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what is perfect black body radiator?
Assalam -o- Aleikum Everyone,

I think that one needs to manage his or her time as well as their expenses, so i made a little effort for myself and hope that everyone finds it useful.

I've made the files on MS excel pls view it and comment on it.

thnx
allah hafiz
Ooh excel brother! :smile:
.S.O.S.
Would anyone here know whether a perfect black body radiator actually exists in reality? or its just an ideal model?

read on some website that theres no such thing, but im not sure i can trust it....


I vaguely remember reading that it doesn't in my astrophysics notes... I might be wrong though... Man, you're tempting me to go read again! :biggrin: Physics was cool but also hard! :p:
The Green Manalishi
I vaguely remember reading that it doesn't in my astrophysics notes... I might be wrong though... Man, you're tempting me to go read again! :biggrin: Physics was cool but also hard! :p:


:ditto:

From what I remember the closest thing to a prefect black body was graphite where about 2-3% of the incoming radiation was emitted, everything else was absorbed…That was the approximate model of an ideal black body and it wasn't prefect.

I think…
Yup... excel!!! i think thats the only software which might b useful for such stuff. Do u know any other?
The Green Manalishi
Ok two issues i wanted to raise up...

1.) We had a discussion yesterday and we heard some people wondering who'll protect/ provide for them if they don't get an education or something like that. I want to remind each and every one of you that there's a major shirk and a minor shirk and watch both. Allah (swt) provides - our yaqeen (sp?) is in Him.

If you'd like a practical example - Hajar, wife of Ibrahim (AS) but of course that's exceptional... But we look to the stories of the prophets (pbut) for examples and so on...

Humble warning to everyone, myself included and at the forefront of that.
Of course we need to take appropriate worldly precautions also like getting an education and making an effort and so on...

2.) Nationalism - our allegiance is with muslim around the world, regardless of demographics and skin colour, ethinicity and race etc. The Qur'an doesn't talk about Pakistan and the UK, it talks about believers and disbelievers.


JazakAllah Khair for that heads-up.
mizfissy815
:ditto:

From what I remember the closest thing to a prefect black body was graphite where about 2-3% of the incoming radiation was emitted, everything else was absorbed…That was the approximate model of an ideal black body and it wasn't prefect.

I think…


2-3% thats small! I thought it would be much greater than that, since a perfect black body is ment to absorb and re-emit all energy wavelengths.
.S.O.S.
2-3% thats small! I thought it would be much greater than that, since a perfect black body is ment to absorb and re-emit all energy wavelengths.


Ok…I'm clearly no physics master and I'm a little confused. What I described was an (almost) prefect black body absorber! Although technically it should be an (almost) perfect radiator too…laws of thermodynamics…I think.
In order for a black body to be a perfect radiator it must also be able to absorb all incoming radiation, thus being a perfect absorber as well. I remember it also depended on the temperature of the black body. But seeing as there is no perfect absorber, I think it's safe to assume there is no perfect radiator?

This stuff is way over my head… You had better post your question on the Physics forum, you'll probably get better (and more than likely correct) answers for your question.
:eek:
lil one
:eek:

What?
These people are geniuses
lil one
These people are geniuses

Some of them are very smart MashaAllah! :eek:
:yawn:
Farah fwded this to me.. I'm not bothered to take out all the >s :p: She has a cool name - 'Al-Kasaby'. What does it mean?

>Dung Pham gives Safia Al-Kasaby, right, a manicure at Modern Nails in Town
>'N Country as a preview of World Trade Center is shown on TV. Since
>converting to Islam, she has felt the stares that her hijab brings. [Times
>photos: Chris Zuppa]
>
>Her mother named her Elizabeth
after the queen of England. More than four
>decades later, she took another name: Safia Al-Kasaby, reflecting her new
>identity as a Muslima.
>
>Safia, 43, is an unlikely candidate for conversion. She claims Jewish and
>Puerto Rican ancestry. She is a former sergeant first class in the Air Force
>National Guard. And she lost eight relatives - one uncle and seven cousins -
>in the Sept. 11 terrorist attacks on the World Trade Center.
>
>Back then, Safia did not imagine the faith professed by the hijackers would
>one day become her own.
>
>"It didn't really matter who did it," says the Tampa woman now, reflecting
>on the 2001 attacks. "I just never hated Islam. I never hated Muslims. For
>me to be angry about what happened to the twin towers would be like me
>hating all the Germans that killed the
Jews."
>
>Safia embraced Islam last year, coming to the faith at a time when it is
>seemingly maligned anew with each new report of terror plots, wars in far
>away lands and dead American soldiers.
>
>Like other Muslims, Safia feels the tension all around her: curious stares
>because she wears the hijab or head scarf and store clerks who ask for extra
>identification.
>
>Just last month , officials at the U.S. Embassy in Cairo turned down an
>initial request from Safia's Egyptian fiance for a temporary visa. Safia was
>certain bigotry played a role.
>
>Her new faith also has widened the chasm among her Christian family. Her
>mother, three sisters and one of her daughters question her choice.
>
>Safia presses on.
>
>"For her to accept Islam, making that decision especially in
this day and
>time, it says you're ready to step up and deal with the challenges of this
>journey," said Pat "Aliyah" Cruse, a fellow Muslima and 11-year convert.
>
>Muslim Demographics in the USA
>
>Some demographers consider Islam to be the fastest-growing religion in the
>world. Of the 1.3-billion Muslims worldwide, 4.7-million live in the United
>States, according to the Association of Religion Data Archives.
>
>One of the world's oldest religions, Islam has been in the United States for
>generations. But the terrorist attacks on Sept. 11, 2001, thrust the
>religion and its adherents into the spotlight. Before the attacks, American
>Muslims largely kept to themselves. Now, many feel the public expects them
>to answer for the actions of those who commit heinous acts in the name of
>their
faith.
>
>Across the country, some Muslims complain of stereotyping, racial profiling
>and discrimination. Others pine for the days when Islam was rarely mentioned
>in headlines. Most dare not complain openly, religious and civic leaders
>say, for fear of being labeled unpatriotic or sympathetic to extremists.
>
>"There's a certain sense of indignation to being treated the way they've
>been treated," said Imam Mahdi Bray, executive director of the Muslim
>American Society's Freedom Foundation in Washington, D.C. "There's a kind of
>rage. The challenge is to make that a healthy rage."
>
>Many American Muslims say extremists misrepresent their faith. But
>convincing the public to separate Islam from terrorism at times seems an
>insurmountable hurdle.
>
>Opinion polls back up what American
Muslims say they feel every day: Masses
>of the U.S. populace view them negatively. In a USA Today/Gallup poll
>released in August , 39 percent of Americans said they feel prejudiced
>toward Muslims. Nearly one quarter of Americans polled said they would not
>want a Muslim as a neighbor.
>
>Another 39 percent want Muslims to carry special identification at all times
>and undergo enhanced security checks when boarding airplanes.
>
>Anti-Muslim sentiment also has popped up in the Tampa Bay area, home to an
>estimated 45,000 Muslims. In 2002, federal agents arrested a Seminole
>podiatrist, Dr. Robert Goldstein, on charges of plotting to blow up a
>mosque.
>
>Fearing for their wives' safety after Sept. 11, husbands of immigrant Muslim
>women pulled them out of leadership roles in Islamic women's groups.
Fathers
>encouraged daughters to remove their hijabs in public to avoid harassment.
>Muslim women complained of verbal abuse in retail stores. One woman's hijab
>was ripped from her head by a customer in her husband's store.
>
>Children get few passes. Last spring , athletic officials benched Temple
>Terrace's Briana Canty when she refused to remove her head scarf in an
>amateur youth basketball league tournament. Rather than recognize Islamic
>holidays, the Hillsborough County School Board voted to rescind all
>religious holidays, a move it later reversed.
>
>This is the new reality for American Muslims. Advances are often eclipsed by
>setbacks.
>
>Quoting Charles Dickens, Ihsan Bagby, a leading Muslim demographer and
>associate professor of Islamic Studies at the University of Kentucky,
said
>this is the best and worst of times for Muslims in America.
>
>"This frustration, this pressure will ultimately produce positive results as
>Muslims continue to strive to become full members of this society," Bagby
>said. "Overall, everybody will look back at this period, they'll see this
>possibly as a turning point in the history of Islam in America."
>
>Challenges for American Muslims
>
>Despite challenges for Muslims, Islam continues to grow, buoyed by births
>and new converts such as Safia.
>
>Raised by her grandparents in Puerto Rico, Safia grew up in a home of melded
>cultures and faiths. Her grandfather was a Jew, who fled Germany during the
>Holocaust. Her grandmother was Catholic. Safia ultimately chose Judaism, a
>faith she believed was her birthright.
>
>But
Judaism eventually let her down, Safia said. In 1997, nearly destitute,
>she approached a North Tampa synagogue for help. Officials at the shul
>wanted to know if she was a member. She was not. They asked her if she was
>really Jewish.
>
>"They said just because I had a relative along the line didn't make me
>Jewish," said Safia. "That was the first wall. That I wasn't pure."
>
>Battling rejection, Safia left the synagogue. For eight years, she did not
>participate in organized religion.
>
>She found Islam in 2005 on the third day of a Moroccan vacation.
>
>"I just felt like God was there," she said, recalling her visit to a mosque
>during the call for prayer. "I said, 'This is it. I believe there is only
>one God. His name is Allah, and his messenger is Mohammed.'"
>
>At first, Safia's
family didn't take her seriously. And some colleagues at
>her banking job looked askance at her new Moroccan-inspired Islamic attire.
>Safia quickly toned it down, wearing scarfs only around her neck. She dared
>not pray at work.
>
>Mostly, Safia kept her new faith at home, learning about her religion on Web
>sites and Islamic chat rooms.
>
>Safia went to the Islamic Society of Tampa Bay Area in June and asked for
>the imam. She wanted to renew her shahadah, the formal declaration of the
>Islamic Creed. Safia also was out of work. The imam gave her a job managing
>the society's office. The group also stocked her refrigerator and paid her
>rent and electricity bill.
>
>At last, Safia said, she had found a spiritual family. It helps blunt the
>sting of the rejection from her biological
one.
>
>Safia's eldest daughter, Sylvia, wants little to do with her. A Baptist and
>young military widow, Sylvia berated Safia when she showed up at her
>husband's funeral wearing a hijab and carrying a Koran.
>
>At home in Town 'N Country, Safia raises two daughters. Ten-year-old Natalia
>says her mother's religion is cool.
>
>Ada, 18, appreciates Safia's transformation and doesn't put up with people
>who make fun of Islam or stereotype Muslims.
>
>"I say, 'Wait a minute. My mom's a Muslim,'" Ada said. "She's not a
>terrorist."
>
>Safia hopes the world will see her as an example of what Islam really is.
>Still early in her conversion, she is a Muslima in transition.
>
>She studies the Koran and prays five times a day. She also wears makeup and
>has French-manicured acrylic
nails. Sometimes she covers and sometimes -
>when she fears heckling or worse - she does not.
>
>There are victories: Her fiance received his visa and the two married
>Friday.
>
>She looks forward to the day when her religion is not an issue.
>
>"I don't want to have whispers behind me, whispers in front of me," she
>said. "I want to be able to blend in, keep my faith and blend in."
>
>
>
>Times researcher Cathy Wos contributed to this report. Sherri Day can be
>reached at [email protected] or 813-226-3405.
mizfissy815
Ok…I'm clearly no physics master and I'm a little confused. What I described was an (almost) prefect black body absorber! Although technically it should be an (almost) perfect radiator too…laws of thermodynamics…I think.
In order for a black body to be a perfect radiator it must also be able to absorb all incoming radiation, thus being a perfect absorber as well. I remember it also depended on the temperature of the black body. But seeing as there is no perfect absorber, I think it's safe to assume there is no perfect radiator?

This stuff is way over my head… You had better post your question on the Physics forum, you'll probably get better (and more than likely correct) answers for your question.


I found out from physics forums, that Cosmic Microwave Background (CMB, that static you hear on radios is like 1% of that) is near enough perfect black body...because it had so long (since the start of the universe) to come to thermal equilibrium.

If you wanted to know.
lil one
These people are geniuses


^And thats the girl that got 5A* and 5As talking :smile:
.S.O.S.
I found out from physics forums, that Cosmic Microwave Background (CMB, that static you hear on radios is like 1% of that) is near enough perfect black body...because it had so long (since the start of the universe) to come to thermal equilibrium.

If you wanted to know.

I know what CMB radiation is and read something with correlation between the two topics - CMB radiation and black body emittors but i wasn't sure of that...
basically at the start of the universe...(with the big bang) about 10^(to the power of)-36 seconds after the BB, the universe was very hot you had electrons, neutrons and protons all free!! lol moving about

then about 10^-31 (i think) seconds the nuclei formed, but because the electrons were still free, they were abosorbing any photons of light and other radiation (that why astronomers can't see before this time or at this time, into the big
bang singularity, because the light was absorbed, no light comming out
)
so its an absorber there

then the electrons condensed to the neutral atoms...and relased energies in terms of photons of light and radiation and thus behaving as a radiator
^ that was about 400,000 years (i think this is as far as astronomers can see into the past, they can't see anything before, after 400,000 years of BB) after the BB.
and that radiation is the CMB radiation its cooled to about 2.9...K or 2.8...K, that's it equilibrium temperature i guess.

^ i learnt all that at uni....i should have guessed the universe would be like a black body.
but since the universe is said to be expanding...shouldn't that value be decreasing? hmmm

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