*- In Radio amplitude modulation the interference-frequency is equal to the difference of the interfering frequencies

*- This applet demonstrate such interferences

*- Contrary to popular belief interference of Green and Red lights does not produce yellow light

*- How can 2 separate monochrome beams of light with different frequencies be made to interfere/modulate and produce a differential frequency?

*- I am interested in apparatus details of such a setup

Thanks in advance

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"They reasoned that an object situated at the center and related equally to the extremes in every direction can have no impulse to move in any specific direction. In fact, they compared the situation of such an object with that of a man violently but equally hungry and thirsty, standing at the same distance from food and drink and unable to decide in which direction to move." - Aristotle

This is the first I have heard that anyone might believe that the yellow sensation is the result of interference.

If I am not mistaken, ordinary light does not produce such interference patterns because it is incoherent. We would need laser beams to do this. It would be interesting to see how our eyes would respond if two different ultraviolet beams made a difference beat with a frequency in the visible-light range.
Try Googling "optical heterodyne".

It is a popular and true belief that green and red light together appear yellow.

The sense of color is a differentiation of and sumation of light frequencies due to chemical activation of separate receptors in the eye. In physics visible light frequencies are identified by ... frequency.

For audio and radio frequencies at least, the term beat frequency is commonly used to describe the sum and difference frequencies produced in the envelope amplitude modulated signal that results when mixing frequencies. The beat frequencies are only the strongest frequencies produced and other harmonics usually exist due to phase differences.

For light this would translate to interference and diffraction patterns whether due to simple phase difference as in standard monochromatic laser interferometry, or the mixing of wavelengths. Here you will see the amplitude modulated envelope as light and dark stripes, or see the beat frequencies produced as sidebands on the appropriate spectrum analyzer.

Homemade Laser Interferometer

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"Those who cannot remember the past are condemned to repeat it" - George Santayana

Find a keyboard, choose "organ," and play two adjacent notes in the lowest octave. Each of the notes may have a frequency of several hundred cycles per second, but the steady THRum-THrum-THrum is around 2 to 3 cycles per second.

Same with adjacent frequencies of light.

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol. A human.

Whoever says "perception is reality" is daft. It's merely an abstraction, and often not a very good one.

Thank you Hornblower. I have never valued terminology much. It's a big obstacle not to know what to search for in an IQ-less Search Engine.
I'm glad I asked.

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"They reasoned that an object situated at the center and related equally to the extremes in every direction can have no impulse to move in any specific direction. In fact, they compared the situation of such an object with that of a man violently but equally hungry and thirsty, standing at the same distance from food and drink and unable to decide in which direction to move." - Aristotle

Thank you for the link GORT,

I am interested in sinusoidal interference of lights of different frequencies.
That link seems to be about interference fringes of a single frequency of light.

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"They reasoned that an object situated at the center and related equally to the extremes in every direction can have no impulse to move in any specific direction. In fact, they compared the situation of such an object with that of a man violently but equally hungry and thirsty, standing at the same distance from food and drink and unable to decide in which direction to move." - Aristotle

Hi mugaliens,

Thank you for the reply.

The problem with lights of different sources seem to be that they do not readily mix/interfere.

So let's break down the issue to the following questions:

*- How would you mix 2 distinct laser beams of different frequencies such that they would produce sinusoidal interference.

*- Borrowing from GORT's link would the following produce sinusoidal interference between a green and a red laser?

**- A green laser is shone towards a CD case cover at 45 degrees
**- The transmitted light is reflected back from a perpendicular mirror on the other side
**- A secondary reflection from the other side of the CD case is projected on a wall
**- A red laser is situated at 90 degrees to the green beam and is shone such that it passes the CD case and is super-imposed on the green laser on the wall
***- Keep in mind that if I'm not mistaking even the fringe interference requires splitting of a single source of light and would not work if the 2 distinct laser lights of equal frequency are used

*- If there is anyway at all to achieve sinusoidal interference of light, how would the photon/particle point of view handle/explain this?

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"They reasoned that an object situated at the center and related equally to the extremes in every direction can have no impulse to move in any specific direction. In fact, they compared the situation of such an object with that of a man violently but equally hungry and thirsty, standing at the same distance from food and drink and unable to decide in which direction to move." - Aristotle

Sound is tri-modal. That is, the only characteristics of sound are the direction of travel, the pressure range (amplitude), and the frequency. It's the pressure, oscillating back and forth which we hear. For wavelengths significantlly larger than our ears, it does not matter their direction. This is why it doesn't matter very much where you place a subwoofer - it'll continue to do it's job. For wavelengths around the size of our ears and smaller, a sound's direction becomes increasingly important.

Light, however, is quadra-model. It has a direction, an amplitude, a frequency, and a phase. This is why light's polarity is as important as it's other characteristics.

If you take a monochromatic laser, split the beam, then polarize beam A along one axis, and polarize beam B along an axis that's 90 deg to the first, and recombine the beams, you get nothing (well, next to nothing, as polarization isn't 100% efficient).

The problem with polarization is that you don't know which way the e-beam is oscillating after polarization - up, then down, or down, then up.

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol. A human.

Whoever says "perception is reality" is daft. It's merely an abstraction, and often not a very good one.