Atoms - Quiz 4

ATOMS QUIZ-4

Dear Readers,

JEE Advanced Physics Syllabus can be referred by the IIT aspirants to get a detailed list of all topics that are important in cracking the entrance examination. JEE Advanced syllabus for Physics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with day-to-day experiences. In comparison to the other two subjects, the syllabus of JEE Advanced for physics is developed in such a way so as to test the deep understanding and application of concepts.

Q1. The ratio of maximum to minimum possible radiation energy in Bohr’s hypothetical hydrogen atom is equal to

•  2
•  4
•  4/3
•  3/2

Solution

Q2. In order to determine the value of E₀, a scientist shines photon (“light particles”) of various energies at a cloud of atomic hydrogen. Most of the hydrogen atoms occupy the ground state. A detector records the intensity of light transmitted through that cloud; see figure (a). Figure (b) is a graph of part of the scientist’s data, showing the intensity of the transmitted light as a function of the photon energy. A hydrogen atom’s electron is likely to absorb a photon only if the photon gives the electron enough energy to knock it into a higher shell.According to this experiment, what is the approximate value of E₀?

•   1.6×10^(-18) J
•  2.1×10^(-18) J
•  3.2×10^(-18) J
•  6.4×10^(-18) J

Solution

Q3. Suppose two deuterons musts get as close as 10^(-14) m in order for the nuclear force to overcome the repulsive electrostatic force. The height of the electrostatic barrier is nearest to

•  0.14 MeV
•  2.3 MeV
•  1.8 x 10 MeV
•  0.56 MeV

Q34. An electron of energy 11.2 eV undergoes an inelastic collision with a hydrogen atom in its ground state. [Neglect recoiling of atom as m_H≫m_e]. Then in this case

•  The outgoing electron has energy 11.2 eV
•  The entire energy is absorbed by the H atom and the electron stops
•  10.2 eV of the incident electron energy is absorbed by the H atom and the electron would come out with 1.0 eV energy
•  None of the above

Solution
(c) As the collision is inelastic, it means a part of kinetic energy is transformed into some other form due to collision. In this case, the kinetic energy of incident electron can be absorbed by H atom and it can absorb only 10.2 eV out of 11.2 eV, so that it can reach to 1st excited state and the electron leaves with remaining, i.e., 1.0 eV

Q35. The energy of an electron in an excited hydrogen atom is -3.4 eV. Then, according to Bohr’s Theory, the angular momentum of this electron, in Js, is

•  2.11×10^(-34)
•  3×10^(-34)
•  1.055×10^(-34)
•  0.5×10^(-34)

Solution

Q6. If an X-ray tube operates at the voltage of 10 kV, find the ratio of the de Broglie wavelength of the incident electrons to the shortest wavelength of X-rays produced. The specific charge of electron is 1.8×10¹¹ C kg

• 1
• 0.1
• 1.8
• 1.2
Solution

Q7. In Bohr’s model of hydrogen atom, let PE represent potential energy and TE the total energy. In going to a higher orbit,

•  PE increases, TE decreases
•  PE decreases, TE increases
•  PE increases, TE increases
•  PE decreases, TE decreases

Solution
(c) Potential energy =-C/r² and total energy =-Rhc/n². With higher orbit, both r and n increase. So, both become less negative; hence both increase

Q8. The recoil of speed of hydrogen atom after it emits a photon in going from n=2 state to n=1 state is nearly [Take R_∞=1.1×10⁷ m^(-1) and h=6.63×10^(-34) Js]

•  1.5 ms^(-1)
•  3.3 ms^(-1)
•  4.5 ms^(-1)
•  6.6 ms^(-1)

Solution

Q9. Transitions between three energy levels in a particular atom give rise to three spectral lines of wavelength, in increasing magnitudes, λ₁,λ₂ and λ₃. Which one of the following equations correctly relates λ₁,λ₂ and λ₃?

•  λ₁=λ₂-λ₃
•  λ₁=λ₃-λ₂
•  1/λ₁ =1/λ₂ +1/λ₃
•  1/λ₁ =1/λ₃ -1/λ₂

Solution

Q10. If the K_α radiation of Mo (Z=42) has a wavelength of 0.71 Å find the wavelength of the corresponding radiation of Cu (Z=29)

•  1 Å
•  2 Å
•  1.52 Å
• 1.25 Å

Solution
(b) Use Moseley’s law