China’s ancient poems, idioms and sayings contain a wealth of physical knowledge. Here we will learn about the optical knowledge in ancient poems, idioms and sayings to deepen our understanding of the phenomenon of light.

1. Light propagates along straight lines

1. Sitting in a well and observing the sky

Analysis: The frog at the bottom of the well sees a very small sky, which is caused by the linear propagation of light.

2. Immediate effect

Analysis: If you put up a bamboo pole in the sun, you will see a shadow immediately. It is precisely because light propagates in a straight line that the bamboo pole blocks the light and forms a shadow.

3. A leaf blocks your eyes, and you cannot see Mount Tai.

Analysis: A leaf blocks your eyes, and you cannot even see the tall Mount Tai in front of you. What is used is the knowledge that light propagates in a straight line.

4. The dense shade of green trees makes the summer long, and the reflection of the tower into the pond. (From "Summer in the Mountain Pavilion" by Gao Pian, a poet of the late Tang Dynasty)

Analysis: The formation of "dense shade" in the poem illustrates the straight line of light propagation; and "balcony reflection" is a virtual image formed by the reflection of light.

5. On a day when there are many peaks and clever obstacles, the river is far away and seems to be floating in the sky. (From "A Tour of Jiangshan" by Su Shi of the Song Dynasty)

Analysis: "On a day when there are many peaks and clever obstacles", why is the sun's rays blocked by the mountain peaks? The straight line of light Caused by transmission.

6. The clouds are pushed out as many peaks as possible, and half of the river is clear as daylight. (From "Bo Zhang Town" written by Yang Wanli in the Song Dynasty)

Analysis: The main idea of ??the poem is, why do we have to push away the floating clouds on the mountainside in order to see the peak? Sunlight can only penetrate through the cracks in the clouds to illuminate the river surface. They all use light to propagate in straight lines.

2. Reflection of light

1. Flowers in the Mirror and Moon in the Water

Analysis: The images of objects in water and mirrors are virtual images, so it is said that you cannot pick the moon in the water and you cannot pick flowers in the mirror.

2. When Zhu Bajie looks in the mirror, he is not a human being inside or out.

Analysis: According to the rules of plane mirror imaging, the image formed by a plane mirror is equal in size to the object, and the object image is symmetrical. Therefore, the image Zhu Bajie sees is exactly the same as himself, and he is still a human being. Pig statues are naturally "not human inside and out".

3. Jade is useless if it is not polished

Analysis: Before the jade is polished, its surface is uneven and the light is diffusely reflected. After the jade is polished, its surface is smooth and the light is specularly reflected.

4. Raise a glass to invite the bright moon, and the shadows form three people. (From "Drinking Alone under the Moon" by Li Bai of the Tang Dynasty)

Analysis: "Toast a glass to invite the bright moon" shows that the moon forms a virtual image in the wine glass, which involves the imaging of a plane mirror .

5. Baochai shines brightly on the head, and the shape can be discerned in a mirror. (From "Giving a Wife" written by Qin Jia of the Han Dynasty)

Analysis: "Baochai shines brightly on the head" means that the light reflected by the jewelry enters the human eye. , looks particularly dazzling; "A clear mirror can identify shapes" uses the knowledge of plane mirror imaging.

6. Holding the moon in the water in hand, the fragrance of flowers fills the clothes. (from "Spring Mountain Night Moon")

Analysis: "Holding the moon in the water", why there is a moon in the water, the physical knowledge involved is the image of a plane mirror.

7． The bright moon is thousands of miles away, the floating light jumps into the gold, and the still shadow sinks into the jade (from "Yueyang Tower" written by Fan Zhongyan in the Song Dynasty)

Analysis: The "bright moon" is because it reflects the sun's light, and the moon itself does not emit light; "the floating light jumps out" "Gold" means that the sun's rays are reflected by the water surface, making it look like the lake surface is glowing with golden light; "quiet shadow sinks into the jade" is a virtual image formed by reflection.

8. The sky is wide and the trees are low, and the clear moon on the river is close to people. (From "Su Jian De Jiang" by Meng Haoran of the Tang Dynasty)

Analysis; "The clear moon on the river is close to people" means that the moon forms a virtual image in the water, the author It feels like the distance between the virtual image of the moon and the moon is very close. In fact, it is not in line with scientific principles, because the characteristic of plane mirror imaging is that the distance between the object image and the mirror surface is equal, so there is no "near person".

3. Refraction of light< /p>

1． Mirage

Analysis: Light is refracted through air with uneven density, and what you see is a virtual image.

2. The sun can be seen in a drop of water, and the spirit can be seen in one thing.

Analysis: A drop of water is equivalent to a convex lens. According to the imaging rules of convex lenses, a real image of the sun can be seen through a drop of water.

3 ． The lonely smoke in the desert is straight, and the sun sets over the long river. (From "The Envoy to the Fortress" by Wang Wei of the Tang Dynasty)

Analysis: The "setting sun" the author sees is not the actual sun, but the light passing through it. When the atmosphere is uniform, a virtual image formed by refraction occurs, and the actual position of the sun is below the horizon.

4. If the pond is clear, one suspects the water is shallow. If the lotus moves, the fish will scatter. (From "Diaoyu Bay" written by Chu Guangxi of the Tang Dynasty)

Analysis: "The pond is clear, one suspects the water is shallow" means that the water in the pond is crystal clear, making people suspicious. It is very shallow because light is refracted when it enters the air from water. What we see is a virtual image at the bottom of the pool.

4. Dispersion of light

1. The setting sun shines back on Taohuawu, and the catkins are flying in patches of red. (From "The Rain Window Disappears" by Niu Yingzhi in the Qing Dynasty)

Analysis: The catkins are originally white, but the poem says that they are "flakes of red". "Red". The reason is that sunlight is composed of seven colors of red, orange, yellow, green, blue, indigo and purple. Red peach blossoms reflect red light and absorb other colors of light. When catkins pass through a red peach blossom forest, only The red light is reflected, and the reflected red light hits the white catkins, and the catkins naturally show a light red color.

2. On this day last year, in this door, the human face and the peach blossoms reflected the red color. (From "Tidu Chengnanzhuang" written by Cui Hu of the Tang Dynasty)

Analysis: We see that the color of an object is determined by the color of the reflected light. Red The peach blossoms only reflect red light, and the red light reflects onto the human face, making the human face look red.