Since light is a wave, why do two beams of light cross on the screen without producing interference

From your high school, college of electricity, electromagnetism.

In the textbook you can know: electromagnetic fields.

The laws of physics are linear. That is, the solution of two electromagnetic field equations, such as two columns of waves, is still the solution of the electromagnetic field equation when superimposed. The two columns of light waves pass through each other, propagate independently, and do not affect each other.

But when you mention photons, we get into quantum physics.

of the world. Quantum field theory.

There are some effects that can cause photons to collide with photons. Professionals can calculate the probability of a collision by using the following diagrams:

This is known as the Feynman diagram. The curved lines on the outside represent lightThe transmission of the sub, the solid line inside represents the electron. What they mean is that there is no direct interaction between photons and photons

It is not possible for two photons to collide directly; But a photon can turn around and change into a pair of "imaginary" positrons and negatives, and the electron can collide with another photon, and then the pair of imaginary positrons and negatives can be annihilated into a pair of photons.

The chances of such a collision are small when the frequency of light is lessGamma raysband, it's very, very small. After all, when the energy of a photon is relatively close to the ability to produce a true pair of positive and negative electrons, the possibility of producing a "virtual" electron pair is relatively high. Therefore, it is not easy to observe the violation of independent propagation of light in general experimentsPrinciple.

But when you mention photons, we enter the world of quantum physics. There are some effects in quantum field theory that can cause photons to collide with photons.

Professionals can calculate the probability of a collision using the following diagrams: This is known as a Feynman diagram. The curved line on the outside represents the transmission of photons, and the solid line on the inside represents electrons.

What they mean is this: there is no direct interaction between photons and photons, and it is impossible for two photons to collide directly;

But a photon can turn around and change into a pair of "imaginary" positrons and negatives, and the electron can collide with another photon, and then the pair of imaginary positrons and negatives can be annihilated into a pair of photons.

Light, water, and sound waves can all interfere. When two light waves interfere, some areas will be brighter and some areas darker, i.e., interference fringes appear.

When the thickness of the air layer is an integer multiple of the half-wavelength of the light in the air, the vibration strengthens and bright streaks appear; When the thickness of the air layer is several times the odd number of times the wavelength of light in the air, the vibration weakens and dark streaks appear, so this interference is called equal thickness interference.

The interference fringes of the tonning ring are produced by the interference of two rays of light sandwiched between the upper and lower surfaces of the air layer between the lens and the smooth plane.

Young's double-slit experiment with electrons shows that electrons can also appear interference fringes on the screen! From this, physicists conclude that sometimes, electrons behave like waves, and one electron passes through two slits at the same time, and then it interferes with itself!

Therefore, electrons and light, both as particles and waves, have the dual properties of particles and waves, which is what quantum mechanics tells us: microscopic particles, including electrons and light, have "wave-particle duality".

The reason why two beams of light cross the screen and do not produce interference fringes is because their beams are different.

When you mention photons, we enter the world of quantum physics. There are some effects in quantum field theory that can cause photons to collide with photons.

The solid line inside represents the electron. What they mean is that there is no direct interaction between photons and photons

I think it's because these are not the only conditions for interference fringes.

In the Young's double-slit interference experiment, when the light source moves up and down, the interference fringes move down and up (in the opposite direction of the former).

The interference must first coherent light bypass the obstacle (in fact, diffraction) and then superimpose on each other, forming a streak of light and dark.

The double slit is vertical, horizontal, small in size, easy to bypass the light (diffraction), located on the left and right sides; Each seam, while the size of the vertical direction, is not easy for the light to go through, so there is no light up and down. Eventually, the light on the left and right sides of each vertical slit is superimposed on each other, forming light and dark stripes, of a nature and parallel seams.

Summary. We'll be happy to answer for you. This is because it is very difficult to accomplish the destructive polymerization of two beams of light during the experiment, just as it is difficult to remove two parallel lines from a serpentine path curve and then place them parallel again in another spatial position.

We'll be happy to answer for you. Because in the experiment of the Spring Sun Summoning Journey, it is difficult for Kai to complete the destructive aggregation of two split beams, just like taking two parallel lines from a serpentine path curved tube, and then it is difficult to place them parallel again in another space.

Destructive interference is in the interference of light, where the amplitude of two light waves is equal to zero. For example, if a monochromatic beam of bionic light is split into two beams with a beam splitter with limbs, and then they overlap in a certain area of space, it will be found that the light intensity in the overlapping area is not evenly distributed. The brightness varies depending on its position in space, with the brightest place being oversized and the darkest place having zero light intensity.

We can understand the beam as two parallel extension of the S line, when the light is split and then converged, it becomes two cross-extended twist beams, the small ring on the twist is the part that is lighter than the original light, and the large ring is the part that becomes darker after dispersion.

This is because you're confusing the order, it's based on the difference in optical pathlength.

is a wavelength that causes the period of its vibration to change once, and the resulting two bright stripes spacing formula, rather than from the spacing formula comes out of them is a wavelength!!

This is easy to illustrate, do you think that even if you don't interfere, a simple column of waves, his two adjacent vibrational strengthening points, how far apart? Isn't it just a wavelength? Why one wavelength and not several? Isn't that very simple, and that's how wavelength is defined.

In the same way, since you are adjacent to the two bright stripes, it is the two adjacent vibration strengthening points, since it is the adjacent two vibration strengthening points, naturally when the vibration of the two light waves is strengthened, the previous vibration strengthening may be the crest of the two waves is several wavelengths apart, and the latter adjacent vibration strengthening point may be the difference between the peaks of the two columns of waves by several wavelengths plus 1, note that only one is added, because they are adjacent, not spaced. And then how much is the difference between the strengthening positions of these two adjacent wavelengths, and you subtract the difference between the optical path difference of the former one and the optical path difference of the latter one, isn't that exactly one wavelength? If you still can't understand, I suggest you go down and take a good look at the double slit interference.

How is the formula derived.

Light is an electromagnetic wave, and like other waves, light also has interference phenomena and the principle of superposition applies. Where two columns of light waves reinforce each other, they should appear brighter than one column; Where two columns of light waves weaken each other, it will appear darker than when there is only one column of light waves; When the vibrations caused by the two columns of light waves cancel each other out, these positions should appear completely black. The appearance of such light and dark streaks is the "interference phenomenon of light".

Is it possible that any two beams of light can interfere with light? No. Interference can only occur if two columns of light waves are of exactly the same frequency, they vibrate in the same direction, and there is always a definite relationship between the pace of their vibrations (optically called "constant phase difference").

Even if the frequency is the same (e.g., the same 30W fluorescent lamp) and the direction is the same, the light emitted by two different points of a normal light source cannot maintain a definite relationship in the "phase", so it is still incoherent. The coherence of the laser is closely related to the monochromaticity and directionality of the laser. The better the monochromatic and directional light, the better its coherence must be.

We can take advantage of this coherence of the laser to concentrate its energy in a very small area of space, so the laser can concentrate very small to produce a large amount of energy, which can be used to initiate thermonuclear fusion. If nuclear fuel is made into a solid microsphere smaller than a small sesame seed, and then a laser is used as an igniter to irradiate it, the microscopic ball can be heated to a high temperature of hundreds of millions of degrees, and the energy density it produces is as high as 1 quadrillon per cubic centimeter. Such a high energy density is equivalent to the energy density produced by dozens of tons of explosives concentrated in a volume of 1 cubic meter, that is, it has reached the order of magnitude of the ultra-high energy density obtained when the atomic bomb was obtained.

Hologram is an example of the successful application of laser coherence. The laser is divided into two beams through the beam splitting device, and one beam of light is directly directed on the base piece, which is called the "reference beam"; Another beam of light is reflected by the photographed object and then hits on the substrate, which is called the "object beam". Two beams of light form interference fringes on the negative, so that the photosensitive negative is holographic**.

Holographic ** is not only realistic, three-dimensional sense is very strong, what is particularly wonderful is that when looking at holographic**, ** people change different viewing angles, you will see the scenery in different positions. What's even more amazing is that even if most of the holographic ** has been damaged, only one corner remains, and the whole scene can still be reproduced.

Interference of light Checking the flatness Why is the interference fringe of B biased to the left First of all, this detection method is the principle of equal thickness interference of the applied film (split tip). The distribution of interference fringes is only related to the thickness of the medium, and the same thickness corresponds to the same level of fringes, so it is called equal thickness interference. That is, the interference fringes should be the trajectory of the point of equal thickness of the medium, and when the plane is flat, the thickness changes uniformly, and the fringe is a straight line.

When there is a concave on the measured surface below, the fringe is the trajectory of a point of equal thickness, and the concave is the increase in thickness, so the thickness here is equal to the thickness of the place away from the splitting edge (where the thickness is 0), and the trajectory away from the splitting edge is biased here, and the overall situation is: the fringe is biased in the direction of the splitting edge.

If there is a convexity, you will know it, and it will be deviated away from the direction of the split.

Key points: equal thickness interference, the same thickness corresponds to the same level of stripes.

A. In the double-slit dry experiment of light, if the optical path difference is equal to the integer multiple of the wavelength, the vibration reinforcement will show bright fringes, and if the optical path difference is an odd multiple of half a wavelength, the vibration will be weakened and dark fringes will appear, so both bright and dark fringes are the result of light superposition, so A is wrong

b. According to x=ld

It can be seen that the distance between the bright stripes and the distance between the dark stripes are equal, so b is wrong c. If one of the seams is blocked, a single slit diffraction phenomenon occurs, so the light and dark stripes still appear, so c is correct

d. According to x=ld

It can be seen that the fringe spacing varies with the change of wavelength, and since the wavelength of yellow light is greater than that of green light, the interference fringe spacing produced by yellow light is larger than that produced by green light, so d is wrong

Therefore, c