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Answers to Readers' Questions on Physical Science:

EM Waves

The following 81 comments and questions have been sent in. They are listed according to date.

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Does the human body emit electromagnetic waves?

Question

June 15, 2010

This is really helpful! I have a question; does human body emit electromagnetic waves?

srishtee - India

19911

Answer

The nerves in the body work through electrical impulses, that in turn give off very weak electromagnetic waves of long wavelengths. There are devices that measure the human heart and brain waves that pick up those waves.

Also, the warmth of the body gives off infrared radiation, which are also electromagnetic waves.

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What is the function of electromagnetic waves?

Question

May 9, 2010

what is the function of electromagnetic waves?

okta - Indonesia

19691

Answer

Radio waves, television waves, microwaves, visible light, ultraviolet and x-rays are all forms of electromagnetic waves.

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Why does wavelength matter in transmission of waves?

Question

May 3, 2010

I have been studying electromagnetic waves for a while now and i have been very confused about how the length of the wave matters to what objects it can pass through?

Alex - UK

19661

Answer

While sound waves are compression waves, electromagnetic waves are transverse, similar the water waves, except in all directions.

Consider a water wave approaching a barrier that was less than the height of the wave. This would hinder the wave from passing the barrier. That is a good analogy or model of why electromagnetic waves are blocked by the separation of atoms in a material.

Another factor is that some materials have a crystalline structure that allows the waves to pass through. Very long waves, such as radio waves, simply go around everything.

There is no pat answer, because there are so many variables involved, but this should give you somewhat of an answer to your question.

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Can you change the wavelength?

Question

April 22, 2010

Is it possible to convert a particular electromagnetic wave to another wave in the electromagnetic spectrum. for example, convert visible light wave to microwave, or infrared to microwave.

How is this possible.

thank you for your response

Michaels - Sweden

19585

Answer

Using the Doppler effect, you can increase or decrease the wavelength according to the relative motion and direction of the source. However, the velocity must be fairly great to cause a significant change in wavelength.

For the equations, see:
http://www.school-for-champions.com/science/light_doppler_equations.htm

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Electromagnetic waves in a rainbow

Question

February 24, 2010

If in rainbow em waves are used? What is use of em waves in mobile?

Ashish - India

19280

Answer

The electromagnetic spectrum runs from long wavelength radio and mobile phone waves to visible waves to short wavelength x-rays. The rainbow consists of waves in the visible part of the spectrum. Each color has its own wavelength.

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What does an electromagnetic wave consist of?

Question

February 15, 2010

what does an electromagnetic wave consist of?

Supreet - India

19221

Answer

It is a vibration of the electrical and magnetic fields in space. Scientists are not sure if it is a property of space or if there is some other mechanism that carries these vibrations.

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Convert electromagnetic wave to electrical energy?

Question

February 6, 2010

Is it posssible to convert an em wave to electrical energy?
how to increase the strength of em wave?

dinesh - India

19167

Answer

Photocells convert visible electromagnetic waves into electricity. Similar devices convert other forms of electromagnetic waves into electricity.

Amplitude is the intensity of the wave. The wavelength determines its energy.

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What type of wave is an ultrasonic wave?

Question

December 10, 2009

Which part of the electromagnetic spectrum does the Ultrasonic wave falls into?

NASIR - India

18818

Answer

An ultrasonic wave is a high-frequency sound wave. The word "sonic" denotes it is a sound wave.

The electromagnetic spectrum relates to radio waves, visible light waves, x-rays, and other such waves

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Ultrasonic waves and electromagnetic spectrum

Question

November 1, 2009

Which part of the electromagnetic spectrum does the Ultrasonic wave falls into?

biswajit - India

18605

Answer

Ultrasonic is a high frequency sound wave ("sonic" = sound). It is not part of the electromagnetic spectrum.

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Is there a EMF device to check freshness of fruits?

Question

July 28, 2009

1) Is there a EMF device to check freshness of fruits and vegetables?

2) Can EMF apply to testing physical condition?

Quan - USA

18073

Answer

There is a device that used a small electrical current to measure freshness of foods, called EFresh. See:
http://www.ipgdx.com/EFresh-Measures-Food-Freshness.html

Usually, people are concerned about EMF radiation causing harm to them. I don't know of any EMF devices that can measure the physical condition of a person.

Microwaves are sometimes used to measure physical faults in structures.

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