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JEE Main202127 Jul 2021Evening ShiftPhysicsNuclear PhysicsActual

Consider the following statements: A . Atoms of each element emit characteristics spectrum. B . According to Bohr's Postulate, an electron in a hydrogen atom revolves in a certain stationary orbit. C . The density of nuclear matter depends on the size of the nucleus. D . A free neutron is stable but a free proton decay is possible. E . Radioactivity is an indication of the instability of nuclei. Choose the correc

Options

  1. AA ,   B ,   C ,   D and E
  2. BA ,   B   and E only.
  3. CB and D only
  4. DA , C and E only

Correct answer

B. A ,   B   and E only.

Step-by-step solution

( A ) True, an atom of each element emits a characteristic spectrum. ( B ) True, according to Bohr's postulates m v r = n h 2 π and hence electron resides into orbits of specific radius called stationary orbits. ( C ) False, the density of the nucleus is constant. ( D ) False, A free neutron is unstable decays into proton and electron and antineutrino. ( E ) True unstable nucleus show radioactivity.

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