About the components of light ?

I just learnt that light consists of electric and magnetic fields oscillating at right angles to each other . Now my question is that why can't the electric and magnetic components of light interact with matter. For example why does not the magnetic component in light interact with a external magnetic field and bend toward or away from it. Also how do we tell the direction of magnetic and electric fields in light . I know that this question might seem really dumb , but i seem to have a great difficulty in understanding light and would be really satisfied if some could give or direct me to a detailed explanation. Thanks in advance ..

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iceng2 years ago

Light can be considered quantas of photons or a wave the same as a microwave ExM propagation which is not affected by an external magnetic field but gravity can bend it.

kelseymh iceng2 years ago

Look up "Faraday effect" -- an external magnetic field affects the two opposite circular (elliptical) polarization states differently, with the result that a given plane polarization state will be rotated when traversing a field region.

iceng kelseymh2 years ago
iceng iceng2 years ago

And yes, a magnet B field is rotating polarized light enough to be observed and measured.

And as you point out it takes a refined instrument to make it visible.

As the early astro scientists trying to take meaningful pictures of starlight bending around our sun during an eclipse to prove Einstein's theory.

Both of which are a lot to get Strontium's head around as he just learned about the light wave.


I should have avoided the issue, or written "which is not easily or noticeably affected by an external magnetic field"

kelseymh2 years ago

You wrote, "my question is that why can't the electric and magnetic components of light interact with matter." They do, all the time. You just don't notice, for several reasons. First, the size of the electric and magnetic fields in a light wave are incredibly tiny -- much, much, much, MUCH smaller than any electric or magnetic field you've ever dealt with -- so you don't notice things like magnetic attraction or electric "zaps." Second, the frequency of oscillation of light waves is millions of billions of times per second, and your sensory apparatus can only notice things at a few tens of times per second. Third, natural light isn't polarized -- the electric and magnetic fields are rather randomly oriented, so there is no net effect in any particular direction.

If you use a sufficiently intense beam (let's say, a few megawatts) of microwaves, then you can accelerate electrons to very high energies. That acceleration is done specifically by the electric field of the microwaves. Look up "linear accelerator" in Wikipedia to learn all of the details of how this works.

Light does interact with external magnetic fields. If you start with polarized light, passing through a magnetic field (either a strong field, or a very, *very* long distance of a weak field), the plane of polarization is rotated. Look up "Faraday effect" in Wikipedia to learn all the details of how this works.

The direction of the electric field in a polarized light wave is defined as the direction of polarization. That's because polarizing materials (like the plastic in your sunglasses) are sensitive to the electric field, and only allow waves to pass if the field is aligned _along_ their long molecules, not across them. Look up "Polarizer" in Wikipedia to learn all the details of how this works.