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Henri Becquerel

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					 Henri Becquerel

By Lucy Martin and Alex Mogul
                     Henri’s Biography
   Henri was born on December 15, 1852 in
    Paris
   He became Professor of Applied Physics
    in the Department of Natural History in
    1892.
   Besides working with natural radioactivity
    he studied the plane polarization of light,
    the absorption of light by crystals, and
    terrestrial magnetism.
   In 1903 he was awarded half of the Nobel
    Prize while Pierre and Marie Curie were
    awarded the other half for their
    continuation of Becquerel’s study.
   Becquerel published is finding in 2 main
    books: the Annales de Physique et de
    Chimie and the Compte Rendus de
    l’Academie des Sciences.
   Henri married Mlle. Janin and had a son,
    Jean, who also became a physicist.
   He died on August 25, 1908 at Le Croisic.
            Henri’s Great Discovery
   Henri Becquerel began to study the
    effect of uranium salts on
    photographic film
   He meant to test their ability to fog
    the film when exposed to light
   Becquerel found that when exposed to
    light, the uranium salts would fog the
    photographic film
   However, bad weather one day
    interfered with the sunlight needed to
    continue the experiment
   Although no sunlight was exposed to
    the salts, the uranium still fogged the
    photographic film
   Even when Becquerel wrapped the
    film in opaque paper so no sunlight
    could enter, the uranium salts
    continued to fog the film
         Henri’s Discovery (cont’d)
   Henri experimented with diverse
    compounds of uranium and found that
    all uranium compounds produced the
    same reaction
   He concluded that the uranium atom
    was, therefore, responsible for the
    fogging reaction
   Marie and Pierre Curie continued this
    discovery, to show that the fogging
    was due to rays and particles given
    off by the uranium
   These rays and particles are called
    radiation, and the process by which
    materials, like uranium, give off these
    rays is called radioactivity
   For these valuable discoveries,
    Becquerel and the Curies together
    won the Nobel Prize in physics in
    1903
        Disproving Dalton’s Theory
   Disproved John Dalton’s theory that all
    elements are composed of tiny
    indivisible atoms, showing that atoms
    can divide
   Becquerel’s discovery of radioactivity
    led to further discoveries to refute
    Dalton’s theory
   The nuclei of radioactive atoms
    (radioisotopes) are unstable due to too
    many or too few neutrons and/or
    protons
   These unstable nuclei go through
    radioactive decay during which they
    spontaneously cast off radiation
   The particles emitted from the atom
    cause the nucleus to stabilize itself again
    and form a non-radioactive isotope
   This new isotope is of a different
    identity than the radioactive atom and
    belongs to another element
                                 QUIZ
   1. What was so amazing about Henri Becquerel’s experiment?

   2. What makes an atom radioactive, and, once you know this, how do you
    know that uranium is radioactive? What can you tell about uranium’s
    nucleus?

   3. After a radioactive atom has stabilized itself and formed a non-
    radioactive isotope is it a new element? Why?

   4. What theory did Henri’s experiment disprove?

   5. How would our lives be different if radiation was not discovered?

                                  ANSWERS
                Bibliography
   http://nobelprize.org/physics/laureates/1903/be
    cquerel-bio.html
   http://www.britannica.com/nobel/micro/59_13.
    html
   http://www.nukeworker.com/study/radiation_f
    aqs/rf04-Radiation_Related_FAQs.shtml
                                ANSWERS
   1. Even though the uranium salts had not been exposed to lights, the photographic paper still
    fogged.

   2. An atom is radioactive when the nucleus is unstable, having has too many or too few
    neutrons and/or protons, and it releases this unstable energy through radiation. The rays on the
    photographic film in Becquerel’s experiment appeared even when the uranium was not
    exposed to sunlight, so these rays must have been radiation. Therefore, uranium’s nucleus was
    unstable, and in order to stabilize, it needed to let go of the extra energy until it reached an
    ideal neutron to proton ratio. Click here and go to question #5.

   3. It is a different element. When an element gives off radiation, protons are emitted from the
    atom, therefore, the atomic number has changed.

   4. He disproved John Dalton’s theory that all elements are composed of tiny indivisible
    atoms, showing that atoms can divide.

   5. We would not have x-rays and we would lose a valuable cancer treatment.

                                         BACK TO QUIZ

				
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posted:1/24/2013
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