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Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity.

Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity. Wrapped photographic plate showed clear silhouettes, when developed, of the uranium salt samples stored atop it.

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Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity.

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  1. Henri Becquerel(1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity. Wrapped photographic plate showed clear silhouettes, when developed, of the uranium salt samples stored atop it. • 1896 While studying the photographic images of various • fluorescent and phosphorescent materials, Becquerel • finds potassium-uranyl sulfate spontaneously emits • radiation capable of penetrating • thick opaque black paper • aluminum plates • copper plates • Exhibited by all known compounds of uranium • (phosphorescent or not) and metallic uranium itself.

  2. 1898Marie Curie discovers thorium (90Th) Together Pierre and Marie Curie discover polonium (84Po) and radium (88Ra) 1899Ernest Rutherfordidentifies 2 distinct kinds of rays emitted by uranium:  - highly ionizing, but completely absorbed by 0.006 cmaluminum foil or a few cm of air  - less ionizing, but penetrate many meters of air or up to a cm of aluminum. 1900P. Villard finds in addition to  rays, radium emits  - the least ionizing, but capable of penetrating many cm of lead, several feet of concrete

  3. F = q vB sinq Magnitude of Magnetic ForceLorentz Law Magnetic force is related to q, v and B Experimental observations: • force depends on the direction of v relative to B • if v is parallel to B  F = 0 • if v is perpendicular to B  F = Fmax • if v is at angle q from B  F = Fmax sinq

  4. F = q vB sinq Direction of Magnetic Force out of page in to page tail 3D Drawing vectors in head Direction of magnetic force is “sideways” • force is perpendicular to both v and B • use “right-hand” or “left-hand rule” to find its direction

  5. B B B x x x x x x x x x x x x x x x x x x ® ® ® ® ® ® ® ® ® ® ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ v v v ´ q q q F F = 0 F Right Hand Rule Examples

  6. B v v v B B What is the direction of the force on a positive charge when the velocity and magnetic field B are indicated as below? ABCDE) none of these

  7. B v B B v v What is the direction of the force on a positive charge when the velocity and magnetic field B are indicated as below? ABCDE) none of these

  8. A positivelycharged beam enters a magnetic field region as shown. What is the direction of B? A + y (up) B– y (down) C + x (right) D + z (out of page) E – z (into page) y x z

  9. An uncharged particle enters a region with the magnetic field shown. What path will it follow? A x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x B field B D C

  10. A charged particle moves in a straight line through some region of space. The net magnetic field in this region must be zero. T)True F) False

  11. a g B-field points into page b From these observations alone, what definite conclusions can be made? A. as are positively charged, bs negative. B. as are negatively charged, bs positive. C. can only say a,b oppositely charged.

  12. X A B field B Y C Z Imagine three particles A, B and C all with the same mass, but different charges. (Particle B is neutral). When A enters the magnetic field, it follows path Z. When particle B enters the magnetic field, it will follow path A) X B) Y C) Z When particle C enters the magnetic field, it will follow path A) X B) Y C) Z

  13. X A B field B Y C Z Imagine three particles A, B and C all with the same mass, but different charges. (Particle B is neutral). When A enters the magnetic field, it follows path Z. When particle B enters the magnetic field, it will follow path A) X B) Y C) Z When particle C enters the magnetic field, it will follow path A) X B) Y C) Z The answer to the first question is (2). A magnetic field exerts forces on moving charges. If there is no charge (as for a neutral particle) there is no force. The Lorentz Force Law says that F=qvB when v and B are perpendicular. If q=0, the F=0. The answer to the second question is (3). The charge of C is opposite that of A, which we can write as q(C) = q(A), so F(C) = F(A). A minus sign on a vector means that it points in the opposite direction. So if A follows path X, then C must follow path Z.

  14. X Y Z A B field out of page B Particles A and B have the same charge, but particle B has more mass. When particle A enters the magnetic field, it travels along line Y. When particle B enters the magnetic field, it will follow line A) X B) Y C) Z

  15. a g B-field points into page b • From these observations alone, do the • magnitude of their charges compare? • A. qa<qb • B. qa=qb • C. qa>qb • D. you cannot determine this

  16. a g B-field points into page b From these observations alone, what definite conclusions can be made? A. as are more massive than bs. B. as are more massive than gs. C. bs are more massive than as. D. Masses cannot be directly compared.

  17. 1900-01 Studying the deflection of these rays in magnetic fields, Becquerel and the Curies establish  rays to be charged particles Using the procedure developed by J.J. Thomson in 1887 Becquerel determined the ratio of charge q to mass m for : q/m = 1.76×1011 coulombs/kilogram identical to the electron! : q/m = 4.8×107 coulombs/kilogram 4000 times smaller! Noting helium gas often found trapped in samples of radioactive minerals, Rutherford speculated that  particles might be doubly ionized Helium atoms (He++) 1906-1909 Rutherford and T.D.Royds develop their “alpha mousetrap” to collect alpha particles and show this yields a gas with the spectral emission lines of helium!

  18. a g b • as are ionized Helium (bare Helium nuclei) • 2-protons, 2-neutrons (positively charged) • bs are simply electrons(negatively charged) • qa= -2qb • ma=7296mb

  19. 1911-12 • Austrian physicist Victor Hess, of the Vienna University, and 2 assistants, carried Wulf ionization chambers up in • a series of hydrogen balloon flights. • taking ~hour long readings at several altitudes • both ascending and descending • radiation more intense above 150 meters than at sea level • intensity doubled between 1000 m to 4000 m • increased continuously through 5000 meters Dubbed this “high” level radiation Höhenstrahlung Hess lands following a historic 5,300 meter flight. August 7, 1912 National Geographic photograph In 1936, Hess was awarded the Nobel prize for this discovery.

  20. Cosmic ray strikes a nucleus within a layer of photographic emulsion 50mm

  21. 1913-14Werner Kolhörster of Berlin’s • Physikalisch-Technische Reichsanstalt • ascends to 9300 m (height of Mount Everest, • cruising altitude of a passenger jet!) • ionization rate 50× that at sea level! • 1925-26Robert Millikan of Caltech (winner of the 1923 • Nobel prize) initially fails to duplicate such results • over San Antonio, Texas, found “not more than • 25% of that found by European observers.” • Further high-altitude measurements made in • collaboration with Ira S. Bowen confirmed the • existence of what Millikan coined “cosmic rays”. Ionization chambers grow more robust and reliable. Automated to work and be recorded remotely.

  22. 1911 Rutherford’s assistant Hans Geiger develops a device registering the passage of ionizing particles. 1924Walter Bothe and Geiger use multiple Geiger counters to establish the tracks followed by electron beams 1928-29Bothe and Wernre Kolhörser build Geiger telescopes and announce cosmic “rays” contain charged particles

  23. 1927-28 Jacob Clay travels from Genoa to the Dutch colony • of Java with an ionization chamber and finds • intensity drops ~6% • minimum at magnetic equator • 1929Bothe & Kolhorster • suggest Clay’s Lattitude Effect could be due to • charged primaries deflccted by earth’s magnetic field • inspired by the Norwegian • mathematician Carl Størmer’s • calculations explaining • colleague • Kristian Birkland’s • theory of the aurora • Birkland had • experimented with • electron beams and • a phosphorous-painted • globe of lodestone

  24. Geomagnetism Earth’s magnetic field is approximately that of a bar magnet. • Field strength is not the same everywhere stronger at the poles • Field angle is different in different locations vertical at poles, horizontal at magnetic equator • South magnetic pole is at north geographic pole Magnetic axis does not line up with rotation axis • compass correction depends on location New York 10° W Chicago 0° L.A. 18° E Magnetic poles move, and sometimes reverse direction Cause: Not fully understood, but is somehow due to motion of charged particles in Earth’s molten interior. But why aren’t poles aligned with rotation axis? Other astronomical bodies with magnetic fields: Mercury and Jupiter, The Sun, The Milky Way galaxy Location of S magnetic pole over last century

  25. 70o 80o 1948• 1975• 1995• 1904• Northwest Territories The North pole of a small magnet (compass) points towards geographic North because Earth’s magnetic South pole is up there!! The field lines of the Earth’s field are not parallel (except at the equator) to the surface of the earth “Dip Angle” The magnetic pole is not exactly at geographic north (compass corrections needed). The poles in fact drift, and occasionally reverse polarity!

  26. 1930-33 Arthur Compton (University of Chicago) conducts a worldwide sea-level (and mountain lattitude) survey of cosmic ray intensities and confirms the Latitude Effect. The 4 curves correspond to 4 seasons. Physical Review 52 [1937]:p.808 Størmer’s “cutoff energies”: only the fastest cosmics reach sea level near the equator  less energetic particles are observable at mid-latitudes  unrestricted energies in the polar regions September 21, 1932Millikan completed a series of tests on the intensity of cosmic rays at various altitudes in a Condor bomber from March Field, California.

  27. 1933-35Thomas Johnson (of the Carnegie Institute) and Bruno Rossi (Italy) independently mount Geiger counter telescope arrays to test for the east-west asymmetry predicted by Georges Lemaître (Belgian)

  28. Positive charged particles headed toward the earth from space, would tend (at mid-latitudes) to reach the surface coming down from the A. North B. South C. East D. West E. split East and West

  29. Although cosmic rays do come “from all directions”, at high altitudes near the equator the intensity is higher coming from the West than from the East! 1939Johnson speculates primaries may be protons!

  30. November 11, 1935Explorer II, a 113,000 cubic foot helium balloon ascends to a record 22,066 m while collecting atmospheric and cosmic ray data. 1937-1939 Studies of Extended Air Showers begin in France when by accident Pierre Auger and his Russian colleague Dimitry Skobeltzyn notice apparent coincidence between Cosmic Ray telescopes set up several hundred meters apart. Cloud chamber photographs byGeorge Rochesterand J.G. Wilson of Manchester University showed the large number of particles contained within such showers.

  31. 1936Millikan’s group show that at the earth’s surface showers are dominated by electrons, gammas, and X-particles capable of penetrating deep underground (to lake bottom and deep tunnel experiments) characterized there by isolated single cloud chamber tracks

  32. Definite evidence for the celestial generation of Cosmic Rays came from fortuitous timing of a few high altitude balloon studies during some spectacular solar flares.

  33. Unusual increase in Cosmic ray intensity associated with an intense solar flare observed February 28, 1942 the same sunspot associated with this flare erupts again March 7, 1942 Similarly the June 4, 1946solar prominence is followed by another eruption July 25, 1946 and the solar flare event of November 19, 1949 is also captured by airborne cosmic ray instruments each accompanied by a Sudden Ionospheric Disturbance which interrupts radio communications on earth

  34. During the June 1946 prominence, ultraviolet radiation and x-rays arrived simultaneous to the visual observation of the flare. Why? Radio interference began immediately. Charged particles causing radio blackouts arrived about 3 hours later. But ground-based monitoring stations at low magnetic latitudes observed no increase. Why? However on November 14, 1960Explorer VII detects solar flares causing “extremely severe” magnetic disturbances in the Earth's atmosphere. The sea level neutron counter at Deep River, Canada records: J.F.Steljes, H.Carmichael, K.McCracken, Journal of Geophysical Research 66 [1961]:p.1363 and the National Bureau of Standards measures extensive attenuation of radio transmissions

  35. May 11, 1950 A Naval Research Viking research rocket fired from the U.S.S. Norton Sound near Jarvis Island in the Pacific collects cosmic ray and pressure and temperature data. 1952-57James A. Van Allen (The University of Iowa) reports the first high altitude survey of total cosmic-ray intensity and latitude variation of heavy nuclei in primary cosmic radiation, from his “Rockoon” (balloon-launched rocket). February - March, 1958 U.S. Satellites Explorer I and II carry Geiger-Müller counters for Van Allenlooping through highly eccentric (50 km perigee, 2600 km apogee) orbits every 2½ hours.  Cosmic ray intensities increase steadily with altitude until 2000 km when counters suddenly registerednothing.  Lab tests of duplicate counters suggested they had been overloaded by a region with a sudden 15000× increase in cosmic rays!

  36. 1958 Explorer IV and Sputnik III confirm, what is • eventually mapped as 2 gigantic radiation belts • of trapped ions. • October 13, 1959 • Explorer VII was launched. into an Earth orbit. By late • December its data reveals • inner belt mostly protons • outer belt mostly electrons

  37. July 31, 1961 NASA funds high-altitude balloon measurements of the proton and alpha-particle spectrum of primary cosmic radiation conducted by the University of Chicago above Uranium City, Saskatchewan, Canada. August 17, 1961 Explorer XII radios data on magnetic fields and cosmic rays from a 54,000 mile apogee (and 170 mile perigee). 1962 Enroute to VenusMariner II detects a continuously flowing solar wind of fast and slow streams, cycling in 27 day intervals (the rotational period of the Sun). July 1969 Apollo 11 astronauts trap cosmic ray particles on exposed aluminum foil, returned to earth for analysis of its elemental and isotopic composition. With no atmosphere or magnetic fieldof its own, the moon’s surface provides a constant bombardment of particles.

  38. March 3, 1972 Pioneer 10 launched -on its flyby mission, studies Jupiter's magnetic field and radiation belts. December 1972 Apollo 17’s lunar surface cosmic ray experiment measured the flux of low energy particles in space (foil detectors brought back to Earth for analysis.. October 26, 1973 IMP-8 launched. Continues today measuring cosmic rays, Earth’s magnetic field, and the near-Earth solar wind from a near-circular, 12-day orbit (half the distance to the moon). October 1975 to the present GOES (Geostationary Orbiting Environmental Satellite) An early warning system which monitors the Sun's surface for flares. 1977 The Voyager 1 and 2 spacecraft are launched. Each will explore acceleration processes of charged particles to cosmic ray energies.

  39. August 31, 1991 Yohkoh spacecraft launched - Japan/USA/England solar probe - studied high-energy radiation from solar flares. July 1992 SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer) into polar orbit. By sampling interplanetary and magnetospheric particles, contributes to our understanding of nucleosynthesis and the acceleration of charged particles. July 1992 IMAX (Isotope Matter-Antimatter eXperiment) balloon- borne superconducting magnetic spectrometer measured the galactic cosmic ray abundances of protons, anti-protons, hydrogen, and helium isotopes. August 25, 1997 Advanced Composition Explorer (ACE) was launched!

  40. THE COSMIC RAY DEFLECTION SOCIETY OF NORTH AMERICA http://www.geocities.com/SunsetStrip/1483/

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