NEET Physics Atomic Structure and Rutherfords Nuclear Model MCQs Set A

Question: Rutherford’s a-particle experiment showed that the atoms have
a) Nucleus
b) Electrons
c) Proton
d) Neutron
Answer: Nucleus

Question: Rutherford’s atomic model was unstable because
a) electrons do not remain in orbit
b) nuclei will break down
c) orbiting electrons radiate energy
d) electrons are repelled by the nucleus
Answer: electrons do not remain in orbit

Question: As one considers orbits with higher values of n in a hydrogen atom, the electric potential energy of the atom
a) increases
b) does not increase
c) decreases
d) remains the same
Answer: increases

Question: The significant result deduced from the Rutherford's scattering experiment is that
a) whole of the positive charge is concentrated at the centre of atom
b) there are neutrons inside the nucleus
c) electrons are embedded in the atom
d) electrons are revolving around the nucleus
Answer: whole of the positive charge is concentrated at the centre of atom

Question:

a)

b)

c)

d) v

Answer:

Question:

a) 180º
b) 0º
c) 270º
d) 90º
Answer: 180º

Question: Which of the following parameters is the same for all hydrogen-like atoms and ions in their ground states?
a) Orbital angular momentum of the electron
b) Energy of the atom
c) Speed of the electron
d) Radius of the orbit
Answer:  Orbital angular momentum of the electron

Question:

a) 10^–12 cm
b) 10^–10 cm
c) 10^–20 cm
d) 10^–15 cm
Answer: 10^–12 cm

Question: The distance of closest approach of a certain nucleus is 7.2 fm and it has a charge of 1.28 × 10^–17 C. The number of neutrons inside the nucleus of an atom is
a) 136
b) 142
c) 140
d) 132
Answer: 136

Question:  Assertion : Electrons in the atom are held due to coulomb forces.
Reason : The atom is stable only because the centripetal force due to Coulomb's law is balanced by the centrifugal force.
a) If Assertion is correct but Reason is incorrect
b) If both the Assertion and Reason are incorrect
c) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
d) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion
Answer: If Assertion is correct but Reason is incorrect

Question: In an atom, the two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the time taken by them to complete one revolution is
a) 1/8
b) 8/1
c) 4/1
d) 1/4
Answer: 1/8

Question:

a) 8.4 × 10^–15 m
b) 4.2 × 10^–15 cm
c) 8.4 × 10^–15 cm
d) 4.2 × 10^–15 m
Answer: 8.4 × 10^–15 m

Question:

a) 4 only
b) 1 and 4
c) 2 and 3
d) 3 and 4
Answer: 4 only

Question:

a)

b)

c)

d) None of these

Answer : 

Comprehension Based

Paragraph -I

Scientists are working hard to develop nuclear fusion reactor. Nuclei of heavy hydrogen, ²₁H known as deuteron and denoted by D can be thought of as a candidate for fusion reactor. The DD reaction is ²₁H + ²₁H → ³₂He + n + energy. In the core of fusion reactor, a gas of heavy hydrogen is fully ionized into deuteron nuclei and electrons. This collection of ²₁H nuclei and electrons is known as plasma. The nuclei move randomly in the reactor core and occasionally come close enough for nuclear fusion to take place. Usually, the temperatures in the reactor core are too high and no material wall can be used to confine the plasma. Special techniques are used which confine the plasma for a time t₀ before the particles fly away from the core. If n is the density (number/volume) of deuterons, the product nt₀ is called Lawson number. In one of the criteria, a reactor is termed successful if Lawson number is greater than 5×10¹⁴s cm^–3. It may be helpful to use the following: Boltzmann constant K = 8.6 10^-5 eV / K; e²/πε₀ = 1.44 x 10^-9 eVm 

Question: In the core of nuclear fusion reactor, the gas becomes plasma because of:
a. strong nuclear force acting between the deuterons
b. Coulomb force acting between the deuterons
c. Coulomb force acting between deuteron-electron pairs
d. the high temperature maintained inside the reactor core
Answer : D

Question: Assume that two deuteron nuclei in the core of fusion reactor at temperature T are moving towards each other, each with kinetic energy 1.5 kT; when the separation between them is large enough to neglect Coulomb potential energy. Also neglect any interaction from other particles in the core. The minimum temperature T required for them to reach a separation of 4×10^–15 m is in the range:
a. 1.0 × 10⁹ K < T < 2.0 × 10⁹ K
b. 2.0 × 10⁹ K < T < 3.0 × 10⁹ K
c. 3.0 × 10⁹ K < T < 4.0 × 10⁹ K
d. 4.0 × 10⁹ K < T < 5.0 × 10⁹ K
Answer : A

Question: Results of calculations for four different designs of a fusion reactor using D-D reaction are given below. Which of these is most promising based on Lawson criterion?
a. Deuteron density = 2.0×10¹² cm^–3, confinement time = 5.0×10^–3 s
b. Deuteron density = 8.0 × 10¹⁴ cm^–3, confinement time = 9.0×10^–1 s
c. Deuteron density = 4.0 × 10²³ cm^–3 , confinement time = 1.0 × 10^–11 s
d. Deuteron density = 1.0 × 10²⁴ cm^–3 , confinement time = 4.0×10^–12s
Answer : D

Paragraph -II

The key feature of Bohr’s theory of spectrum of hydrogen atom is the quantization of angular momentum when an electron is revolving around a proton. We will extend this to a general rotational motion to find quantized rotational energy of a diatomic molecule assuming it to be rigid. The rule to be applied is Bohr’s quantization condition.

Question: A diatomic molecule has moment of inertia I. By Bohr’s quantization condition its rotational energy in the nth level (n = 0 is not allowed) is:

Answer : D

Question: It is found that the excitation frequency from ground to the first excited state of rotation for the CO molecule is close to 4/π x 10¹¹ Hz. Then the moment of inertia of CO molecule about its centre of mass is close to: (Take h = 2π × 10^–34J–s)
a. 2.76×10^–46 kg–m²
b. 1.87×10^–46 kg–m²
c. 4.67×10^–47 kg–m²
d. 1.17×10^–47 kg–m²
Answer : B

Question: In a CO molecule, the distance between C (mass = 12 amu) and O (mass = 16 amu), where 1 amu = 5/3 x 10^-27 kg, is close to:
a. 2.4 × 10^–10m
b. 1.9 × 10^–10m
c. 1.3 × 10^–10m
d. 4.4 × 10^–11m
Answer :