The definition of "light" in physics?

Light can stimulate the retina to produce radiant energy of visual ability; The visible spectrum range of electromagnetic wave is 380 ~ 770 nm (10-9m).

Light is divided into artificial light and natural light. We can see the ever-changing multi-tone scene in the objective world because our eyes receive the light emitted, reflected or scattered by objects. Light is closely related to human life and social practice.

Light source: An object that can emit light by itself is called a light source. Light sources are divided into cold light sources and hot light sources;

Cold light source: it means to emit light without heating (or to generate heat at a very low temperature). Such as fireflies;

Thermal light source: refers to light emitting and heating (must be high temperature heat). Such as the sun;

Strictly speaking, light is a kind of radiation that can be observed by human eyes. Experiments show that light is electromagnetic radiation, and the wavelength range of this part of electromagnetic wave is about 0.77 micron of red light to 0.39 micron of purple light. Electromagnetic waves with a wavelength of more than 0.77 micron to about 1000 micron are called "infrared rays". Below 0.39 micron to about 0.04 micron is called "ultraviolet". Infrared and ultraviolet rays can't cause vision, but the existence of this luminous object can be measured and detected by optical instruments or photography. Therefore, the concept of light in optics can also be extended to infrared and ultraviolet fields. Even X-rays are considered as light, and the spectrum of visible light is only a part of the electromagnetic spectrum.

Light has wave-particle duality, that is, it can be regarded as a kind of high-frequency electromagnetic wave (10/2 ~1015hz), and it can also be regarded as a particle, that is, photon for short.

The speed of light replaced the platinum watch kept in the International Bureau of Metrology in Paris as the standard for defining "meter", and it was agreed that the speed of light was strictly equal to 299,792,458 m/s, which was consistent with the definition of meter and second at that time. Later, with the continuous improvement of the experimental accuracy, the numerical value of the speed of light changed, and the meter was defined as the distance traveled by light in 1/299792458 seconds.

Light is one of the sources of life on earth.

Light is the foundation of human life. Light is a tool for human beings to know the outside world. Light is an ideal carrier or media of information.

According to statistics, at least 90% of all information received by human senses from the outside world is transmitted through the eyes. ...

Light is essentially an electromagnetic wave, covering a wide electromagnetic spectrum (from X-ray to far infrared), but its wavelength is shorter than ordinary radio waves. Visible light visible to the naked eye is only a part of the whole electromagnetic spectrum.

When a beam of light is projected on an object, it will be reflected, refracted, interfered and diffracted.

Light travels in a straight line in a uniform medium.

Light waves, including infrared rays, have shorter wavelengths and higher frequencies than microwaves. Therefore, it is a natural and inevitable trend to develop from microwave communication in electrical communication to optical communication.

Ordinary light: Generally speaking, light is composed of many photons. Under fluorescence (ordinary sunlight, light, candlelight, etc.). ), there is no connection between photons, that is, different wavelengths, different phases, different polarization directions and different propagation directions, just like an unorganized and undisciplined photon army, all photons are stragglers and cannot act in unison.

When light is reflected, the reflection angle is equal to the incident angle. On the same plane, on both sides of the normal, the light path can be reversed.

Light incident obliquely from one medium to another will produce refraction. If the density of the injected medium is greater than that of the original light, the incident angle is less than the refraction angle. On the other hand, if it is less than, the incident angle is greater than the refraction angle. However, if the incident angle is zero and the refraction angle is zero, no refraction will occur. However, light refraction still occurs in the same inhomogeneous medium. Theoretically, it can be injected from one direction without refraction. However, due to the unclear boundary, it is generally divided into several levels and is not flat, so refraction will occur anyway. For example, looking at the calm lake bottom from the shore belongs to the first refraction, but seeing a mirage belongs to the second refraction. The function of convex lens and concave lens is due to the first refraction.

Laser —— A New World of Optics

In a laser beam, all photons are interrelated, that is, they have the same frequency (or wavelength), phase, polarization direction and propagation direction. Laser is like a disciplined photon army, acting in unison, so it has strong combat effectiveness. This is the main reason why laser can do many things, but sunlight, light and candlelight can't.

[Last name] Guang …

light

Light; Ray; Honor; Just; Naked; Scenery; Smooth;

light

Gu 'ang

( 1)

(I know. Oracle Bone Inscriptions glyph, "from fire, in people". Original meaning: light, light)

(2)

Homophonic [light; Ray]

The light is bright. -Shuo Wen

Light, swaying, swaying. It is also extensive and far-reaching. -"Interpretation of Name and Heaven"

Guang Qi and the sun and the moon. -"Songs of the South, Nine Songs, Gentleman in the Cloud"

People who can swim in the shadows share the light with the sun and the moon. -"Huainanzi Pearl Krabs"

The sun and the moon are shining brightly. -Huai Nan Zi Ben Jing

The light of the country -"Yi Guan"

The night is still early, and the lights of the court. -"Poetry Xiaoya Ting Liao"

Push this ambition, although it is as glorious as the sun and the moon. -Historical Records and Biographies of Qu Yuan

Those who are far away from others have their own glory. -Zuo Zhuan and Zhuang Gong for twenty-two years

Glory of light. -"Mandarin Jin Yu"

Let the light shine. -Mencius

The mountain has a small mouth, as if there is light. -Tao Jin Yuanming Peach Blossom Garden.

A ray of red light came from the bridge, pointing to the west of the city. -Shao Qing Heng Chang's Biography of Yandian History

(3)

Another example: sunshine; Lighting; Reflected light (reflected light); Colored light (colored light); Morning light (early morning sunshine); Dawn (morning sunshine); The lights are shaking (flashing)

(4)

Color; Glory [color]

My concubine has embroidered waist and gives birth to light. -"Yutai Ancient Poems and New Poems Dedicated to Jiao Zhongqing's Wife"

Moths have uncomfortable faces and dark sleeves. -Don Lee Wei Chao's Liu Yichuan

(5)

Another example: mercerization; Glossy (bright and moist); Light color (glossy color); calender

(6)

Glory; Reputation [honor; Glory]

The smell of food is the smell of my state. -"Poetry, Qifeng, Nanshan has a platform"

Even my face is dull. Scholars

It is difficult for a scholar to live in the world and look forward to fame and fortune and moral journey. -Don Han Yu's Original Extinction

(7)

Another example: winning glory for the country; Exposure; Light pet (glory; Credit); Guangguo (glory for the country); Guangtian (Guanghua reaches the world); Guanglong (glorious age); Light rotten (bright and bright); Light crystal (luster); Guanghe (brilliant)

(8)

Time [time]

At the beginning of the screen, I worry about my thoughts, and I like my feelings. -Bao Zhao's "Guan Lou Fu" in the Southern Dynasties

(9)

Another example is: inch light (short time); Time flies (day by day). Time flies: [Time] is drifting away); Time flies (time flies). Describe how fast time passes); Time flies, ie the sun is fleeting. Describe how time flies)

( 10)

[scenery] [scene]

The sky is up and down, and there is a blue sky. -Song Fan Zhongyan's "Yueyang Tower"

( 1 1)

Another example is: scenery; Yamamitsu

( 12)

Grace; Benefits [favor] such as: light; Exposure; I'm sorry

( 13)

Especially the celestial bodies such as the sun, the moon and the stars. Such as: guangyue (heaven and earth. Light: stars. Yue: He Shan)

( 14)

Greet the visitors. The existence of]

Four old gentlemen, I care about Xiao Yuan today. What virtue can I have? -Ming Sang Shaoliang, "Sima Rutong, narcissistic"

light

Gu 'ang

( 1)

Bright, bright [bright]

The sword is like a thousand dollars, light and fresh. -Three Kingdoms Shu Cao Zhi's "Mingdu"

(2)

Another example is: smooth (smooth); Bright; Light eyes (big eyes with gods); Lighting (strong light); Smooth (bright and moist)

(3)

light

Let's go.

( 1)

Sun, fire, electricity, etc. Emit dazzling and bright things, and you can see objects: yang ~. Month ~. It's on fire. ~ Hua (brilliant).

(2)

Honor: ~ Pro (honorific, meaning that the arrival of guests brings glory to the host). ~ gu. ~ reply.

(3)

Make it stand out: ~ big. ~ zong yaozu.

(4)

Scenery: spring ~ bright and beautiful.

(5)

Smooth: ~ slippery. ~ Jay. ~ ze.

(6)

It's over, there is nothing left: kill ~ burn ~. Eat ~ use ~.

(7)

Exposure: ~ arm.

(8)

Single, only: ~ one breath left.

(9)

Last name.

Zheng code: KOGR, U: 5 149,: B9E2.

Number of strokes: 6, radical: er, number of strokes: 243 135.

Light; Ray; Honor; Just; Naked; Scenery; Smooth;

light

1 bright. Su Wen Yi Jing Hua Qi: "To be close to the patient, to observe life and death, to be suspicious and to know about it is like the light of the sun and the moon."

2 reveal, reveal. "Su Wen Wang Xu Bing": "The monarch and the minister who lost the ceremony will be proud of taking the exam and get what they want."

③ Everbright. Lingshu Root Knot: "Regulating Yin and Yang, Essence is Light."

The speed of light is 300,000 kilometers per second.