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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

Topic

Title

Country

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
 

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First 10 letters


What is infrared?

Topic: Infrared Radiation

Question

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

19474

Answer

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

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Questions about infrared radiation

Topic: Infrared Radiation

Question

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

19456

Answer

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.

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Relationship between frequency and wavelength of light

Topic: Dispersion of Light

Question

March 21, 2010

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

tilahun - Ethiopia

19403

Answer

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

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How much infrared is absorbed at noon?

Topic: Infrared Radiation

Question

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?

- USA

19367

Answer

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:
http://www.school-for-champions.com/science/infrared_greenhouse_effect.htm
for more information on it.

Your "climate change denial guy" is misinformed.

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Frequency and wavelength of light

Topic: Dispersion of Light

Question

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

19330

Answer

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.

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Electromagnetic waves in a rainbow

Topic: EM Waves

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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Phase shift on internal relfection

Topic: Light Snell's Law

Question

February 20, 2010

Hello,

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

19258

Answer

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.

See: http://www.physicsforums.com/showthread.php?t=112763

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How fast do x-rays travel?

Topic: X-rays

Question

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

19241

Answer

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

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What does an electromagnetic wave consist of?

Topic: EM Waves

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?

Topic: EM Waves

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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