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Feedback Comments on Electromagnetic Waves

by Ron Kurtus

A total of 311 comments and questions have been sent in. They are listed according to date.

You can read them to further your understanding of the subject.

List of most recent 10 letters




X-rays How do x-ray machines improve security? Canada
Light Identify factors in dispersion of light Guyana
Dispersion of Light Which has the greatest wavelength? Nigeria
Lasers Could a powerful laser destroy an asteroid? UK
EM Waves Safe range for EMF from electronic equipment India
EM Waves Using a very strong electromagnetic wave to move things USA
EM Waves Sensitive to electrical waves USA
EM Waves How much radiation comes from PC monitor? UK
Infrared Radiation Regular versus infrared heating pads India
Infrared Radiation Oxygen and nitrogen absorb IR Australia

Next 10

How do x-ray machines improve security?

Topic: X-rays


April 17, 2016

how do x-ray machines improve the security in our society? and could you explain how.


Irraj - Canada



X-ray machines are used in airports and public buildings to screen luggage and packages and make sure there are no guns or other weapons hidden inside. The view of the item will show an outline of the gun, since the x-rays don't go through the metal easily.

In this way, troublemakers can be stopped before entering. This improves the security. But note that other devices must be used to detect some explosives that don't show up with an x-ray.

See X-rays and Need for Security for more information.

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Identify factors in dispersion of light

Topic: Light


July 9, 2012

HI, im doing a school based assessment and im asked to identify the variables/factors in the dispersion of light. Can you help me with that?

Cassandra - Guyana



Refer to our lesson Dispersion of Light

The variables or factors in dispersion of light are color or wavelength, index of diffraction, and the incoming angle, and shape of the dispersing object.

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Which has the greatest wavelength?

Topic: Dispersion of Light


June 11, 2012

in dispersion of white light, which has the greatest wave lenght? 2. Explain doppler effect

pascal uzo - Nigeria



Red has a longer wavelength than the other colors. Blue has the shortest wavelength.

Also see Doppler Effect for Waveforms for information on that subject.

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Could a powerful laser destroy an asteroid?

Topic: Lasers


June 6, 2012

Hi i was just wondering if laser could be used on a much larger scale as a mobile earth defense gun against asteroids hitting earth in 2029 or 2036 Apothis could it work & could it be powerful enough.Thanks Andy.

Andrew - UK



The Ballistic Missile Defense Program has powerful CO2 lasers that can destroy an incoming missile. But the strength would not be near enough to put a dent in an asteroid.

Even a nuclear bomb would not destroy an asteroid, because of their size. However, the plan is to use nuclear bombs to deflect the path of the asteroid enough so that it would miss the Earth.

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Safe range for EMF from electronic equipment

Topic: EM Waves


June 2, 2012

what is the maximum range of electro magnetic radiation emitted from a electronic equipment while it is working

Ranjith - India



Much depends on the type of equipment and the shielding it has. A good article on the subject is Electro Magnetic Field (EMF) - Hazardous to Our Health?

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Using a very strong electromagnetic wave to move things

Topic: EM Waves


April 5, 2012

Is it possible for an object to produce a very strong electromagnetic wave with a long wavelength and be able to attach itself to the wave magnetically and same frequency? Thus, be able to ride the wave, like a surfer rides an ocean wave? Not the same as an object able to ride along an electromagnetic field, eg; bullet train.

Brian - USA



AC electricity at 50Hz or 60Hz produces a very long electromagnetic wave that can affect and move electrons over a great distance. However, the strength or amplitude required to move even a small object would be extremely difficult--if not impossible--to achieve.

A bullet train uses magnetic fields to achieve two goals. First, it holds the train above the track. Then by changing the polarities of the various electromagnets along the track in a waveform, it moves the vehicle forward.

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Sensitive to electrical waves

Topic: EM Waves


April 1, 2012

I feel I am magnetically charged to the microwave, computer, electric outlets, and when I am under a light source I feel it in my head. I feel a burning sensation in my back or legs and If I have any metal on me, it hurts where the metal is. I've read about electromagnetic weapons, and that's exactly what I feel is happening to me. I am loosing the hair on my head. When I wear my glasses I feel stange sensations. My heart has palipatations, my mouth is swollen where my partial denture is and I feel my body is deteriorating and it cracks and aches all over. Please Help.

Theresa - USA



Several things may be happening.

Some people are very sensitive to static electricity, such that they attract it and actually get electrically charged. In such people, they also often get electrical shocks when touching metal objects.

Another group of people are hypersensitive to electromagnetic frequencies (EMF). It sound more like that is what you have. See EMF Sensitivity for a list of symptoms.

Also see EMF and Health

I hope this helps. Best wishes on good health.

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How much radiation comes from PC monitor?

Topic: EM Waves


February 29, 2012


I came across your site while trying to discover what the height is of the electromagnetic waves that are being emitted from my personal computer. However, I don't seem to be able to find the answer - well, at least, not in language that I can understand.

I don't suppose you can help? Any answers would be very much appreciated.


Paul - UK



The radiation from your computer is called Extremely Low Frequency (ELF) radiation. It is also emitted from power lines, electrical sub-stations, TVs and other electrical and electronic appliances. The field strength is about 3-6 milligauss. However, that number is meaningless to most of us.

Old televisions and computer monitors gave off a fair amount of radiation. But now, they are highly controlled, such that the danger is minimal. LCD monitors give off almost zero radiation.

See the US FDA article on Radiation-Emitting Products for more information.

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Regular versus infrared heating pads

Topic: Infrared Radiation


February 29, 2012

The information given is very informative.

Regarding the heating pads
I have come across the people selling normal heating pad.
and Infrared heating pads.
can you diferentiate between the two?
Some people highlihts infrared heating pads for various advantages over the normal heating pad ! are these claim fake ?

From this article I have understood that any heating pad when heated gives of infrared heat.
then what is the infrared heating pad ? are these special?
Please guide

r - India



A normal heating pad uses heated electrical wires or heated liquid that reaches the skin by moving through the material by conduction. Although they do give off some infrared, most of the heat transfer is by conduction.

An infrared heating pad shines the radiation on your skin, thus heating the tissues. The claim is that the radiation will go deeper into the tissue and thus heat it more effectively, while a standard heating pad primarily only heats the surface and does not penetrate as rapidly.

Besides heating further into the tissue, the infrared heating pads operate at a lower temperature, preventing possible burns or drying of the skin.

If it is a high-quality heating pad, the infrared version sounds like a good concept.

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Oxygen and nitrogen absorb IR

Topic: Infrared Radiation


December 11, 2011

I understand that, whilst oxygen and nitrogen absorb and radiate primarily in the UV and visible range, there are some bands in IR.

Could these IR bands have any effect (a) absorbing and/or (b) emitting at atmospheric temperatures?

Do oxygen and nitrogen radiate enough spontaneously to cool or do they first transfer energy to GHG molecules which then do the radiating?

Could the total absorption of IR in the atmosphere by O2 and N2 (if any) possibly be comparable with the total absorbed by CO2.

Doug - Australia



Yes, the IR absorption bands of Oxygen and Nitrogen affect the greenhouse effect.

Some references on this are: Near-infrared absorption spectroscopy of oxygen and nitrogen gas mixtures - (abstract), Greenhouse effect, and Visualizing the Greenhouse Effect – Molecules and Photons.

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