Naked Science Forum
General Science => General Science => Topic started by: adamg on 30/06/2006 03:09:29
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Here are some more fascinating questions. I provide answers in 27 hours.
1. Although the meter was originally defined as 1/10,000,000th of 1/4th the circumfrence of the earth at the equator, it is today defined, officially, as the wavelength of Krytpon-86 radiation. True or False?
2. Saturn's density is so low that it would float in a pool of water, assuming one could find one large enough. True or False?
3. While AM radio waves can be as short as 10 Meters, FM radio waves can be as long as 193-580 Meters. True or False?
Adam Andrew Galas
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quote:
Originally posted by adamg
Here are some more fascinating questions. I provide answers in 27 hours.
1.Although the meter was originally defined as 1/10,000,000th of 1/4th the circumfrence of the earth at the equator, it is today defined, officially, as the wavelength of Krytpon-86 radiation. True or False?
It would be true if they had managed to measure the circumference of the Earth correctly.
quote:
2. Saturn's density is so low that it would float in a pool of water, assuming one could find one large enough. True or False?
I had to look it up, and to my surprise, it is true.
quote:
3. While AM radio waves can be as short as 10 Meters, FM radio waves can be as long as 193-580 Meters. True or False?
FM and AM refer to modulation, not to wavelength. Either modulation can be applied to any wavelength or frequency (as can phase modulation, and various other modulation types).
George
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The website I am looking at claims that wavelength is different between the two. This is not a trick question. Here's a hint, it has something to do with the distance AM waves can travel at night.
Adam Andrew Galas
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The metere is now defined in terms of the wavelength of light The krypton line is one that is usually favoured for accuracy.
Saturn is less dense than water but its atmosphere is very deep that's why it's so light.
The final question is ambiguous
Agree with another someone about the precise details of AM and FM you CAN uuse AM and FM modulations on any frequencies amateur radio usesrs sometimes use FM on short wave bands but they normally use SSB SC (single sideband suppressed carrier) modulation which is the most power efficient modulation scheme.
Normal FM radios usually receive 88 -108 MHz which is around three metres
193-580 meteres is around the limits of the normal medium wave AM radio band short wave radio goes down to 30Mhz or 10metres.
Learn, create, test and tell
evolution rules in all things
God says so!
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quote:
Originally posted by adamg
The website I am looking at claims that wavelength is different between the two. This is not a trick question. Here's a hint, it has something to do with the distance AM waves can travel at night.
The the site is plain wrong.
I agree that most modern consumer radio receivers are marked as AM and FM to designate what used to be called MW and VHF. If you had used the old terms, MW and VHF, then your statement is correct. Most modern commercial transmissions in the MW band are Amplitude Modulated; and most transmissions in the VHF band are Frequency Modulated, but there is no physical requirement that it be so, these are merely the standards the industry have used (there are technical reasons for that preference, but it is still a preference and not a requirement).
George
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I suppose the site was referring to amplitude due to the topic at hand, (how AM signals can bounce off the ionosphere for hundreds of kilometers at night).
I should have specified amplitude, for that I apologize. However, in terms of the competition, that shall remain the question. In the future I shall endevour to be as specific as possible.
Adam Andrew Galas
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Here are the answers.
1. Although a meter used to defined as 1/10,000,000th of 1/4th the circumfrence of the earth at the equator, it was changed in 1960 to the wavelength of radiation from Krypton-86.
But in 1983 it was changed to the distance light travels in 1/299,792, 458 of a second.
So the answer to number one is FALSE.
2. True, Saturn is the least dense planet in the solar system.
3. I apologize if the wording of this question was ambiguous. The answer is FALSE. AM radio waves have the longer wavelengths, FM the shorter.
Adam Andrew Galas
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In the first answer you havent specified how you have defined the second. This is also defined in terms of a spectral line. I am not quite sure but I think it is the Cesium standard at the moment. I intimated this in my first reply to this question.
Learn, create, test and tell
evolution rules in all things
God says so!
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Whether a signal is amplitude modulated or frequency modulated, will probably have very little effect on whether you can bounce it off the ionosphere, the important thing is what the frequency of the carrier wave is. If the frequency is in the Short Wave band, then depending on conditions it can bounce around the ionosphere very well. I don't think MW or LW are nearly as good at it, mostly they just diffract over the horizon slightly.
Basically the person who wrote the site was using the confusing convention on english radios (they do it properly in german) that FM means VHF and AM means LW,MW or SW.
-
quote:
Originally posted by adamg
Here are some more fascinating questions. I provide answers in 27 hours.
1.Although the meter was originally defined as 1/10,000,000th of 1/4th the circumfrence of the earth at the equator, it is today defined, officially, as the wavelength of Krytpon-86 radiation. True or False?
It would be true if they had managed to measure the circumference of the Earth correctly.
quote:
2. Saturn's density is so low that it would float in a pool of water, assuming one could find one large enough. True or False?
I had to look it up, and to my surprise, it is true.
quote:
3. While AM radio waves can be as short as 10 Meters, FM radio waves can be as long as 193-580 Meters. True or False?
FM and AM refer to modulation, not to wavelength. Either modulation can be applied to any wavelength or frequency (as can phase modulation, and various other modulation types).
George
-
The website I am looking at claims that wavelength is different between the two. This is not a trick question. Here's a hint, it has something to do with the distance AM waves can travel at night.
Adam Andrew Galas
-
The metere is now defined in terms of the wavelength of light The krypton line is one that is usually favoured for accuracy.
Saturn is less dense than water but its atmosphere is very deep that's why it's so light.
The final question is ambiguous
Agree with another someone about the precise details of AM and FM you CAN uuse AM and FM modulations on any frequencies amateur radio usesrs sometimes use FM on short wave bands but they normally use SSB SC (single sideband suppressed carrier) modulation which is the most power efficient modulation scheme.
Normal FM radios usually receive 88 -108 MHz which is around three metres
193-580 meteres is around the limits of the normal medium wave AM radio band short wave radio goes down to 30Mhz or 10metres.
Learn, create, test and tell
evolution rules in all things
God says so!
-
quote:
Originally posted by adamg
The website I am looking at claims that wavelength is different between the two. This is not a trick question. Here's a hint, it has something to do with the distance AM waves can travel at night.
The the site is plain wrong.
I agree that most modern consumer radio receivers are marked as AM and FM to designate what used to be called MW and VHF. If you had used the old terms, MW and VHF, then your statement is correct. Most modern commercial transmissions in the MW band are Amplitude Modulated; and most transmissions in the VHF band are Frequency Modulated, but there is no physical requirement that it be so, these are merely the standards the industry have used (there are technical reasons for that preference, but it is still a preference and not a requirement).
George
-
I suppose the site was referring to amplitude due to the topic at hand, (how AM signals can bounce off the ionosphere for hundreds of kilometers at night).
I should have specified amplitude, for that I apologize. However, in terms of the competition, that shall remain the question. In the future I shall endevour to be as specific as possible.
Adam Andrew Galas
-
Here are the answers.
1. Although a meter used to defined as 1/10,000,000th of 1/4th the circumfrence of the earth at the equator, it was changed in 1960 to the wavelength of radiation from Krypton-86.
But in 1983 it was changed to the distance light travels in 1/299,792, 458 of a second.
So the answer to number one is FALSE.
2. True, Saturn is the least dense planet in the solar system.
3. I apologize if the wording of this question was ambiguous. The answer is FALSE. AM radio waves have the longer wavelengths, FM the shorter.
Adam Andrew Galas
-
In the first answer you havent specified how you have defined the second. This is also defined in terms of a spectral line. I am not quite sure but I think it is the Cesium standard at the moment. I intimated this in my first reply to this question.
Learn, create, test and tell
evolution rules in all things
God says so!
-
Whether a signal is amplitude modulated or frequency modulated, will probably have very little effect on whether you can bounce it off the ionosphere, the important thing is what the frequency of the carrier wave is. If the frequency is in the Short Wave band, then depending on conditions it can bounce around the ionosphere very well. I don't think MW or LW are nearly as good at it, mostly they just diffract over the horizon slightly.
Basically the person who wrote the site was using the confusing convention on english radios (they do it properly in german) that FM means VHF and AM means LW,MW or SW.