List of Topics

SfC Home > Physics > Electromagnetic Waves >


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




Infrared Radiation What is infrared? India
Infrared Radiation Questions about infrared radiation Hong Kong
Dispersion of Light Relationship between frequency and wavelength of light Ethiopia
Infrared Radiation How much infrared is absorbed at noon? USA
Dispersion of Light Frequency and wavelength of light India
EM Waves Electromagnetic waves in a rainbow India
Light Snell's Law Phase shift on internal relfection USA
X-rays How fast do x-rays travel? India
EM Waves What does an electromagnetic wave consist of? India
EM Waves Convert electromagnetic wave to electrical energy? India

Next 10


First 10 letters

What is infrared?

Topic: Infrared Radiation


April 1, 2010

Wat is meant by infrared?

a.its passes one from to another object

b. its distance more than 1m to passes

c.infrared and bluetooth is same

alex - India



Infrared is light that is close to read and is similar to heat. Some of it can pass through glass.

Back to top

Questions about infrared radiation

Topic: Infrared Radiation


March 29, 2010

1. Why a filament light bulb will explode when water is shot on it?
2. All kinds of radiation are light(in terms of light)???
3. What is the meaning of good radiators?(actually, what are radiators?)
4. All objects can reflect and absorb radiation???(including the dull black surfaces???They can reflect light too????)
5. Why a larger object have a smaller surface area to volume ratio than a smaller object?
6. Objects on absolute zero(-273 degree celsius) also emit infra-red?

SORRY.I'm stupid.
I really want to get high marks on physics because I want to study physics the next year!
Please help me!

Kitty - Hong Kong



A light bulb can get very hot. When cold water is splashed on it, the different temperatures causes the glass to shatter so that the light bulb explodes.

Electromagnetic radiation covers a wide range of types of radiation, including x-rays, infrared radiation and visible light. To avoid confusion in the sciences, it is always good to say "visible light" instead of simply "light".

Some materials give off heat (infrared radiation) and even visible light more than other materials. They are called good radiators. Hot metals will radiate infrared much better than hot wood.

All objects reflect and absorb radiation, depending on the wavelengths of the electromagnetic radiation. Dull black surfaces are good absorbers of visible and infrared radiation, although they do reflect a tiny amount of radiation.

Objects at or near absolute zero will not emit infrared radiation, because there is not enough energy to do so.

Back to top

Relationship between frequency and wavelength of light

Topic: Dispersion of Light


March 21, 2010

what is the relation ship b/n frequency and wave length of light?

tilahun - Ethiopia



The speed of light equals frequency times wavelength: c = fw

Back to top

How much infrared is absorbed at noon?

Topic: Infrared Radiation


March 13, 2010

Help me with an argument?

I told someone that there are several ways to tell whether infrared is removed from the atmosphere more at sunset than at noon
-- hold your hand out
-- use a prism and thermometer

His answer is that most of the heat in sunlight is from the visible range being absorbed by the skin and warming it up, and that the atmosphere completely absorbs infrared so there is no difference in the amount of infrarad and the difference you feel between noon and sunset is only from the change in visible light -- that the infrared has all been absorbed by the atmosphere even at noon.

I'm an old guy, I've relied on NASA for this. He's a climate change denial guy certain that CO2 is completely blocking all the infrared in the atmosphere, so adding more CO2 won't change the climate, if that helps.

But my basic question is -- can your hand feel infrared, as distinct from heating from visible light?




The amount of infrared radiation at noon is slightly greater than at sunset, primarily because it passes through less atmosphere at noon. However, because the light at sunset is at a sharp angle, much more is reflected back into space. At noon, more radiation is absorbed by the ground and re-radiated as longer infrared.

Most of the infrared absorbed by the atmosphere is absorbed by water vapor in the air. Only around 18% is absorbed by CO2. This absorption increases the temperature of the atmosphere.

But increasing the percentage of CO2 and methane CH4 in the air will greatly increase the percentage of IR absorbed and thus increases the temp even more.

See: "Infrared, Gases and the Greenhouse Effect" at:
for more information on it.

Your "climate change denial guy" is misinformed.

Back to top

Frequency and wavelength of light

Topic: Dispersion of Light


March 5, 2010

Hi, I am scientist researching on astronomy and deep space. I would like to ask you following queries;

1) What is the role of frequency and wavelength in the propagation of light and sound waves?

2) If the frequency is kept constant, the change in wavelength will result in what observations of light/sound. Will it change colour?

3) If the wavelength is kept constant then the change of frequency will affect in the propogation of light/sound in what way? Will it change colour?

Baldevkrishan - India



Frequency times wavelength equals the speed of the waveform. However, sound does not travel in space, since matter is required for its propagation.

When light passes thought a material that changes its velocity, and its frequency is constant, the wavelength or color would change. The only way to change frequency is at the source of the sound or light.

Back to top

Electromagnetic waves in a rainbow

Topic: EM Waves


February 24, 2010

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

Ashish - India



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.

Back to top

Phase shift on internal relfection

Topic: Light Snell's Law


February 20, 2010


I still can't figure out the answer to this question; when light passes from a material with a high index of refraction into material with a low index of refraction, does some of the light reflect without a change of phase?

Sarah - USA



When light is reflected at the interface of low index to high, there is a 180 degree phase shift. At the interface of high index to low, there is no phase shift on reflection.


Back to top

How fast do x-rays travel?

Topic: X-rays


February 18, 2010

X-rays travel with the velocity of
A. light
B. sound
C. positive rays
D. alpha rays

give me the correct answer with explanation

vinod - India



X-rays are a form of electromagnetic radiation. All electromagnetic radiation travels at the speed of light.

Back to top

What does an electromagnetic wave consist of?

Topic: EM Waves


February 15, 2010

what does an electromagnetic wave consist of?

Supreet - India



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.

Back to top

Convert electromagnetic wave to electrical energy?

Topic: EM Waves


February 6, 2010

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

dinesh - India



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.

Back to top

Next 10


Hopefully, this reader feedback has helped provide information about Electromagnetic Waves issues.

Listen carefully

Resources and references

Ron Kurtus' Credentials


Electromagnetic Waves Resources


Top-rated books on Electromagnetic Waves

Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.

Feel free to establish a link from your website to pages in this site.

Where are you now?

School for Champions

Physics topics

Feedback on Electromagnetic Waves

Electromagnetic Wave topics

Short wavelengths

Visible frequencies

Longer wavelengths

Let's make the world a better place

Be the best that you can be.

Use your knowledge and skills to help others succeed.

Don't be wasteful; protect our environment.

You CAN influence the world.

Live Your Life as a Champion:

Take care of your health

Seek knowledge and gain skills

Do excellent work

Be valuable to others

Have utmost character

Be a Champion!

The School for Champions helps you become the type of person who can be called a Champion.