Home > 科學?魔法? > 重溫物理
23 Mar

重溫物理

Posted by 13 comments

小時候上課都沒有聽課(即使有聽課大概也聽不懂,因為老師也是一知半解而已),現在後悔了,現在來重溫一點物理。主要是因為日本福島核子危機談到這些的緣故。

核子彈
核子彈有兩種。一種是核裂變(nuclear fission),另一種是核聚變(nuclear fusion)。原子彈(atomic bomb)是基於核裂變原理製造的。氫彈(hydrogen bomb)則是基於核聚變。

核聚變
就是將兩個原子核以強大的能量融合在一起。融合的過程中會釋放出更大的能量。由於需要很強大的能量,核聚變須使用核裂變為導火線。核聚變能釋放出比核裂變更大的能量,也相對的比較少放射線污染。

核裂變
就是將外來中子逼進原子核,使其不穩定而分裂。分裂的過程會釋放出大能量、兩個不穩定的原子核、及游離中子。不穩定的原子核則會釋放出放射線。游離中子又會去撞擊另一個原子核,產生另一個分裂。這樣的過程以幾何速度重複著,就是所謂的連鎖效應(chain reaction)。

放射性衰變(radioactive decay)
不穩定性的原子會衰變成為穩定性的原子。衰變的過程中會釋放出能量,即放射線。不同性質的原子擁有不同釋放的機率。

半衰期(half-life period)
原子釋放出一半能量的機率。根據測不准定理,單一原子的釋放期是不可預測的,但是整體統計上(幾兆兆。。兆粒原子)還是可以預測的。『半衰期三百年』就是三百年後這些原子的能量為目前的一半。

放射線(radiation)
其實就是波長極短的光。可見光的波長約為 400 ~ 700 納米。彩虹有紅橙黃綠藍靛紫,七種色,紅外線比可見光長,紫外線比可見光短。X 射線比紫外線短。大約是 0.1 納米。伽馬射線的波長是最短的,約為 0.00001 納米。

伽馬射線(gamma ray)
由於伽馬射線的波長極短,穿透力強,它可以破壞細胞。舉個例子,刀鋒很銳(波長短)的刀比刀鋒鈍(波長長)的刀更能割穿你的皮膚。

Categories: 科學?魔法?
Tags:
  1. drkhtang
    April 4th, 2011 at 13:27 | #1

    @ktang
    最重要是,沒有心。

  2. ktang
    April 4th, 2011 at 13:19 | #2

    @drkhtang
    没冷气没音乐没啥的,那敢叫你喔。。。?

  3. drkhtang
    April 3rd, 2011 at 11:14 | #3

    @ktang
    講降大聲。自己躲起來喝酒也沒有叫我。

  4. drkhtang
    April 3rd, 2011 at 11:13 | #4

    @AKH
    1. I presume this is not a question?

    2. In the nuclear fusion process, only heavier isotopes of Hydrogen are used, i.e. 2H an 3H, or Hydrogen with 2 neutrons and 3 neutrons. When forcing 2H and 3H together, the result is Helium-4, i.e. Helium isotopes of 2 protons and 2 neutrons. The remaining one neutron is freed, and the binding energy is released.

    4. Frequency is proportional to power. Think about your PC processor clock. The higher it is, the more power it consumes. Ray (a collection of light particles) generally gets weaker as per the inverse square law, as it disperses over distance, the number of light particles occupying the same dimension decreases. The energy of the particle itself, no it does not decrease over distance. Otherwise our universe would have been in total darkness today.

    6. No. Fusing atoms heavier than iron does not release energy, instead it absorbs energy. That’s why the fission process is used for Uranium, which is heavier than iron.

  5. AKH
    April 2nd, 2011 at 13:30 | #5

    @ktang
    Hh neither the questions nor the answers are important; i just testing myself whether still have a curious mind to ask & learn …..
    Ok, will drop by ur ophis next week then 🙂

  6. ktang
    April 2nd, 2011 at 12:58 | #6

    两个雄来我噢非斯小酢,答案就出来嘹。

  7. AKH
    April 1st, 2011 at 23:38 | #7

    1. Lighter atom? e.g. Hydrogen, H with 1 proton & 1 neutron? so “(strong or weak?) nuclear force” is weaker. By applying enough force to bring H close together you can fuse them together. Force also means pressure, the huge pressure require can be achieved by applying very very high temperature (like surface of sun?).
    2. If you fuse two H together it become He with 2 proton & 2 neutron? in the process what ‘mass’ is being converted to energy?
    4. Compare different types of rays (X, gamma, etc), each emit by 1 sub-atomic particle which is more powerful? Does the power of ray weaker over distance? What is the relationship of Ray frequency, power & distance?
    6. For heavier atom, e.g. Iron the force require to fuse them maybe is so gigantic that not possible to produce on earth. Even this force is possible with gigantic star at cosmo level, maybe before the atom can fuse the gravity will be already so strong that the star will collapse into a black hole.

    @drkhtang

  8. drkhtang
    March 30th, 2011 at 12:15 | #8

    @AKH
    Haha! Not too sure if I meet your criteria, but the questions you through out have already been asked and studied by myself via Google and Wikipedia some time ago. Let’s see if my memory serve me well..

    1. Short answer: hydrogen is lighter and requires less force to fuse together. Long answer: the stars in the universe are formed by the same fusion process, and this also explains why the third and fourth generation stars/planets do not fuse – because the gravitational force is insufficient to compress and fuse the heavier atoms that form these stars/planets.

    2. Short answer: hydrogen will be fused to become helium. Long answer: according to Einstain’s famous equation E=mc2, large amount of energy will be released during this fusion process. This is the basis of hydrogen bomb.

    3. Short answer: X-ray – thin. Gamma ray – thick. Long answer: it depends on the radiation power as well. With high radiation power, even X-ray can panetrate a lead wall as thick as ten’s of millimetres.

    4. Short answer: yes. Long answer: what do you mean by “more powerful”? Increasing the amplitude or increasing the frequency? The highest frequency detected in the universe is 10^27 Hz but it is not the highest theoretical frequency, which is Planck’s frequency of 10^43 Hz. Anyway I am not too confident about the figures.

    5. Yes. Don’t know.

    6. See answer to (1).

  9. AKH
    March 29th, 2011 at 19:10 | #9

    @AKH
    Typo error: ‘Fission’ in the questions should be ‘Fusion’

  10. AKH
    March 29th, 2011 at 19:07 | #10

    Fission chain reaction is usually triggered by neutron released by radioactive element hitting another atom usually at the end of periodic table. This atom (e.g.Uranium 235/8?) is bulky & will breakdown/decay into smaller element, lost mass in the process and release huge energy follow Einstein’s E=mc2 formula.
    Questions:
    1. Why Fission normally occur to the element at the beginning of periodic table? e.g. Hydrogen
    2. What happen to hydrogen during the process?
    3. What is the thickness of lead wall require to block X-ray & gamma ray?
    4. Any more powerful ray than above 2? cosmic ray, neutron ray?
    5. Astronaut outside the rocket is exposed to all kind of radiation/rays? What is the main material in their space suite that can protect them?
    6. Can Fission happen to the element at the middle of periodic table? e.g. iron. aluminium

    Challenge: Try answer above without googling … just think or guess 😉

  11. drkhtang
    March 24th, 2011 at 10:30 | #11

    一點都不明顯 =_=

  12. shiam
    March 24th, 2011 at 07:53 | #12

    很明顯的,loctor極懊悔沒能成為物理學家。

  13. anak
    March 24th, 2011 at 00:42 | #13

    很明顯的… 這個議題太難懂……

  1. No trackbacks yet.