:)

Ahlan Wa Sahlan. Assalamu'alaikum

Sabtu, Oktober 06, 2012

Cerita Putri Salju-Bahasa inggris

SNOW WHITE



Once upon a time in mid winter, when the snowflakes were falling like feathers from heaven, a beautiful queen sat sewing at her window, which had a frame of black ebony wood. As she sewed, she looked up at the snow and pricked her finger with her needle.

Three drops of blood fell into the snow. The red on the white looked so beautiful, that she thought, “If only I had a child as white as snow, as red as blood, and as black as this frame.” Soon afterward she had a little daughter that was as white as snow, as red as blood, and as black as ebony wood, and therefore they called her Little Snow-White.

Now the queen was the most beautiful woman in all the land, and very proud of her beauty. She had a mirror, which she stood in front of every morning, and asked:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
And the mirror always said:
You, my queen, are fairest of all.
And then she knew for certain that no one in the world was more beautiful than she.

Now Snow-White grew up, and when she was seven years old, she was so beautiful, that she surpassed even the queen herself.

Now when the queen asked her mirror:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
The mirror said:
You, my queen, are fair; it is true.
But Little Snow-White is still
A thousand times fairer than you.

When the queen heard the mirror say this, she became pale with envy, and from that hour on, she hated Snow-White. Whenever she looked at her, she thought that Snow-White was to blame that she was no longer the most beautiful woman in the world. This turned her heart around. Her jealousy gave her no peace. Finally she summoned a huntsman and said to him, “Take Snow-White out into the woods to a remote spot, and stab her to death. As proof that she is dead bring her lungs and her liver back to me. I shall cook them with salt and eat them.”

The huntsman took Snow-White into the woods. When he took out his hunting knife to stab her, she began to cry, and begged fervently that he might spare her life, promising to run away into the woods and never return. The huntsman took pity on her because she was so beautiful, and he thought, “The wild animals will soon devour her anyway. I’m glad that I don’t have to kill her.” Just then a young boar came running by. He killed it, cut out its lungs and liver, and took them back to the queen as proof of Snow-White’s death. She cooked them with salt and ate them, supposing that she had eaten Snow-White’s lungs and liver.

Snow-White was now all alone in the great forest. She was terribly afraid, and began to run. She ran over sharp stones and through thorns the entire day. Finally, just as the sun was about to set, she came to a little house. The house belonged to seven dwarfs. They were working in a mine, and not at home. Snow-White went inside and found everything to be small, but neat and orderly. There was a little table with seven little plates, seven little spoons, seven little knives and forks, seven little mugs, and against the wall there were seven little beds, all freshly made.

Snow-White was hungry and thirsty, so she ate a few vegetables and a little bread from each little plate, and from each little glass she drank a drop of wine. Because she was so tired, she wanted to lie down and go to sleep. She tried each of the seven little beds, one after the other, but none felt right until she came to the seventh one, and she lay down in it and fell asleep.

When night came, the seven dwarfs returned home from the work. They lit their seven little candles, and saw that someone had been in their house.

The first one said, “Who has been sitting in my chair?”
The second one, “Who has been eating from my plate?”
The third one, “Who has been eating my bread?”
The fourth one, “Who has been eating my vegetables?”
The fifth one, “Who has been sticking with my fork?”
The sixth one, “Who has been cutting with my knife?”
The seventh one, “Who has been drinking from my mug?”
Then the first one said, “Who stepped on my bed?”
The second one, “And someone has been lying in my bed.”
And so forth until the seventh one, and when he looked at his bed, he found Snow-White lying there, fast asleep. The seven dwarfs all came running, and they cried out with amazement. They fetched their seven candles and looked at Snow-White. “Good heaven! Good heaven!” they cried. “She is so beautiful!” They liked her very much. They did not wake her up, but let her lie there in the bed. The seventh dwarf had to sleep with his companions, one hour with each one, and then the night was done.

When Snow-White woke up, they asked her who she was and how she had found her way to their house. She told them how her mother had tried to kill her, how the huntsman had spared her life, how she had run the entire day, finally coming to their house. The dwarfs pitied her and said, “If you will keep house for us, and cook, sew, make beds, wash, and knit, and keep everything clean and orderly, then you can stay here, and you’ll have everything that you want. We come home in the evening, and supper must be ready by then, but we spend the days digging for gold in the mine. You will be alone then. Watch out for the queen, and do not let anyone in.”

The queen thought that she was again the most beautiful woman in the land, and the next morning she stepped before the mirror and asked:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
The mirror answered once again:
You, my queen, are fair; it is true.
But Little Snow-White beyond the seven mountains
Is a thousand times fairer than you.

It startled the queen to hear this, and she knew that she had been deceived, that the huntsman had not killed Snow-White. Because only the seven dwarfs lived in the seven mountains, she knew at once that they must have rescued her. She began to plan immediately how she might kill her, because she would have no peace until the mirror once again said that she was the most beautiful woman in the land. At last she thought of something to do. She disguised herself as an old peddler woman and colored her face, so that no one would recognize her, and went to the dwarf’s house. Knocking on the door she called out, “Open up. Open up. I’m the old peddler woman with good wares for sale.”
Snow-White peered out the window, “What do you have?”
“Bodice laces, dear child,” said the old woman, and held one up. It was braided from yellow, red, and blue silk. “Would you like this one?”
“Oh, yes,” said Snow-White, thinking, “I can let the old woman come in. She means well.” She unbolted the door and bargained for the bodice laces.
“You are not laced up properly,” said the old woman. “Come here, I’ll do it better.” Snow-White stood before her, and she took hold of the laces and pulled them so tight that Snow-White could not breathe, and she fell down as if she were dead. Then the old woman was satisfied, and she went away.

Nightfall soon came, and the seven dwarfs returned home. They were horrified to find their dear Snow-White lying on the ground as if she were dead. They lifted her up and saw that she was laced up too tightly. They cut the bodice laces in two, and then she could breathe, and she came back to life. “It must have been the queen who tried to kill you,” they said. “Take care and do not let anyone in again.”

The queen asked her mirror:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
The mirror answered once again:
You, my queen, are fair; it is true.
But Little Snow-White with the seven dwarfs
Is a thousand times fairer than you.

She was so horrified that the blood all ran to her heart, because she knew that Snow-White had come back to life. Then for an entire day and a night she planned how she might catch her. She made a poisoned comb, disguised herself differently, and went out again. She knocked on the door, but Snow-White called out, “I am not allowed to let anyone in.”
Then she pulled out the comb, and when Snow-White saw how it glistened, and noted that the woman was a complete stranger, she opened the door, and bought the comb from her. “Come, let me comb your hair,” said the peddler woman. She had barely stuck the comb into Snow-White’s hair, before the girl fell down and was dead. “That will keep you lying there,” said the queen. And she went home with a light heart.
The dwarfs came home just in time. They saw what had happened and pulled the poisoned comb from her hair. Snow-White opened her eyes and came back to life. She promised the dwarfs not to let anyone in again.

The queen stepped before her mirror:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
The mirror answered:
You, my queen, are fair; it is true.
But Little Snow-White with the seven dwarfs
Is a thousand times fairer than you.

When the queen heard this, she shook and trembled with anger, “Snow-White will die, if it costs me my life!” Then she went into her most secret room — no one else was allowed inside — and she made a poisoned, poisoned apple. From the outside it was red and beautiful, and anyone who saw it would want it. Then she disguised herself as a peasant woman, went to the dwarfs’ house and knocked on the door.
Snow-White peeped out and said, “I’m not allowed to let anyone in. The dwarfs have forbidden it most severely.”
“If you don’t want to, I can’t force you,” said the peasant woman. “I am selling these apples, and I will give you one to taste.”
“No, I can’t accept anything. The dwarfs don’t want me to.”
“If you are afraid, then I will cut the apple in two and eat half of it. Here, you eat the half with the beautiful red cheek!” Now the apple had been so artfully made that only the red half was poisoned. When Snow-White saw that the peasant woman was eating part of the apple, her desire for it grew stronger, so she finally let the woman hand her the other half through the window. She bit into it, but she barely had the bite in her mouth when she fell to the ground dead.

The queen was happy, went home, and asked her mirror:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
And it answered:
You, my queen, are fairest of all.
“Now I’ll have some peace,” she said, “because once again I’m the most beautiful woman in the land. Snow-White will remain dead this time.”

That evening the dwarfs returned home from the mines. Snow-White was lying on the floor, and she was dead. They loosened her laces and looked in her hair for something poisonous, but nothing helped. They could not bring her back to life. They laid her on a bier, and all seven sat next to her and cried and cried for three days. They were going to bury her, but they saw that she remained fresh. She did not look at all like a dead person, and she still had beautiful red cheeks. They had a glass coffin made for her, and laid her inside, so that she could be seen easily. They wrote her name and her ancestry on it in gold letters, and one of them always stayed at home and kept watch over her.

Snow-White lay there in the coffin a long, long time, and she did not decay. She was still as white as snow and as red as blood, and if she had been able to open her eyes, they still would have been as black as ebony wood. She lay there as if she were asleep.

One day a young prince came to the dwarfs’ house and wanted shelter for the night. When he came into their parlor and saw Snow-White lying there in a glass coffin, illuminated so beautifully by seven little candles, he could not get enough of her beauty. He read the golden inscription and saw that she was the daughter of a king. He asked the dwarfs to sell him the coffin with the dead Snow-White, but they would not do this for any amount of gold. Then he asked them to give her to him, for he could not live without being able to see her, and he would keep her, and honor her as his most cherished thing on earth. Then the dwarfs took pity on him and gave him the coffin.

The prince had it carried to his castle, and had it placed in a room where he sat by it the whole day, never taking his eyes from it. Whenever he had to go out and was unable to see Snow-White, he became sad. And he could not eat a bite, unless the coffin was standing next to him. Now the servants who always had to carry the coffin to and fro became angry about this. One time one of them opened the coffin, lifted Snow-White upright, and said, “We are plagued the whole day long, just because of such a dead girl,” and he hit her in the back with his hand. Then the terrible piece of apple that she had bitten off came out of her throat, and Snow-White came back to life.

She walked up to the prince, who was beside himself with joy to see his beloved Snow-White alive. They sat down together at the table and ate with joy.
Their wedding was set for the next day, and Snow-White’s godless mother was invited as well. That morning she stepped before the mirror and said:
Mirror, mirror, on the wall,
Who in this land is fairest of all?
The mirror answered:
You, my queen, are fair; it is true.
But the young queen
Is a thousand times fairer than you.

She was horrified to hear this, and so overtaken with fear that she could not say anything. Still, her jealousy drove her to go to the wedding and see the young queen. When she arrived she saw that it was Snow-White. Then they put a pair of iron shoes into the fire until they glowed, and she had to put them on and dance in them. Her feet were terribly burned, and she could not stop until she had danced herself to death.

Selasa, September 25, 2012

Difraksi Sinar X


DIFRAKSI SINAR-X PADA KRISTAL

 

Sejarah mengenai difraksi sinar-x telah berjalan hampir satu abad ketika tulisan ini disusun. Tahun 1912 adalah awal dari studi intensif mengenai difraksi sinar-x.  Dimulai  dari  pertanyaan M. van Laue kepada salah  seorang  kandidat doktor P.P.  Ewald  yang  dibimbing  A.Sommerfeld,  W.  Friedrich  (asisten  riset Sommerfeld) menawarkan dilakukannya eksperimen mengenai 'difraksi sinar-x'. Pada  saat  itu  eksperimen  mengenai  hamburan  sinar-x  sudah  dilakukan  oleh Barkla.

 

Laue   mengawali   pekerjaannya   dengan   menuliskan   hasil   pemikiran teoretiknya dengan mengacu pada hasil eksperimen Barkla. Laue berargumentasi, ketika sinar-x melewati sebuah kristal, atom-atom pada kristal bertindak sebagai sumber-sumber  gelombang  sekunder,  layaknya  garis-garis  pada  geritan  optik (optical grating). Efek-efek difraksi bisa jadi menjadi lebih rumit karena atom- atom tersebut membentuk  pola tiga dimensi. Eksperimen  difraksi sinar-x yang pertama  dilakukan  oleh  Herren  Friedrich  dan  Knipping  menggunakan  kristal tembaga  sulfat  dan  berhasil   memberikan   hasil  pola  difraksi  pertama  yang kemudian  menjadi  induk  perkembangan  difraksi  sinar-x  selanjutnya  Difraksi sinar-x merupakan proses hamburan sinar-x oleh bahan kristal.

 

Pembahasan  mengenai  difraksi   sinar-x  mencakup   pengetahuan   yang berhubungan dengan hal-hal berikut ini:

1. pembentukan sinar-x

2. hamburan (scattering) gelombang elektromagnetik

3. sifat kekristalan bahan (kristalografi)

 

Dengan  demikian,  difraksi  sinar-x  adalah  topik  lanjut  di  bidang  fisika  yang memerlukan pengetahuan dasar yang cukup banyak dan komplek.

 

Sinar X

 

1.     Merupakan radiasi elektromagnetik berenergi tinggi

2.    Dihasilkan akibat interaksi antara berkas berkas elektron eksternal dengan elektron pada kulit atom.

3.    Spektrum sinar x memiliki:

a.   panjang gelombang antara10-5-1 nm,

b.  frekuensi antara 1017-1020 Hz,

c.   Energi antara 103-106 eV.

d.  Panjang gelombnag Sinar X memiliki orde yang sama dengan jarak antara atom.

 

http://ladyo.files.wordpress.com/2008/04/sinar-x.jpg?w=400&h=253

Munculnya sinar X  karena adanya perubahan energi kinetik yang dihentikan

 

 

 

 

 

 anoda menjadi cahaya ( gelombang elektromagnetik )

 

 

 

 

 

 

Prinsip difraksi Sinar X

 

1.     Sinar X terpancar dari tabung Sinar X.

2.    Difraksi sinar X yang konvergen diterima slit.

3.    Sinar X diterima detektor,

4.    diubah menjadi sinyal listrik.

5.    Sinyal ini dihitung sebagai analisa pulsa tinggi.

 

Difraksi Sinar X

1.     Proses hamburan sinar X oleh bahan kristal.

2.    Difraksi tergantung pada struktur kristal dan panjang gelombang.

a.   jika (λ) ukuran atom, tidak terjadi difraksi

b.  jika (λ) < ukuran atom, terjadi difraksi

3.    Teknik yang digunakan dalam karakterisasi material.

4.    Untuk mendapatkan informasi mengenai ukuran atom.

 

 

 

Hukum Bragg

Jika seberkas sinar-X mengenai bidang-bidang Kristal tersebut maka sinar akan berhamburan ke segala arah. Karena keteraturan susunan atom-atom pada arah tertentu, gelombang hamburan sinar-X akan mengalami interfrensi konstrutif. Sedangkan pada arah yang lain, gelombang hamburan sinar-X akan mengalami interferensi destruktif.

 

Contoh Soal

Kristal dengan jarak antar bidang (d) = 2Ǻ, Ka dari logam tembaga. Energi = 8 kev, berapa sudutnya?

 

Jawab

E =  ch

        l

 

      (8x103) (1,602x10-19)  =  (6,6 10-34)  (3x108)

                                                        l

 

       l = 1,5449 x 10-10 m

       λ = 1,54 Ǻ

       2d sin θ  =  nλ

       Sin θ = 2,2

       θ  = 22,64

Interaksi Sinar X dengan Material

 

Ada dua proses yang terjadi bila seberkas sinar-x ditembakkan ke sebuah atom, yaitu:

1.     Energi berkas sinar-x terserap oleh atom, atau

2.    sinar-x dihamburkan oleh atom.

 

Dalam   proses   yang   pertama,   berkas   sinar-x   terserap   atom   melalui   Efek Fotolistrik  yang  mengakibatkan   tereksitasinya  atom  dan/atau  terlemparnya  elektron- elektron dari atom. Atom akan kembali ke keadaan dasarnya  dengan (1) memancarkan elektron (melalui  Auger  effect), atau (2) memancarkan  sinar-x  floresen  yang memiliki panjang  gelombang  karakteristik  atom  tereksitasinya.  Pada  proses  yang  kedua,  ada bagian berkas yang mengalami hamburan  tanpa kehilangan  kehilangan  energi (panjang gelombangnya tetap) dan ada bagian yang terhambur dengan kehilangan sebagian energi (Hamburan Compton).

 

Jadi serapan total sinar-x terjadi karena efek fotolistrik dan hamburan Compton. Namun, hamburan  Compton   memiliki efek menyeluruh  yang dapat diabaikan,  kecuali untuk radiasi dengan panjang gelombang  pendek yang mengenai  material dengan berat atom rendah.

 

Dalam  interaksinya  dengan  material,  sinar-x  juga dapat  mengalami  polarisasi linier  (seperti  halnya  cahaya  tampak),  baik  parsial  maupun  total.  Dengan  demikian berkas  sinar-x  terpolarisasi  dapat  diperoleh  dengan  cara  hamburan  dan  untuk  sudut hamburan   90°,   polarisasi   lengkap   terjadi,   yaitu   komponen   vektor   medan   listrik tegaklurus bidang yang dibentuk berkas datang dan berkas terhambur.

 

Berkas hamburan sinar-x oleh material yang dapat diukur adalah intensitas. Intensitas berkas sinar-x yang mendekati paralel adalah fluks energi yang melewati satu satuan  luasan  tertentu  per  satuan  waktu.  Untuk  gelombang   planar  monokromatik, intensitas sebanding dengan kuadrat amplitudo getaran. Intensitas radiasi yang dihasilkan oleh  sumber  titik  (atau  sumber  kuasi-titik)  pada  arah  tertentu  adalah  energi  yang dipancarkan per detik per satuan sudut ruang pada arah itu. Dalam pengukuran intensitas mutlak, cara termudah adalah dengan menentukan jumlah foton teremisi atau tertangkap (detektor) per satuan waktu, bisa per satuan luas atau per satuan sudut ruang.