Part 9 ~ Relationship between black body radiation and light ~

Principle of blackbody radiation

A "black body" is a theoretical object that completely absorbs all incident light and re-emits light of all wavelengths through thermal radiation.

A characteristic of blackbody radiation is that the wavelength distribution of radiant energy depends on temperature, and the higher the temperature, the more light with short wavelengths is emitted.

The curve that represents the radiation characteristics of this blackbody is called the "Planck radiation curve."
The shape of the Planck radiation curve changes depending on temperature; at high temperatures, light with short wavelengths becomes dominant, and at low temperatures, light with long wavelengths becomes dominant.

When a blackbody is heated, thermal energy is emitted outside in the form of electromagnetic waves depending on the temperature.
As the temperature (absolute temperature) of the black body increases, the spectral distribution of the emitted electromagnetic waves changes color: red-black → orange → yellow-orange → yellow → white → blue-white.

In this way, blackbody radiation is closely related to the color temperature of light. Blackbody radiation is caused by the thermal vibrations of an object and is very important for understanding its relationship with the color temperature of light.

Relationship between color temperature and blackbody radiation

Color temperature is one of the indicators that expresses the color of light, and is mainly used to express the color of artificial lighting (LED, fluorescent lights, etc.) and sunlight.
On the other hand, blackbody radiation indicates the properties of light emitted by an object and expresses the radiation at a specific temperature.

The relationship between color temperature and blackbody radiation is important in understanding the properties of light sources.
Color temperature describes the "warmth" or "coolness" of light, and blackbody radiation models the spectral distribution of a light source.
If the color temperature of the light source is high, the light will have a more bluish tone.
This is because a high-temperature blackbody predominantly emits light with short wavelengths.
For example, sunlight on a clear day has a high color temperature, giving a bright and cool atmosphere.

On the other hand, a light source with a lower color temperature will have a more reddish tone.
This is because a cold blackbody predominantly emits light with long wavelengths.
Examples include warm lighting and candlelight.
Even if the actual light source is not a blackbody, its spectral distribution may approach blackbody radiation.
For example, light from an incandescent bulb has a color temperature of approximately 2,700K and a spectral distribution close to blackbody radiation.
On the other hand, fluorescent lights and LEDs have different spectral distributions depending on their color temperature.
This shows that the tones of light vary depending on the color temperature.

In fields such as lighting and displays, it is possible to achieve different light qualities by adjusting color temperature.
By understanding the relationship between the color temperature of a light source and blackbody radiation, it is possible to create more effective lighting designs and visual expressions.

For example, by choosing a warm color temperature, you can create a warm atmosphere in living spaces, restaurants, etc.
On the other hand, cool color temperatures are suitable for offices, hospitals, etc. where brightness and vividness are important.

Research on blackbody radiation and color temperature

Research on blackbody radiation and color temperature has made various contributions to the real world.
Its applications are wide-ranging and play an important role in fields such as lighting design, image processing, medicine, and environmental control.

・Lighting design

Research on color temperature in lighting design has revealed its impact on the living environment and work efficiency.
For example, by appropriately setting the color temperature of lighting equipment, you can not only make your living space or office environment more comfortable, but also contribute to improving visibility and reducing eye fatigue.
By setting an appropriate color temperature, it is possible to take into account the psychological effects on people.

・Image processing

In the field of image processing, accurate adjustment of color temperature is important.
Adjusting the color temperature of cameras and displays has a significant impact on the hue and appearance of images.
Research into color temperature has made it possible to improve the color reproduction and fidelity of images.

・Medical care

Research on color temperature is also essential in the medical field.
Accurate color reproduction is required in operating rooms and clinics.
In particular, accurately capturing skin conditions and tissue tones is essential for diagnosing medical conditions and evaluating the effectiveness of treatments.
Research on color temperature is advancing the debate about appropriate lighting settings and image processing techniques in medical environments.

・Environmental control

Research on color temperature is also useful in the field of environmental control.
For example, plants need light of the right color temperature to grow. In agriculture and plant factories, optimizing the color temperature of light can improve crop growth and yield.

Future of research on blackbody radiation and color temperature

Optical technology is constantly evolving and holds many possibilities for the future.
Advances in the latest optical technologies related to color temperature and blackbody radiation are expected to bring about revolutionary changes in our lives and industry.

For example, LED lighting is more energy efficient and its color temperature is easier to control, allowing more freedom in lighting design.
Additionally, with the spread of smart lighting systems, it will be possible to remotely control the color temperature and brightness of lighting, and automatically change the lighting scene and mood.

Furthermore, advances in color temperature control technology have made it possible to finely adjust the color temperature of individual lighting equipment and displays.
It is expected to not only reproduce a more natural light environment, but also create a light environment that directly affects people's health and productivity.

In recent years, light therapy has attracted attention, and treatment methods that utilize color temperature according to symptoms have been developed.
Using light with a specific color temperature and wavelength, it is expected to improve sleep disorders, poor physical condition, and decreased concentration.
In this way, treatment methods that use light that do not put a burden on the body may expand.

Furthermore, advances in research and technology related to color temperature and blackbody radiation are also playing an important role in architecture and urban planning.
Effective placement of lighting and adjustment of color temperature can improve the comfort and safety of living and public spaces.
The development of sustainable lighting technologies also improves energy efficiency and reduces environmental impact.

~summary~

Color temperature and blackbody illumination are important concepts regarding light temperature and its applications.
Color temperature refers to the color of light, and blackbody irradiation refers to the properties of an ideal heat radiator.
These concepts are widely used in the lighting industry and photography, and are also related to lighting effects and energy efficiency.

Color temperature also affects visual perception and psychology, making it an important factor related to quality of life and health.
Research and applications related to color temperature and blackbody irradiation will continue to advance, and it is expected that this will contribute to creating a more comfortable and sustainable light environment.





Written by: BARREL Editorial Department
Supervised by: Yuki Oe (Lecturer, Department of Lifestyle Design, Faculty of Human Culture, University of Shiga Prefecture)
Lecturer at the University of Shiga Prefecture, Faculty of Human Culture (Department of Lifestyle Design).
She specializes in architectural environments, light environments, lighting environments, and color environments.
She is a member of the Architectural Institute of Japan/Illumination Institute of Japan.
After completing her doctoral course at Nara Women's University Graduate School of Humanities, she worked in technology planning at Sharp.
She worked as an assistant professor in the Faculty of Science and Technology at Tokyo University of Science and as a part-time lecturer at Osaka Jonan Women's Junior College before reaching her current position.