Atoms — Previous-Year Questions

Q1. In Rutherford's experiment, the LARGE-angle scattering of α-particles is explained by:

Q2. Distance of closest approach for a 5 MeV α on gold (Z = 79) is approximately:

Q3. The number of α-particles scattered at angle θ varies as:

Q4. Rutherford's model fails to explain:

Q5. If KE of α is quadrupled, distance of closest approach becomes:

Q1. Energy of the n=2 level of hydrogen is:

Q2. Radius of the n=3 orbit of hydrogen:

Q3. Ionization energy of He⁺ is:

Q4. Angular momentum of an electron in Bohr's third orbit is:

Q5. Bohr's model fails for:

Q1. Energy required to ionise hydrogen from its first excited state (n = 2) is:

Q2. Energy of the n=4 level of singly-ionised helium He⁺:

Q3. Transition from n=3 to n=2 in hydrogen emits a photon of energy:

Q4. How many possible emission lines arise from a hydrogen atom in the n=4 state?

Q5. Excited state of an atom is one in which:

Q1. First member of Balmer series (Hα) of hydrogen has wavelength:

Q2. Number of spectral lines emitted by an atom de-exciting from n=4:

Q3. Lyman series belongs to:

Q4. Series limit of Balmer series (in nm):

Q5. Fraunhofer lines in the solar spectrum are:

Q1. Wavelength of Hβ (n=4 → n=2) in hydrogen:

Q2. Series limit of Lyman series:

Q3. Which hydrogen line is in the VISIBLE region?

Q4. Number of distinct lines from n=5 to lower levels (hydrogen):

Q5. The 21-cm line of hydrogen corresponds to:

Q1. Photon emitted in n=3 → n=1 transition of hydrogen has energy:

Q2. Lifetime of typical 'allowed' excited atomic state:

Q3. An atom in the ground state can absorb a photon to:

Q4. An atom in the n=4 state can emit a MAXIMUM of how many distinct photons before reaching the ground state?

Q5. Stimulated emission is the basis of: