Question

Class 12 Physics MCQ Questions of Atoms with Answers?

Answer 1

Students can solve these Class 12 Physics MCQ Questions of Atoms with Answers and assess their preparation level. MCQ Questions with Answers are prepared as per the newest Exam Pattern. Solving the class 12 Physics MCQ Questions of Atoms with Answers will be of extreme help as you’ll remember all the concepts. These MCQ Questions for class 12 with answers for a fast revision of the Chapter thereby helping you to boost subject knowledge.

Let’s starts practice MCQ Questions for class 12 Physics Atoms for exam preparation. It helps to understand the Exam Pattern.

Practice MCQ Question for Class 12 Physics chapter-wise

1. The energy equivalent to one atomic mass unit is :

(a) 1.6 × 10^-19 J
(b) 6.02 × 10²³ J
(c) 9.31 MeV
(d) 931 MeV

2. Who explained the splitting of special lines in magnetic field?

(a) Zeeman
(b) Bohr
(c) Summerfield
(d) Einstein

3. The concept of electron spin was introduced by:

(a) Becquerel
(b) Goudsmit
(c) Millikan
(d) Uhlenbeek and Goudsmit

4. The principle that a quantum orbital cannot be occupied by more than two electrons was given by:

(a) Pauli
(b) Millikan
(c) Hund
(d) None of these

5. For ionization of excited Hydrogen atom, the, required energy is:

(a) a little less than 13.6
(b) equal to 13.6
(c) more than 13.6
(d) 3.4 or less

6. Natural radioactivity was discovered by:

(a) Joliot
(b) Becquerel
(c) Pauli
(d) None of these

7. Transmutation of nuclei was discovered by:

(a) Rutherford
(b) Becquerel
(c) Pauli
(d) None of these

8. The energy equivalent to mass defect is called :

(a) binding energy
(b) internal energy
(c) external energy
(d) enthalpy

9. In Bohr’s model of an atom which of the following is an integral multiple of \(\frac{h}{2\pi}\)?

(a) Kinetic energy
(b) Radius of an atom
(c) Potential energy
(d) Angular momentum

10. The transition of electron from n = 4, 5, 6, ………. to n = 3 corresponds to

(a) Lyman series
(b) Balmer series
(c) Paschen series
(d) Bracket series

11. The first model of atom in 1898 was proposed by

(a) Ernst Rutherford
(b) Albert Einstein
(c) J.J. Thomson
(d) Niels Bohr

12. In Geiger-Marsden scattering experiment, the trajectory traced by an a-particle depends on

(a) number of collision
(b) number of scattered a-particles
(c) impact parameter
(d) none of these

13. Which of the following spectral series falls within the visible range of electromagnetic radiation?

(a) Lyman series
(b) Balmer series
(c) Paschen seriee
(d) Pfund series

14. In a hydrogen atom, the radius of nth Bohr orbit is rn. The graph between log(r_n/r₁) and log n will be

15. The number of waves, contained in unit length of the medium is called

(a) Wave number
(b) Wavelength
(c) Amplitude
(d) Frequency

16. The Lyman transitions involve

(a) largest changes of energy
(b) smallest changes of energy
(c) largest changes of potential energy
(d) smallest changes of potential energy

17. According to classical theory, the circular path of an electron in Rutherford atom model is

(a) spiral 
(b) circular
(c) parabolic 
(d) straight line

18. The electrons of Rutherford’s model would be expected to lose energy because, they

(a) move randomly
(b) jump on nucleus
(c) radiate electromagnetic waves
(d) escape from the atom

19. Hydrogen atom excites energy level from fundamental state to n = 3. Number of spectral lines according to Bohr, is

(a) 4 
(b) 3 
(c) 1 
(d) 2

20. In the Geiger-Marsden scattering experiment the number of scattered particles detected are maximum and minimum at the scattering angles respectively at

(a) 0° and 180°
(b) 180° and 0°
(c) 90° and 180°
(d) 45° and 90°

21. Which source is associated with a line emission spectrum? 

(a) Electric fibre 
(b) Neon street Sign
(c) Red traffic light
(d) Sun

22. When electron jumps from n = 4 to n = 2 orbit, we get

(a) second line of Lyman series
(b) second line of Balmer series
(c) second line of Paschen series
(d) an absorption line of Balmer series

23. The spectrum obtained from a sodium vapour lamp is an example of

(a) band spectrum
(b)  continuous spectrum
(c) emission spectrum
(d) absorption spectrum

24. To explain his theory, Bohr used

(a) conservation of linear momentum
(b) conservation of angular momentum
(c) conservation of quantum  frequency
(d) conservation of energy

25. The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by 

(a) Planck
(b) J.J. Thomson
(c) Einstein
(d) Millikan

Answer 2

1. Answer : (d) 931 MeV

Explanation : 1 a.m.u = 931 MeV

2. Answer : (a) Zeeman

Explanation: Splitting of spectral lines in electric field is called Stark effect while splitting of spectral lines under the influence of magnetic field is called Zeeman effect.

3. Answer : (d) Uhlenbeek and Goudsmit

Explanation: Ralph Kronig had come up with the idea of electron spin several months before George Uhlenbeck and Samuel Goudsmit.

4. Answer : (a) Pauli

Explanation: The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.

5. Answer : (d) 3.4 or less

Explanation: The energy of the electron is – 3.4 eV in first excited state and the its magnitude is less for higher excited state.

6. Answer : (b) Becquerel

Explanation: In one of the most well-known accidental discoveries in the history of physics, on an overcast day in March 1896, French physicist Henri Becquerel opened a drawer and discovered spontaneous radioactivity.

7. Answer : (a) Rutherford

Explanation: Nuclear transmutation was first consciously applied to modern physics by Frederick Soddy when he, along with Ernest Rutherford, discovered that radioactive thorium was converting itself into radium in 1901.

8. Answer : (a) binding energy

Explanation: The energy equivalent to the mass defect of a nucleus is known as the binding energy, which is the energy required to dismantle the nucleus into its individual constituent nucleons or, alternatively, the energy released when the nucleons come together to form the nucleus.

9. Answer : (d) Angular momentum

Explanation: Angular momentum \(L=mvr=\frac{nh}{2\pi}\)

10. Answer :(c) Paschen series

Explanation: In transition from n₁ = 3 and n₂ = 4, 5, 6 ,Infrared radiation of Paschen spectral is emitted.

11. Answer : (c) J.J. Thomson

Explanation: The first model of an atom was given by JJ Thomson. According to him, an atom consists of a sphere of positive charge with negatively charged electrons embedded in it.

12. Answer : (c) impact parameter

Explanation: Trajectory of α-particle depends on impact parameter which is the perpendicular distance of the initial velocity vector of the α particle from the centre of the nucleus. For small impact parameter a particle close to the nucleus and suffers larger scattering.

13. Answer : (b) Balmer series

Explanation: The spectral line of wavelength 4860 Å lies in the visible region. Since Balmer series lies in the visible region of the spectrum. Therefore, Balmer series give spectral line of 4860 Å.

14. Answer : 

Explanation: \(r_n\propto n^2\)

15. Answer : (a) Wave number

Explanation: When wavelength is measured in metres, \(\frac{1}{\lambda}\) represents the number of waves of the wave train to be found in a length of one metre or, if measured in centimetres, the number in one centimetre. This number is called the wavenumber of the spectrum line.

16. Answer : (a) largest changes of energy

Explanation: In Lyman transitions, electron have to return to ground state, i.e., n = 1. So, they involve largest changes of energy.

17. Answer : (a) spiral 

Explanation: Due to the continuous loss of energy the electron will move along a spiral path towards the nucleus.

18. Answer : (c) radiate electromagnetic waves

Explanation: The motion of the electrons in the Rutherford model was unstable because, according to classical mechanics and electromagnetic theory, any charged particle moving on a curved path emits electromagnetic radiation; thus, the electrons would lose energy and spiral into the nucleus.

19. Answer : (b) 3 

Explanation: Number of spectral lines

\(N_E=\frac{n(n-1)}{2}\)​

\(=\frac{3(3-1)}{2}\)

= 3​​​​​​

20. Answer : (a) 0° and 180°

Explanation: The number of scattered particles detected will be maximum at the angle of scattering θ=0∘ and minimum at \(\theta=\)180^∘.

21. Answer : (b) Neon street Sign

Explanation: Neon street sign is a source of line emission spectrum.

22. Answer : (b) second line of Balmer series

Explanation: For lyman and paschen series are not possible and second line of Balmer series is obtained for n_i = 4 and n_f = 2
For absorption, the electron is raised from n = 2 to a higher level.

23. Answer : (c) emission spectrum

Explanation: A spectrum is observed, when light coming directly from a source is examined with a spectroscope. Therefore spectrum obtained from a sodium vapour lamp is emission spectrum.

24. Answer : (b) conservation of angular momentum

Explanation: Bohr postulated that the angular momentum of the electron is conserved.

25. Answer : (d) Millikan

Explanation: Robert Millikan's oil drop experiment demonstrated this fact directly, and measured the elementary charge.

Click here to practice  MCQ Question for Atoms Class 12