when light rays pass through each other (in air)do they bend?

Answer 1

BRILLIANT. What a fantastic question. Honestly, you have excited me now.

Have you ever heard of a solitary wave (AKA the Soliton)? If not, let me tell you a story....

In 1844 a man (named John Scott Russell) noticed a curious phenomenon with a water wave on a scottish canal. Unlike normal waves, this wave only had one crest and no troughs. In fact, it appeared to be a mound of water sitting on top of the water's surface. This wave travelled down the canal not losing its shape for a considerable distance (until the corners in the canal dispersed it). This was the worlds first observation of a soliton.

There are two (basic) types of soliton but they both work in similar ways. I will describe them both here with reference to light:

1) Temporal solitons. These a pulses of light who do not spread as they pass through a medium. Normal pulses of light would spread due to dispersion (the different frequencies of light contained in the broad-bandwidth of the pulse all travel at different speads, so the pulse would spread). If you ramp the intensity high enough, the nonlinear part of the constitutive relationship becomes significant as it is related to the cubic of the electric field (whereas the linear term is related linearly to the field). Almost all media are nonlinear such that, when you ramp the intensity high enough, a solitary pulse can propagate. The spread of dispersion is balanced by the nonlinearity!

2) Spatial solitons. These are my speciality. Unlike temporal solitons, where the angular-frequency of the light is significant (as it defines the dispersion), spatial solitons act like a beam. They are continuous (or pulsed) sources of light that, unlike normal beams of light, do not spread! That's right, they are a perfect beam of light that never spreads. Again, you have to ramp the intensity up high enough, but if you do the beams of light start to self-focus because the intensity affects the refractive index such that the medium acts like a waveguide.

Let's first of all consider temporal solitons. Two temporal solitons colliding will not affect each other.

Now, lets consider spatial solitons. The collision of two spatial solitons will not produce a significant affect (except maybe they will become one beam if the intensity is sufficiently high).

Two spatial solitons IN PHASE travelling parallel to each other will repel each other so that the beams will bend away from each other.

Two spatial solitons OUT OF PHASE travelling parallel to each other will attract each other so that the beams will bend towards each other.

So, in this way, the two beams of light (that technically aren't touching) can communicate with each-other and bend. Air is weakly nonlinear, but ramping the intensity up really high (I mean, more than military-weapons power high) will cause it to become sufficiently nonlinear for a spatial soliton to propagate.

BUT, we need to be clear about this. Your question was about light RAYS, i.e. the paths the individual photons take. RAYS are different from BEAMS.

Whilst BEAMS will bend, RAYS will not (with the exception of strong gravitational or electromagnetic fields). The reason a beam of light is different from a ray of light is that, technically, if you perform a fourier transform on a beam to see what wavenumbers exist you will find that they ALL exist in the beam. There is an infinite spread of wavenumbers in a beam, each wavenumber representing a single ray.

So, whilst two beams may be travelling parallel, there will be rays of light travelling in all directions (of varying intensities) such that the two beams can communicate (and bend). The rays themselves don't bend.

Now, I want to make this clear. This is not 'only a theory' or 'science fiction' or any other put-down people might light to make. This is FACT. It has been SHOWN. It has been OBSERVED and REPRODUCED. The theory behind it has been EXPLAINED and experiments with it are ONGOING.

Beams of light can bend. Rays can not.

In your case, I think you were actually talking about beams (although you erroneously called them rays) because I remember at school the teacher would ALWAYS get it wrong.

If you are interested, look up Kerr Nonlinearity, or ask your teacher about Kerr Nonlinearity.

Answer 2

When the light rays travel through the one medium then they have fixed wavelength. As each color have fixed wavelength in air they donot bend but there may interefernce of the light. However when medium changes this cause the light to bend.

Answer 3

Because light travels slower in optically dense substances. Imagine a wavefront coming down to hit the object at an angle. Imagine that the light is parallel so the wavefront is a straight edge. The edge that hits the object first slows down. The wavefront slews around towards the normal because the edge that is still in the air is moving faster. So the whole wavefront is rotated a bit.

Answer 4

No .. they don't interact