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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 next 10 letters




Visible Light Does light travel at different speeds in glass? India
EM Waves What is meant by chromatic source? India
EM Waves Are the ultrasonic waves electromagnetic waves? India
Infrared Radiation Emissivity and infrared radiation UAE
Dispersion of Light Dispersion of white light through a glass slab India
EM Waves Do all photons have the same energy? India
X-rays Which type of rays use for cut the metal? Pakistsn
Speed of Light My ideas on the speed of light USA
Refraction of Light Relativity and index of refraction Slovak Republik
Light Why is the sky blue? Pakistan

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First 10 letters

Does light travel at different speeds in glass?

Topic: Visible Light


November 25, 2011

light has different wavelenghth, is it true that different wavelengths travel with different speed in glass medium?

chirag - India



The different wavelengths or colors of light travel at slightly different speeds when going through a material like glass or water. For more about this, see: Refraction of Light.

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What is meant by chromatic source?

Topic: EM Waves


October 17, 2011

What is meant by chromatic source? Give example

Manivannan - India



A chromatic source is usually a musical sound progressing by semitones, especially to a tone having the same letter name, as in C to C sharp.

It can be used with light waves or certain frequencies, but the term is primarily used in music.

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Are the ultrasonic waves electromagnetic waves?

Topic: EM Waves


October 17, 2011

Are the ultrasonic waves electromagnetic waves? Give proper reason.

Manivannan - India



Ultrasonic are high frequency sound waves (sonic) created by a vibrating source. Electromagnetic waves are vibrations of electrical and magnetic fields. EM waves include light, radio and microwaves.

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Emissivity and infrared radiation

Topic: Infrared Radiation


September 17, 2011

I have 4 questions i'm confused about. Please answer thoroughly..

1) What factors affect how much infrared radiation an object absorbs?
2) Which surfaces will not absorb infrared radiation?
3) What factors affect how much infrared radiation an object emits?
4) How does temperature of an object affect the amount of infrared radiation it will emit?

This is very important, please help!

Sabeen - UAE



Black objects absorb infrared radiation much more than lighter colored objects. Rough surfaces absorb more than shiny surfaces.

The emissivity of a material is its ability to emit infrared radiation. A black object usually has the best emissivity. Also emissivity depends on temperature and wavelength. See What is Emissivity? for more information.

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Dispersion of white light through a glass slab

Topic: Dispersion of Light


September 12, 2011

why we don't get dispersion of white light when light is passed through glass slab??
(i want answer without double prism explaination)
i need a ray diagram of it to.

Mohamadali - India



In Refraction of Light, there is a diagram showing how a beam of light is refracted by a parallel slab of glass. Although the different wavelengths of light bend at different angles when going from air to glass, they bend at the same angle when going from glass to air. Thus the beam is parallel and you cannot see a separation of colors.

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Do all photons have the same energy?

Topic: EM Waves


August 19, 2011

All photones should have the same energy as it is the name for the minimum energy the quantum.sometimes it is heard of high energy photones. what does it mean?




A photon is an elementary particles that can be represented as both a particle and as a wave. You could think of a simple photon as a compressed wave-packet with a specific wavelength that corresponds to its energy.

Since this is a difficult concept, we normally think of electromagnetic energy as a waveform. The shorter the wavelength, the higher the frequency and the greater the energy. Energy = hf, where h is the Planck constant and f is the frequency.

However, the number of photons does not represent the energy of the wave. Instead the number of photons represents the brightness.

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Which type of rays use for cut the metal?

Topic: X-rays


August 9, 2011

which type of rays use for cut the metal?

usman - Pakistsn



Usually, a high powered CO2 laser is used to cut metals. The wavelength is in the infrared area. X-rays are typically not used.

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My ideas on the speed of light

Topic: Speed of Light


August 8, 2011

My ideas on the speed of light: The speed of light is relative to the force of gravity in which the light is traveling through. In a black hole the speed of light is zero, in space the speed of light is infinite. Light has only been measured on the planet Earth. What about on the Moon or Mars or in deep space? How can we be sure that the speed of light is 186,286 miles per second in deep space or in different gravity fields.

E. - USA



That is an interesting concept. However, if the speed of light in space was infinite, we would see events immediately after they happen. It takes light about 8 minutes to come from the Sun to the Earth.

Since gravitational force can bend a ray of light, it also can slow the light down. So, where the force was small, the speed of light would be the greatest.

One question then is: What is the speed of gravity? When an object in space moves, how long does it take for the new force arrive?

See: Gravitational Speed for more about that topic.

It is good that you are thinking of new ideas. That is how scientific discoveries are made.

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Relativity and index of refraction

Topic: Refraction of Light


July 25, 2011

Why relativity is written of the refractive index of light in a physical environment?

Jozef - Slovak Republik



The refractive index of light is simply the ratio of the speed of light in a vacuum divided by the speed of light in the material.

Typically, relativity does not come into play with the index of refraction equation. However, there are special cases where the index is less than 1, but that does not violate relativity.

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Why is the sky blue?

Topic: Light


July 8, 2011

why the sky is blue.

Altaf - Pakistan



The sky is blue because the blue wavelengths in the sunlight are scattered at an angle toward the Earth. When you look towards the sun at sunset, you will see more red and orange colors in the sky, because the blue light has been scattered away from the line of sight.

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