorter wavelengths of ultraviolet, see Wikipedia Light.
Light affects human life and culture, and it produces photosynthesis with plants, making the human living environment full of vitality because of light.
In the great paintings, literature, film and television, and architectural works of human beings, we can always feel the metaphor and pursuit of light, which enriches the spiritual level of human beings.
Effects of light on human physiology
With light, the earth has a cycle of day and night, which forms a cycle every 24 hours. The creatures that live on the surface of the earth also follow the alternation of day and night on the earth and evolve to form their rhythms and laws of life. Talking about the physiological impact of light on the human body, the circadian rhythm is an unavoidable topic.
1、Human Circadian Rhythm
Circadian rhythm refers to the rhythm and regularity of life activities changing in a cycle of about 24 hours a day. Circadian rhythm is closely related to human activities and affects human physiological functions, learning and memory abilities, emotions, work efficiency, etc.
Around 6:00 in the morning, the large intestine of the body begins to detoxify, the body gradually wakes up, the blood pressure rises, the heartbeat speeds up, and the activities and work of the day gradually begin. Most of the work of human beings is completed during the day. To complete work tasks efficiently.
After 9 p.m., the immune system (lymph) starts to detoxify, and in the middle of the night, the body’s liver, gallbladder, and lungs start to detoxify. This period is the best time for human cell metabolism.
2、How do circadian rhythms affect health?
In October 2020, researchers from the University of Buenos Aires in Argentina and Virginia Tech published a research paper entitled: Circadian disruption promotes tumor-immune microenvironment remodeling favoring tumor cell proliferation in the journal Science Advances.
This study demonstrates that in mammals, long-term dysregulation of circadian rhythms can lead to the development of many diseases, such as cardiometabolic syndrome, obesity, and physical and mental health disorders. At the same time, studies have shown that circadian rhythm imbalance can also affect the expression of genes related to cell cycle, cell death, and DNA damage, thereby increasing the growth rate of tumors.
Although mice are used as the research object, they cannot be ignored by humans who are also mammals. It is often reported on various websites that people with circadian rhythm disorders suffer from diseases due for various reasons.
Circadian rhythm is closely related to our physical health. Many factors affect the imbalance of circadian rhythm. Below we share how to use light healthily to maintain a good circadian rhythm in the body.
3、How does light affect the body’s circadian rhythm?
According to related research, when light enters the eyes, the suprachiasmatic nucleus (SCN) converts this information into nerve signals and then controls functions such as body temperature and sleep. The SCN is like the body’s master clock, adjusting every cell in our body The circadian timing of the biological clock so that the biological clock and the cells of the body are synchronized with each other and with the external time of day. Among visible light, the human body is most sensitive to blue light.
So what is Blu-ray? In layman’s terms, it is the blue light seen by the naked eye, but not only blue light exists. When the light is white, there will still be blue light, that is, the spectral wavelength is in the range of 400-500 nm. light.
When our eyes are exposed to blue light, melanopsin in the eyes inhibits the production of melatonin, a hormone that controls sleepiness, and the brain controls every cell in the body, making the brain and body excited.
4、What is healthy light for human circadian rhythms?
Combined with the human body’s circadian rhythm table above, we can see that we need to stay focused and energetic during the day, that is, when the human body needs to focus on work, more blue-band light is healthy for the human body.
At night, the body needs to rest and relax, and it needs to secrete melatonin to promote sleep. At this time, we need to reduce exposure to blue light, exposure to soothing light that does not inhibit melatonin, and contain less blue when the body needs to rest Light in the wavelength band is healthy for the human body.
5、The effect of light color on the body
There is no doubt that blue light has the greatest impact on the circadian rhythm of the human body. Whether it is visibly red, yellow, green, blue, orange, blue, purple light, or invisible ultraviolet and infrared light, it has various effects on human body functions…
- Red light:
stimulate the sensory nervous system, stimulate the liver, and accelerate the detoxification of the skin.
- Yellow light:
activate muscles, stimulate the nerves of the motor system, stimulate the lymphatic system, stimulate the small intestine, and pancreas, and produce digestive juices such as bile, etc.
- Greenlight:
Stimulates the reconstruction of muscle tissue, and destroys microorganisms, bacteria, and pathogens.
- Blue light:
Promote sweating, relieve itching, relieve injured skin, mild sedative, cools down and reduces inflammation, and stimulates the pineal gland.
- Orange Light:
Soothes muscles, helps to vomit inappropriate substances in the stomach, relieves flatulence accumulated in the digestive system, builds bones, and promotes calcium application to correct soft bones and cartilage.
- Cyan light:
Stimulate and construct the parathyroid gland, inhibit the thyroid gland, control ulcers, reduce secretion and bleeding, relieve pain, relieve excitement and hyperactivity, and promote the production of macrophages to eliminate harmful microorganisms, bacteria, and pathogens.
- Purple light:
reduce pain sensitivity, help relax and fall asleep, lower body temperature and lower blood pressure, stabilize heart and lung blood pressure, and control fever and high blood pressure caused by malaria and relapsing fever.
- Ultraviolet rays:
Sterilize and disinfect, promote the synthesis of vitamin D in the human body, enhance the immune ability of the human body, and stimulate the hematopoietic function of the human body.
- Infrared rays:
improve human microcirculation, improve immunity and disease resistance, reduce inflammation, reduce swelling, activate blood circulation and relieve pain, etc.
The influence of light on human psychology
1、Psychological Effects of Light on Humans
Da Vinci once said that “the eyes are the windows of the soul”, which shows that the eyes are closely related to the psychological activities of the human body. Therefore, the brightness of light, the color of light, and the comfort of light to human eyes are important factors that affect human psychology.
2、Psychological Effects of Brightness
Bright light always gives people a positive, optimistic, and stable feeling. When we can clearly distinguish the surrounding environment, bright light will give us a sense of security. But when the led light becomes too bright, whether it is direct or reflected light, it will cause glare to the eyes. In addition to causing physical damage to the eyes, it will also make people feel restless and restless!
Dim light can sometimes give people a sense of tranquility and comfort, and sometimes it can also give people a feeling of fear and depression, causing nervous tension.
It can be seen that light affects the inner activities of the human body. To avoid giving people wrong psychological feelings and causing physical and mental health damage, appropriate space brightness is one of the factors for healthy light.
3、Psychological effects of color temperature
The emotional response caused by the color of light is spontaneous, usually, the perception of the color of light by the human eye, and the psychological impact may be positive or negative.
Usually, we divide the color temperature of light into three categories, namely: warm colors, neutral colors, and cool colors.
- Warm color light:
usually refers to light with a color temperature below 3300K, and the light of an incandescent lamp is often used as a representative of warm color light. The color temperature of around 2000K is similar to candlelight, with more red light components, which can give people a warm and intimate feeling.
- Neutral color light:
usually refers to light with a color temperature between 3300K and 5300K. Due to the fusion of some warm color light and cool color light, the light is softer than cold color light, making people feel happy, comfortable, and relaxed.
- Cool light:
Daylight close to noon, usually refers to light with a color temperature above 5300K, which has a bright, stable, and positive feeling, and keeps people clear and focused.
The psychological impact of glare
Glare refers to the visual condition that causes visual discomfort and reduces the visibility of objects due to unsuitable brightness distribution or extreme brightness contrast in space.
Glare is generated in the field of view, which interferes with the brightness and information content of the viewing area of the human body, or makes the human eye feel uncomfortable, which may cause disgust, discomfort, or even loss of vision, thereby stimulating inner restlessness and affecting mental health.
The glare index is usually expressed by UGR (Uniform Glare Rating), which was proposed by Sorensen in 1987 and adopted by the International Commission on Illumination (CIE) in 1995, and then recommended for international applications. The human eye perceives each glare index of glare as follows:
- UGR25: unbearable glare
- UGR22: A little uncomfortable feeling
- UGR19: Slight glare, tolerable
- UGR16: Slight glare, negligible
- UGR13: little glare, no uncomfortable feeling
- UGR10: no glare
Therefore, when we design healthy lighting for event venues, it is the best choice to control glare below 16.
Is sunlight healthy?
In the long evolutionary process of human beings, a very sensitive, intricate, extremely precise, and very harmonious automatic regulation system has gradually formed with the sun, which can develop harmoniously and sequentially under natural sunlight.
Sunlight is the most natural light. It existed on the earth before humans created artificial light. For animals and plants, it is undoubtedly healthy light.
1、Effects of sunlight on the human body
- Proper exposure to sunlight can make the human body produce vitamin D, and the sunlight is the best natural source of vitamin D. Vitamin D helps strengthen human bones and teeth.
- Appropriate exposure to sunlight can lower blood pressure. When sunlight hits the human skin, the body will release nitric oxide into the blood. This compound can lower blood pressure and improve heart health.
- Studies have shown that proper exposure to sunlight can increase serotonin, which can help people avoid seasonal affective disorder (SAD), and can also help people with anxiety and depression, especially when combined with other treatments.
For more details on the impact of sunlight on the human body, see Wikipedia “The Effects of Sunlight on Health”.
2、What is the color temperature of sunlight?
The color temperature of sunlight is not constant, it changes with time, and the circadian rhythm of the human body is also formed by the change of color temperature of sunlight.
The picture above shows the color temperature changes of sunlight at different times of the day. It emits a warm glow at sunrise/sunset, giving people a warm and warm feeling. The color temperature gradually becomes colder and whiter, and people are most energetic and focused at noon.
Now all people-oriented lighting is based on sunlight as the standard, and the light source close to the color rendering index of daylight is the best light source. Many indoor lights adjust the display color temperature according to the change in daylight color temperature, to make the human body achieve the purpose of the circadian rhythm.
What is the light of health?
Through the above analysis, we can conclude what is healthy light for the human body. From the two aspects of physiology and psychology, it can be divided into a narrow sense and a broad sense of healthy light.
- Healthy light in a narrow sense:
- Lamps that can emit light similar to sunlight, that is, the spectrum is similar to sunlight, the color temperature is similar, and the color rendering index is similar. As we all know, sunlight is the healthiest light. Light keeps the human body in a healthy state.
- Since daylight has different color temperatures in different periods, which affects the circadian rhythm of the human body, to ensure that the human body rhythm is not affected, healthy artificial light needs to provide different color temperatures for the body in different periods.
- Health light in a broad sense:
- Appropriate brightness: use high brightness in workplaces, use low brightness light in leisure places
- Appropriate color temperature: homes, residences, dormitories, and hotels use warm light; shops, hospitals, offices, restaurants, and restaurants use neutral light; offices, meeting rooms, classrooms, design rooms, library reading rooms, and exhibition windows Cool shades.
- Glare is an important factor affecting physical and mental health. Excellent glare control light is also an evaluation standard for healthy light.
Healthy light in different places
Healthy light is not static. We need to design lights with different color temperatures, illuminance, and color rendering index at different times and in different places, according to the rhythm and law of the human body’s day and night activities, to ensure the human body’s work, study, life, rest, etc. Healthy To promote people’s mental health and physical health from the inside out.
Below we will list some healthy light requirements for common places for your reference.
1、workplace:
Workplaces are usually: offices, meeting rooms, design rooms, etc., where it is necessary to complete work tasks efficiently, keep focused, and keep a clear mind. At this time, we not only need bright light, but also a light that contains more blue light, just like noon sunshine. In addition, it is also necessary that there is no glare that interferes with the line of sight in the space.
- Illumination: Desktop 300LX-500LX
- CCT:4000K-5500K, the data shows that the color temperature in this range contains more blue light. While maintaining focus, working for a long time will not fatigue the eyes and cause damage to the eyes.
- CRI: higher than RA90, usually a better color rendering index is better for eye protection, although RA80 has met the regulatory requirements, for the sake of health, we recommend using lamps above RA90+ for the first time.
- UGR: The healthiest value is undoubtedly less than 10, usually the two values of 13 and 16 are acceptable to the human eye.
2、Living place:
Living places are usually: commercial shops, restaurants, exhibition areas, and other places. We may need to clear our minds, or we may need to relax our bodies. Usually these activities are between work and rest, and have no impact on human body rhythm. At this time, light There is no clear requirement for the color temperature of the LED display. The illuminance perceived by the naked eye should be within the acceptable range of the human eye. Also in order to maintain the health of the human eye, we still do not allow glare that interferes with the line of sight.
- Illumination: 100LX-1000LX
- CCT:3000K-5500K. We do not have obvious requirements for blue light in living places. We usually set high color temperature light in areas that need to be focused, and low color temperature light in areas that need to relax.
- CRI: higher than RA90, usually a better color rendering index is better for eye protection, although RA80 has met the regulatory requirements, but for the sake of health, we recommend using lamps above RA90+ for the first time.
- UGR:The healthiest value is undoubtedly less than 10, usually the two values of 13 and 16 are acceptable to the human eye.
3、Learning place:
Learning places are usually: ordinary classrooms, book reading rooms, electronic reading rooms and other places, which require focused study and reading, and keep a clear mind just like workplaces. At this time, we need bright light and light containing more blue light , and no glare that interferes with vision.
- Illumination: Desktop 300LX-500LX
- CCT: 4000K-4500K, the color temperature in this range is between cool light and warm light, which ensures a clear mind and is more conducive to eye health, so you won’t feel eye fatigue if you focus on studying for a long time.
- CRI:higher than RA90, because you will be more focused during the learning process, and considering the eye protection of minors, it is recommended to use lamps above RA90/+. Compared with adults, the eyes of minors are more fragile. This is what we need to pay attention to.
- UGR: The healthiest value is undoubtedly less than 10, usually the two values of 13 and 16 are acceptable to the human eye.
4、resting place:
Rest places generally refer to homes, apartments, hotels and other places that need to rest and sleep. We need a quiet, relaxed and comfortable environment to help us sleep. At this time, we need low illumination and low color temperature to avoid lamps that keep our minds excited and affect sleep. , glare that interferes with the line of sight is also not allowed.
- Illumination: 100LX-200LX
- CCT: 2700K-3300K, according to the circadian rhythm of the human body, when we need to sleep, we should stay away from blue light, which requires low color temperature light.
- CRI: higher than RA90, usually a better color rendering index is better for eye protection, although RA80 has met the regulatory requirements, but for the sake of health, we recommend using lamps above RA90+ for the first time.
- UGR: The healthiest value is undoubtedly less than 10, usually the two values of 13 and 16 are acceptable to the human eye.
It can be seen from the above that the two fixed factors of healthy light are the glare index and the color rendering index, while the illuminance value and color temperature value vary with different places and different times.
The above is our knowledge sharing about healthy light, hope it will be helpful to you.
