Luminosity?????
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jwc
Posted:
Mon Mar 05, 2007 6:05 am
Joined: 05 Mar 2007
Posts: 2
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Hi Guys what an awesome site. I Love astromony and got lots to learn. I hope you guys don't mind my questions because I have alot of them, here goes...
1) Is luminisity the amount of light arriving at a location or is it the amount of light leaving a source?
2.)What would be the frequency of an electromagnetic wave having a wave length equal to Earth's diameter?
3.) how would I figure out the wavelength of a 100-MHz radio signal?
4.)If object A has a temperature of 5000K and object B has temperature of 10,000 K wouldn't object B produce 16X more flux?
5.) If A wave x meters long has a speed of y meters per second How do I find out the frequency of the wave? Would it be x/y?
Thanks so much!!!
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Lydia
Site Admin
Posted:
Wed Mar 07, 2007 12:37 pm
Joined: 03 Feb 2004
Posts: 597
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Answers to your questions
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Hi there: I asked a smart friend your questions and here's what he said:
1) Is luminosity the amount of light arriving at a location or is it
the amount of light leaving a source?
AMOUNT OF LIGHT LEAVING THE SOURCE
2.)What would be the frequency of an electromagnetic wave having a wave length equal to Earth's diameter?
APPROX 23.25 cycles/sec
3.) how would I figure out the wavelength of a 100-MHz radio signal?
FORMULA = WAVELENGTH X FREQUENCY = SPEED OF LIGHT, c=hf
4.)If object A has a temperature of 5000K and object B has temperature
of 10,000 K wouldn't object B produce 16X more flux?
YES, LUMINOSITY IS PROPORTIONAL TO THE TEMPERATURE RAISED TO THE 4th POWER
5.) If A wave x meters long has a speed of y meters per second How do I
find out the frequency of the wave? Would it be x/y?
USE FORMULA ABOVE
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jwc
Posted:
Wed Mar 07, 2007 3:03 pm
Joined: 05 Mar 2007
Posts: 2
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Hi There,
Thanks so much for your help I really do appreciate it. I have a few more questions if you don't mind.
1.) What would be the frequency of a electromagnetic wave having a wavelength equal to the earth's diameter(in meters)?And did you figure that out?
2.)The blackbody emission spectrum of object A peaks in the UV region of the EM spectrum, at a wavelength of 200nm. That of object B peaks in the red region, at 650 nm. According to Wien's law how many times hoter than B is A? And did you figure that out?
3.)What is the wavelength of a 100-Mhz radio signal? In meters and how do you get that?
4.) A train of waves is moving at a speed of 30 m/s. The frequency of the waves is 10 Hz. What is the wavelength? Is it 300m?
Thank you I appreciate your help. Have a great day and once again thanks.
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Lydia
Site Admin
Posted:
Fri Mar 09, 2007 1:50 pm
Joined: 03 Feb 2004
Posts: 597
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Ok- Just so you know... I didn't know the answers to your questions.
I asked a friend who is a " really smart person"  ... and who knows about these things.
I am sure he will happily answer your next questions as well, since it benefits everyone to know this.
Excellent questions, BTW.
LL
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Lydia
Site Admin
Posted:
Thu Mar 15, 2007 11:12 am
Joined: 03 Feb 2004
Posts: 597
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Answers (from that " really smart person" )
1) 23.25. I'm assuming the Earth's diameter is 8,000 miles.
2) 200nM corresponds to T = 14,490 K
650 nm corresponds to T = 4458 K
Both temperatures are in degrees Kelvin.
Weins displacement law: Wavelength max = 0.2898/T
The energy flux is proportional to T raised to the 4th power. So the
200nM
has 3.25 times the energy flux than the 650 nM object.
3) 100Mhz radio signal is 865,238 meters.
4) wavelength is 3 meters. use the formula c = hf, where c = velocity
of
object, h - wavelength, f - frequency
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