What is Alpha: Definition and 474 Discussions

Alpha (uppercase Α, lowercase α; Ancient Greek: ἄλφα, álpha, modern pronunciation álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , which is the West Semitic word for "ox". Letters that arose from alpha include the Latin letter A and the Cyrillic letter А.

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  1. jinn

    What is the Kinetic Energy of Alpha Particles Scattered by an Aluminum Plate?

    Homework Statement Onto an Aluminium 50μm thick plate, we send a beam of alpha particles with unknown kinetic energy. the cross section of the beam is 2cm2, density 1013 / scm2 . Whats the kinetic energy of the particles if every second we sense 105 scattered particles between the angles 40°...
  2. H

    B Current Flux from Alpha and Beta Radiation

    In a smoke detector there is 1 muCi of Am-241. I'm assuming that means it emits (3.7x10^10)*(1x10^-6)=3.7x10^4 alpha particles per second. Each alpha particle has a charge of 2e, so it seems to me that this stream of particles leaving the Am-241 pellet would carry a current of...
  3. KT KIM

    Trajectory of scattered alpha particle

    This is a famous experiment conducted by Rutherford, in this exprement, the alpha particle(+2e charge) repulsed from necleus by coulomb force, and eventually divert its trajectory by theta. I want to show the trajectory of alpha particle has asympotes which means it go out along that asympote...
  4. D

    What increases in nucleus as a result of alpha and beta decays

    Homework Statement Well one of the questions that I'm not too sure the answer to is what parameter in the nucleus increases as a result of alpha and beta decay.Homework EquationsThe Attempt at a Solution Not too sure, I mean atomic number decreases and so does mass number so. But what...
  5. I

    Alpha decay ##Q##-value, recoil energy, momentum

    Homework Statement Calculate the ##Q##-value for ##^{230}Th\to \; 226Ra + \alpha##. Also calculate the kinetic energy and the velocity of the daughter nuclei. Homework Equations Alpha decay ##Q = (m_X-m_X'-m_\alpha)c^2## Kinetic energy ##T_\alpha = \frac{Q}{1+\frac{m_\alpha}{m_{X'}}}##...
  6. J

    B Alpha is 1/137th of what? (Fine Structure Constant)

    Hi. With regard to the Fine Structure Constant, I have been trying to figure out the practical applications of the formula in nature but have had difficulty trying to discern what the 137 denominator in the equation represents. ie, it is 1 137th of what? Or, 137 whats? Is there a practical...
  7. Kara386

    Kinetic energy of alpha particle in alpha decay

    Homework Statement Consider the nuclear decay 21486Rn → 21084Po2- + α. Calculate the Q for this decay, and give the value of the kinetic energy of the alpha particle in the rest frame of the Rn nuclide. The rest mass of the Rn nuclide is 213.9954u, of Po is 209.9829u, of α is 4.00015u and of...
  8. F

    A Alpha Variation vs Cosmological Expansion: Basics Explained

    hello, My question will be quite naive for experts and reflects the fact that I'm new to the subject of varying the fine structure constant alpha and mainly need an introductory reference ... so if someone has a good one to advice ...thanks a lot i just don't understand the basics: how people...
  9. J

    What is heat-transfer coefficient alpha

    Hi everyone! I would like to confirm if heat-transfer coefficient α units in SI are W/m2 K. I have to use heat-transfer coefficient α in this formula: Heat-transfer resistance: 1/k = δ/λ + 1/α Where δ is material thickness and λ is thermal conductivity Thank you!
  10. H

    A mono-energetic alpha beam

    Hi, I calculated the scattered angle & the kinematic factors for both Al & Au to be Is what I did right? Also E (Alpha) = stopping power x depth = 250 x 0.5 = 125 keV As for the maximum & the minimum scattered energy i didn't know how?
  11. Titan97

    Thermal expansion of a rod with variable alpha

    Homework Statement The coefficient of linear expansion of a rod of length 1 meter (at 300K) varies with temperature as ##\alpha=\frac{1}{T}##, where T is the temperature. Find the increment in length when the rod is heated from 300K to 600K Homework Equations $$\Delta L=L\alpha \Delta T$$ The...
  12. F

    A double alpha disintegration?

    Hi everybody; I was watching footage from a cloud chamber and I stumbled upon a double alpha disintegration; both particles came from the same spot and their trajectory was shaped as a V; the only radioactive element which was in the air was the natural radon; after consulting the disintegration...
  13. Sergey_KGB

    A Po-210. Comparison of Gamma and Alpha spectrometry

    Hi Everybody! Just have read in the Report into the death of Alexander Litvinenko https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/493860/The-Litvinenko-Inquiry-H-C-695-web.pdf I'm very surpised to see that namely Gamma Spectrometry was used while only 1 in 100,000...
  14. M

    Finding Volumes of Sphere & Circular Cone: Alpha from 0 to Pi

    Use an appropriate volume integral to find an expression for the volume enclosed between a sphere of radius 1 centered on the origin and a circular cone of half-angle alpha with its vertex at the origin. Show that in the limits where alpha = 0 and alpha = pi that your expression gives the...
  15. B

    What properties do alpha helices and beta sheets impart to polypeptides?

    Still working on steric clashes of amino acid functional groups. Can anyone explain the properties that either the alpha helix or the beta sheet impart to a polypeptide. Ok, so they are configurations within a complex molecule that provide stability to the structure, but do they impart any...
  16. J

    Density Matrix and State Alpha

    There is something that I don't quite understand or want clarification. See John Wheeler article "100 years of the quantum" http://arxiv.org/pdf/quant-ph/0101077v1.pdf refer to page 6 with parts of the quotes read "so if we could measure whether the card was in the alpha or beta-states, we...
  17. Stephanus

    What Can You Do with Wolfram Alpha in Chemistry?

    Dear PF Forum, Do anybody know the 'Wolfram Alpha' for chemistry? For example. If I enter: HCl + NaOH The website will produce something like HCl + NaOH -> NaCl + H2O (+ or - energy would be preferable) or if I enter: C6H12O6 + O2 The website will produce something like: Do you mean: C6H12O6 +...
  18. P

    Distance of closest approach of alpha particle calc

    Homework Statement An alpha particle is accelerated from rest through a potential difference of 20kV. It travels directly towards a stationary Beryllium nucleus (4 protons, 5 neutrons). Calculate the distance of closest approach Homework EquationsThe Attempt at a Solution E=qv=(40x10^3)e...
  19. X

    Elastic collision between alpha particle and gold Nuclei

    Homework Statement When an alpha particle collides elastically with a nucleus, the nucleus recoils. Suppose a 3.94 MeV alpha particle has a head-on elastic collision with a gold nucleus that is initially at rest. What is the kinetic energy of (a) the recoiling nucleus and (b) the rebounding...
  20. 1

    Why we called the Helium particle as alpha particle?

    why we the alpha particle is taken as helium and beta as electron ? and what about gamma particle ? what is that? My 2nd question is that during alpha decay and beta decay there is decrease of 2 units in atomic number and one unit increase respectively ? what happen in gamma decay ?
  21. K

    How do I solve for the wavelength of an alpha particle?

    Homework Statement Compare 25-MeV alpha particles wavelengths with the size of a nucleon in a nucleus. Homework Equations λ = h/p E2 = p2c2 + m2c4 KE = ½mv2 p = mv The Attempt at a Solution To compare the wavelength of an α particle with a nucleon, I would need to divide the wavelength of...
  22. M

    Power produced from alpha decay

    Homework Statement Assume that a 14 kg sample of 240Pu is used to produce electrical power from its α decay. If your device is 60% efficient in producing electrical power, how much power can be produced? (in watts) Homework Equations Q=mass of plutonium-mass alpha-mass daughter; 240 plutonium=...
  23. Oribe Yasuna

    Alpha Particle & Gold Nucleus Collision

    Homework Statement An alpha particle (a helium nucleus, containing 2 protons and 2 neutrons) starts out with kinetic energy of 10.5 MeV (10.5x106 eV), and heads in the +x direction straight toward a gold nucleus (containing 79 protons and 118 neutrons). The particles are initially far apart...
  24. Oribe Yasuna

    Radius of a lead nucleus and alpha particle

    Homework Statement A lead nucleus contains 207 nucleons (82 protons and 125 neutrons) packed tightly against each other. A single nucleon (proton or neutron) has a radius of about 1 ✕ 10^−15 m. (a) Calculate the approximate radius of the lead nucleus. (b) Calculate the approximate radius of...
  25. N

    Electron Capture by alpha particle -- Frequency of photon?

    Homework Statement Electron with KE = 50eV is captured by Alpha particle, ie. HE++. Calculate the frequency of the emitted photon. Homework Equations KE = m/2 v^2; E=hf, En = Z^2*-13.6eV/n^2 The Attempt at a Solution Energy before = Energy after 50eV = 4*-13.6eV/1 + hf f = 1200nm
  26. J

    Copper K alpha lines, ionization potential, confused

    I'm a computer scientist who was recently given a book about quantum physics. I am confused about something in the book. Imagine shining an x-ray (produced by copper K alpha 1 emission) on an aluminium foil. I understand the basics of photoelectric effect. You shine the x-ray on target aluminium...
  27. N

    What Kind of Radiation Does the GM Counter Detect?

    Homework Statement There is a radioactive source plaed in front of the GM counter to predict the kind of radiation emmitted by the source. 1 : When the GM counter moves 5 cm away from the source, the count rate drops significantly. 2 : When a 5mm aluminium sheet is inserted...
  28. W

    What is the angle between coupled forces with a given moment and magnitude?

    Homework Statement The moment of the couple is 600k (N-m). What is the angle A? F = 100N located at (5,0)m and pointed in the positive x and positive y direction -F = 100N located at (0,4)m and pointed in the negative x and negative y direction Homework Equations M = rxF M = DThe Attempt at a...
  29. Jonski

    Reaction Force, find tension, a in the tangential, or alpha

    Homework Statement The diagram shows the instant when a long slender bar of mass 4.9 kg and length 4.9 m is horizontal. At this instant the mass m= 6.5 kg has a vertical velocity of 4.0 m/s. If the pulley has negligible mass and all friction effects may be ignored, what is the magnitude of the...
  30. G

    Calculation of alpha particles from 226-Ra decay

    I am trying to solve the following problem for my graduate course in isotope geochemistry. If 1 g of 226Ra is separated from its decay products and then placed in a vessel, how much helium (cm3) will accumulate in the vessel in 60 days? Here is what I know. The decay series from 226Ra to Lead...
  31. C

    Simulink vector space alpha beta transformation

    << Thread moved to the HH forums from the technical engineering forums, so no HH Template is shown >> The model: The goal: 1. Create a three phase voltage 2. Do a alpha-beta transformation 3. Do a Cartesian to Polar transformation 4 Check the output angle The expected result: Since the space...
  32. G

    Recoil of a hydrogen atom emitting Lyman alpha photon

    I am interested in what the recoil velocity of an initially stationary hydrogen atom in free space would be when it emits a Lyman alpha photon. I tried to do the calc and got about 3 metres per second which seems rather high.
  33. D

    Why does an alpha particle have 40mm range in air?

    Hey everyone... so I understand that an alpha particle, being a helium nucleus, is quite a large particle compared to, for example, a beta particle. Due to this, it will encounter a lot more collisions and impart its momentum to other particles of air at a much more rapid rate. Is there...
  34. abm77

    What is the speed at a great distance from the alpha particle

    Homework Statement An alpha particle has a charge of 2e and is fixed at the origin. A proton is located 2.00x10^-8 m from the alpha particle along the x-axis. When the proton is released, what is its speed at a great distance from the alpha particle q = 2e r = 2.00x10^-8 v = ? Homework...
  35. S

    Materials that are transparent to alpha particles?

    A mica window is used on Geiger counters. The thin mica is supposedly very transparent to alphas. But are there other materials? Extremely thin metal foils?
  36. mesa

    Needing elemental alpha particle scattering/peak resonances

    On our campus we have an ion beam analysis lab. It is used for compositional analysis through the firing of alpha particles at MeV energies at target samples (RBS). From here it is a simple matter of back scattering kinematics to calculate atomic masses thereby giving the general composition of...
  37. F

    Rate of Lyman Alpha photons emitted....

    First off, I'm not sure if this question should go here or in the homework section. It is an astronomy homework question BUT there are only physics subtopics and did not want to post it in the wrong section. Let me know if it should be moved to there! Homework Statement Consider a nebula...
  38. C

    Why is the central electrode in a G.M. tube positive?

    Why is the central electrode in a Geiger-Muller tube always positive (and not negative)? Many thanks!
  39. R

    Kinetic energy of alpha particle

    Homework Statement The kinetic energy (in keV) of the alpha particle, when the nucleus 84210Po at rest undergoes alpha decay, is A 5319 B 5422 C 5707 D 5818 Homework Equations ## E = mc^2 ## Kinetic energy ## = mv^2/2 ## The Attempt at a Solution alpha particle is emission of helium nucleus...
  40. patrickbotros

    Why doesn't an alpha particle have a +2 charge in alpha decay?

    The following equation is written in my book: 204Pb→4α + 200Hg If an alpha particle is a helium nucleus, why doesn't it have a +2 charge and why doesn't Hg have a -2 charge? Did my text just omit the charge?
  41. neilparker62

    Questions on the Lyman Alpha Profile

    A few questions about the solar Lyman Alpha profile as presented here. 1) This is from a 1978 study - are there more recent (higher resolution) profiles ? 2) The scale at the bottom is confusing - how does it relate to a wavelength scale ? 3) Where in the profile is the actual Lyman alpha line...
  42. R

    Why can't an alpha particle be captured by the nucleus?

    I understand that there are many attempts from inside the nucleus to tunnel out therefore if it was just one alpha particle trying to get in it wouldn't happen. I'm struggling with this derivation from class to describe the number of attempts: How does a velocity and size of the nucleus...
  43. Garlic

    Can Alpha Emitters Cause Nearby Gasses to Glow?

    Hello everyone, Can alpha emitters cause nearby (gasses or air) to be excited and glow like Radium or Tritium? Is there certain chemicals (maybe like phosphor) that are suitable for it?
  44. R

    Geiger counters and activity

    I'm doing high school physics and if a question says something like: A radioactive source gives count rate of 110 counts per second Can you say that the ACTIVITY is also 110 bq? My second question is how would a gieger counter detect gamma radiation? It is the least ionising of all three...
  45. D

    Tunneling with an alpha particle

    Homework Statement In a simple model for a radioactive nucleus, an alpha particle (m = 6.64×10^−27kg) is trapped by a square barrier that has width 2.0*10^-15 meter and height 30.0 MeV. What is the tunneling probability if the energy of the alpha particle is 18.0MeV below the top of the...
  46. G

    Alpha Significance: Understanding & Analyzing Data Set

    Homework Statement What conclusions can be drawn from this data set? What assumptions are you making? Homework Equations http://i.imgur.com/M9YQGAF.png I hope this is legible. The Attempt at a Solution The solution is what I'm having trouble with. I just don't get how that test statistic has...
  47. S

    Estimating Half-Life of Alpha Decay: Nucleus ##^{252}_{98}Cf##

    Homework Statement Nucleus ##^{252}_{98}Cf## alpha decays with half life time ##t_{1/2}=2.6## years. What is the velocity of the alpha particle after the decay? Estimate the half life time of the nucleus after the decay. Homework EquationsThe Attempt at a Solution Ok, no worries about the...
  48. B

    What happens if you change the fine-structure constant?

    I've read online that the fine-structure constant (alpha) is at a sort of "goldilocks value" for life generation; if it were 4% lower, stars would not produce carbon or oxygen in their fusion, and if it were greater than 0.1, fusion simply wouldn't occur. These are interesting facts, but can...
  49. manogyana25

    Rutherford's Alpha particles experiment

    According to JJ Thomson's atomic model, Rutherford expected deflections of alpha particles through small angles. I'm unable to understand why he had expected "small angles". Can someone please explain.
  50. D

    Calculate angular velocities and alpha values?

    Homework Statement A lightweight bar, stiff stick of length L, at either end are two small spheres of mass ##m_{1} = m_{2} = m##. Bar may turn in vertical horizontal axis passing through point O on the way its a bar ##\frac{L}{3}##. At first, the bar is vertical. Due to a slight impact, the...
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