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Politeknik Kesehatan Jakarta 2

Jalan Hang Jebat 3 Jakarta Selatan .

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Minggu, 06 Oktober 2013

explanation


Why is snow the color white?

Water in the pure form is colorless. If there are any impurities present, the color of the water changes. Snow also can take the color of other objects. For example, in the case of glaciers deep inside the ice block it appears blue in color. But, snow is slightly different from the ice. Snow is the collection of ice crystals that are tiny and attached to one another. The ice crystal is also clear and colorless while the accumulated crystals combine to form snowflakes.
The snow is visible to us due to the presence of light. Snow falls from the above in the atmosphere and reaches the ground. The ice crystals will enable the light falling on them to get reflected on their surface. There are multiple faces for the crystals and hence the light also gets scattered. Visible light has various wavelengths of light that are visualized by us. When light falls on any object some part of the light will be absorbed and the other part will get reflected. The reflected part of light reaches our eyes and makes us to recognize the colors.
The light fallen on the ice crystals also do not pass through the crystals for long distance but tend to change directions. The light also gets reflected at an angle inthe interior of the ice. As snow exists as collection of several snowflakes on theground, the light that falls on them will not have a particular wavelength that is reflected with some regularity. So, most of the light that falls on the snow will almost completely gets reflected back. The light that gets reflected by the snow will remain white most of the time as the total light and not any one wavelength of it is reflected back. Hence, snow is white in color.

Why is Arizona so hot?


Arizona is called by some people as Arid Zona. Arizona is considered as a neighbor to the east side and is termed as sunburn state. It is so hot in Arizona that it is normally said that you can boil the egg on your leg. The heat in Arizona is a dry heat and it is not hot all through the year. It appears that it will be hot in Arizona till October and during the Christmas time it will be so cool that frost forms at that time. The Laguna Mountains in California tend to block the cool marine air that flow from the Pacific Ocean. The flow of air is inhibited to move eastwards to Yuma. These Mountains were known to keep the heat in them. The weather pattern in the summer makes the places like Utah, Nevada and Arizona to have high pressures. This high air pressures make the air in the North of Arizona to move at latitudes which are in height. Due to this reason a place called Yuma at Arizona which is situated at higher altitudes will be experiencing more heat and get almost baked.
The level of precipitation is very low at this place due to these Mountains. If any storm arises in the Pacific Ocean and moves towards California it moves from west to east direction. The clouds that are formed touch the Mountain and will be made forcibly to cool fast and condense further. The condensed clouds fall as rain on theMountains. So, the clouds that passes on to the Mountains will not allow raining in Arizona. The Southern part of Arizona is a desert and hence it is too hot in this region. In the Phoenix region, the month of June seems to be very hot and with less humidity. People in Arizona experience monsoon storms at the summer time.The summer in Arizona has higher humidity levels with the wind and dust storms occurring during the season. We can also observe desert rains at intervals.

Where does wind come from?


Chris Weiss, assistant professor of atmospheric science at Texas Tech University, explains.
Simply put, wind is the motion of air molecules. Two concepts are central to understanding what causes wind: air and air pressure. Air comprises molecules of nitrogen (about 78 percent by volume), oxygen (about 21 percent by volume), water vapor (between 1 and 4 percent by volume near the surface of the earth) and other trace elements. Every time we breathe, the air we inhale is composed of about the same relative ratios of these molecules, and a cubic inch of air at ground level contains about 1020 molecules.
All of these air molecules are moving about very quickly, colliding readily with each other and any objects at ground level. Air pressure is defined as the amount of force that these molecules impart on a given area. In general, the more air molecules present, the greater the air pressure. Wind, in turn, is driven by what is called the pressure gradient force. Changes in air pressure over a specified horizontal distance cause air molecules from the region of relatively high air pressure to rush toward the area of low pressure. Such horizontal pressure differences of all scales generate the wind we experience.
The areas of high and low pressure displayed on a weather map in large part drivethe (usually) gentle ambient wind flow we experience on a given day. Thepressure differences behind this wind are only about 1 percent of the total atmospheric pressure, and these changes occur over the range of multiple states.The winds in severe storms, in contrast, are a result of much larger and more concentrated areas of horizontal pressure change. Tornadoes are great examples. In June 2003 Tim Samaras of Applied Research Associates placed a scientific probe in the direct path of an F4 (devastating) tornado near Manchester, S. Dak. He found that the air pressure dropped by 10 percent of the total atmospheric value over the radius of the tornado. The magnitude of this air pressure change, and the very short distance over which it occurred, explains whythe winds are so destructive in this phenomenon: air molecules are very quickly accelerated into the very low pressure at the center of the tornado where thewater vapor contained in the air often condenses, creating the often visible “condensation funnel.”

Kamis, 03 Oktober 2013

hereditas

Materi Prinsip Hereditas - Biologi SMA Kelas XII Materi Prinsip Hereditas - SMA Kelas 12 1. Pewarisan sifat (karakter) dari induk (orang tua) kepada fillialnya melalui suatu perkawinan melibatkan gen (sebagai faktor pembawa sifat keturunan). 2. Mendel memilih kacang kapri untuk objek kajiannya, karena memiliki pasangan-pasangan yang kontras, melakukan autogami atau penyerbukan sendiri, mudah disilangkan, mampu menghasilkan keturunan banyak, dan cepat menghasilkan atau daur hidupnya pendek. 3. Hukum Mendel I disebut juga Hukum Segregasi, karena menyatakan bahwa pada waktu pembentukan gamet (meiosis), kromosom-kromosom homolognya memisahkan diri secara bebas. 4. Persilangan monohibrida adalah perkawinan dengan satu sifat (karakter) beda yang mencolok. 5. Genotip bersifat menurun dan diwariskan pada keturunan. 6. Fenotip adalah sifat yang tampak dari luar. Fenotip merupakan paduan dari genotip dengan lingkungannya. 7. Hukum Mendel II dikenal sebagai Hukum Asortasi atau Hukum Berpasangan Secara Bebas atau Hukum Penggabungan Bebas. 8. Persilangan dihibrida yaitu persilangan dengan dua sifat beda, dengan dua alel yang berbeda. 9. Back cross merupakan persilangan antara anakan F1 yang heterozigot dengan induknya yang homozigot dominan. 10. Test cross adalah menyilangkan suatu hasil persilangan dengan salah satu induk homozigot resesif. 11. Penyimpangan semu Hukum Mendel meliputi interaksi gen, kriptomeri, polimeri, epistasis-hipostasis, gen-gen komplementer, gen dominan rangkap, dan atavisme. 12. Kriptomeri yaitu gen dominan yang seolah-olah tersembunyi jika berdiri sendiri dan akan tampak pengaruhnya apabila bersama-sama dengan gen dominan yang lainnya. 13. Polimeri adalah pembastaran heterozigot dengan banyak sifat beda yang berdiri sendiri, tetapi memengaruhi bagian yang sama dari suatu organisme. 14. Sifat atau fenotip yang tadinya menghilang, dapat muncul kembali pada generasi berikutnya, melalui proses yang disebut atavisme. 15. Epistasis adalah faktor (gen) dominan yang menutupi gen dominan lain yang bukan alelnya, sehingga sifat yang dikendalikan gen yang tertutup tidak muncul. 16. Hipostasis adalah faktor (gen) yang tertutupi oleh gen dominan yang lain, yang bukan alelnya. 17. Peristiwa inheritansi baik pada hewan, tumbuhan, maupun manusia akan mengikuti pola-pola hereditas seperti adanya tautan, tautan seks, pindah silang, determinasi seks, adanya gen letal, dan non-disjunction. 18. Pindah silang dapat terjadi pada saat meiosis (pembentukan gamet). Pindah silang dapat berupa pindah silang tunggal atau pindah silang ganda. Untuk mengetahui kekuatan pindah silang dihitung nilai pindah silangnya (NPS). 19. Tipe-tipe determinasi seks meliputi tipe XY (pada lalat buah dan manusia), XO (belalang atau Ordo Orthoptera dan kepik atau Ordo Hemiptera), ZO (ayam dan itik), dan ZW (burung, serangga, dan kupu-kupu). 20. Gen letal dibedakan menjadi gen resesif letal (pada jagung albino) dan gen dominan letal (pada ayam redep dan tikus kuning). 21. Gagal berpisah atau non-disjunction dapat terjadi pada saat pembentukan gamet (meiosis). 22. Pewarisan sifat pada manusia dapat diturunkan melalui kromosom seks (kromosom X dan kromosom Y) atau kromosom autosom. 23. Sifat-sifat yang dapat diwariskan pada manusia meliputi jenis kelamin, kelainan menurun, golongan darah, dan ekspresi gen-gen yang dipengaruhi oleh seks. 24. Ada tiga macam sistem penggolongan darah, antara lain: sistem A, B, O; sistem MN, dan sistem Rhesus (Rh). 25. Kelainan menurun yang disebabkan oleh alel resesif dan dominan autosom adalah albino, gangguan mental, brakhidaktili, cystinuria, dan polidaktili. 26. Kelainan menurun yang disebabkan oleh alel resesif kromosom X adalah buta warna, anodontia, dan hemofilia. 27. Kelainan menurun yang disebabkan oleh alel resesif kromosom Y adalah Hypertrichosis, Hystrixgravier, dan Webtoes . 28. Pewarisan sifat pada manusia dapat dihindari melalui upaya perbaikan sosial meliputi upaya eugenetika dan eutenika. 29. Peta silsilah dapat menunjukkan keadaan atau sifat individu dalam keluarga besar (1 garis keturunan) sehingga dapat dilacak adanya individu