Take a colorless and transparent wine bottle with a diameter of about 7cm, fill it with clean water, and plug it tightly.Then put a flashlight flat on the table and let its beam directed at you.Then put a stack of books between you and the flashlight. The height of the books is about five to six centimeters.The distance between the book and the flashlight is about ten centimeters.Then you bend down as shown in the picture, making your eyes look horizontally along the top of the book. At this time, the stack of books just blocks the light from the flashlight.Keep your head still and place the prepared water bottle horizontally between the book and the flashlight.Through the top of the water bottle, you can see the light bulb on the flashlight again.This is because the refraction of water makes you feel that the light bulb rises.
Figure 2
The sun is about 150 million kilometers from the earth.The earth is surrounded by a thick atmosphere. When sunlight enters the atmosphere from vacuum, it will be refracted, which is very similar to the above experiment.The refraction of the atmosphere can raise the sun by 35 minutes.The angle of the sun's circle to the observer on the earth is exactly 35 minutes, so when you see that the lower edge of the sun's circle has just left the horizon, actually its upper edge is still below the horizon.
Figure 3
People often compare light waves to water waves because there are many similarities between them.In Figure 3, we putlight waveDraw it like a water wave, and use some horizontal lines to show the ripples of light waves in the process of traveling.When the light slants into the glass, one side of a ripple first touches the surface of the glass. Since the light in the glass moves slower than in the air, the ripple side slows down first and the ripple bends.When all the ripples enter the glass block, it will go straight again.It can be seen that the bending of light only occurs at the moment when it passes through the interface.
By Dutch mathematicianssnell It was discovered thatRefraction phenomenonMedium, OKRefraction rayThe law of direction.When light from the firstmedium(refractive index none）Injected into the second medium (refractive index ntwo）On the smooth interface, part of the light enters the second medium from the first mediumrefraction。Experiments show that: (1) The refracted light is located at the incident light and the interfacenormalIn the determined plane;（2）Refracting lineAnd the incoming rays are respectively on both sides of the normal;（3）Angle of incidenceSine sum of iRefraction angleThe ratio of sine of i 'toRefractive indexOne for certain two mediaconstant.
Figure 4
In a nutshell, light is created bylight speedLargemediumThe refraction angle is less thanAngle of incidence；The refraction angle is larger than the incidence angle when entering the medium with high light speed from the medium with low light speed.
This law isgeometrical optics The basic experimental law of.It is applicable to uniform isotropicmedium。All kinds of optical instruments used to control the optical path and image are mainly based onRefraction of lightandReflection law。This law can also be based on thewaveConcept derivation, so it can also be applied to radio waves andacoustic waveAnd so on.
When light rays are refracted through the interface of two media, determineIncident lightIt is one of the basic laws of geometric optics, and it is related to the propagation direction of refraction ray.As shown in Figure 4, the incident light and the passing lightPoint of incidence's interfacenormalThe plane formed is called the incident plane, and the angle between the incident light and the refraction light and the normal is calledAngle of incidenceAnd refraction angle toθiandθtexpress.The law of refraction is: ① The refracted light is in the incident plane. ②Angle of incidenceAnd refraction anglesineThe ratio is a constantntwenty-oneMeans that
