# Topic: Atoms (Test 1)

Topic: Atoms
Topic: Atoms Tag: CBSE 12TH PHYSICS
Q.1
The ground state energy of hydrogen atom is –13.6 eV. What are the kinetic and potential energies of the electron in this state?
A. 14.6 eV, –27.2 eV
B. 13.1 eV, –29.2 eV
C. 13.6 eV, –27.2 eV
D. 14.6 eV, –29.2 eV
Explaination / Solution:
No Explaination.

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Q.2
A hydrogen atom initially in the ground level absorbs a photon, which excites it to the n = 4 level. Determine the wavelength and frequency of photon
A.  Hz.
B.  Hz.
C. Hz.
D. Hz.
Explaination / Solution:
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Q.3
Using the Bohr’s model calculate the speed of the electron in a hydrogen atom in the n = 1, 2, and 3 levels.
A. 2.28  m/s; 1.29  m/s; 7.22  m/s
B. 2.38  m/s; 1.39  m/s; 7.37  m/s
C. 2.08  m/s; 1.00  m/s; 7.20  m/s
D. 2.18  m/s; 1.09  m/s; 7.27  m/s
Explaination / Solution:
No Explaination.

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Q.4
Using the Bohr’s model Calculate the orbital period of the electron in a hydrogen atom in the n = 1, 2, and 3 levels.
A. 1.52 s; 1.22 s; 4.11 s
B. 1.72 s; 1.22 s; 4.11 s
C. 1.62 s; 1.22 s; 4.11 s
D. 1.42 s; 1.22 s; 4.11 s
Explaination / Solution:
No Explaination.

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Q.5
The radius of the innermost electron orbit of a hydrogen atom is 5.3×10–11 m. What are the radii of the n = 2 and n =3 orbits?
A. 2.32m; 4.37 m
B. 2.12m; 4.77 m
C. 2.22m; 4.27 m
D. 2.42$×$m; 4.47 m
Explaination / Solution:
No Explaination.

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Q.6
A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. What series of wavelengths will be emitted?
A. Lyman series: 143 nm and 122 nm; Balmer series: 646 nm.
B. Lyman series: 133 nm and 123 nm; Balmer series: 656 nm.
C. Lyman series: 103 nm and 122 nm; Balmer series: 656 nm.
D. Lyman series: 153 nm and 125 nm; Balmer series: 556 nm.
Explaination / Solution:
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Q.7
n accordance with the Bohr’s model, find the quantum number that characterises the earth’s revolution around the sun in an orbit of radius 1.5  m with orbital speed 3  m/s. (Mass of earth= 6.0  kg.)
A. 2.7
B. 2.9
C. 2.6
D. 2.8
Explaination / Solution:
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Q.8
Average angle of deflection of α -particles by a thin gold foil predicted by Thomson’s model is
A. incomparable to Rutherford’s model
B. about the more than predicted by Rutherford’s model
C. about the same as predicted by Rutherford’s model
D. about the less than predicted by Rutherford’s model
Explaination / Solution:
No Explaination.

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Q.9
Probability of backward scattering (i.e., scattering of α -particles at angles greater than ) predicted by Thomson’s model is
A. same as predicted by Rutherford’s model
B. more than predicted by Rutherford’s model
C. much less than predicted by Rutherford’s model
D. much more than predicted by Rutherford’s model
Explaination / Solution:
No Explaination.

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Topic: Atoms Tag: CBSE 12TH PHYSICS
Q.10
It is found experimentally that for small thickness t, the number of α-particles scattered at moderate angles is proportional to t. What clue does this linear dependence on t provide?
A. scattering is predominantly due to multiple collisions
B. scattering is predominantly due to deflecting fields being proportional to t
C. scattering is predominantly due to no collison
D. scattering is predominantly due to a single collision