# CBSEtips.in

## Thursday, 28 January 2021

### CBSE Class 12 Physics - MCQ and Online Tests - Unit 12 - Atoms

#### CBSE Class 12 Physics – MCQ and Online Tests – Unit 12 – Atoms

Every year CBSE conducts board exams for 12th standard. These exams are very competitive to all the students. So our website provides online tests for all the 12th subjects. These tests are also very effective and useful for those who preparing for competitive exams like NEET, JEE, CA etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE Class 12 syllabus. While attempting these our students can identify the weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly.

#### CBSE Class 12 Physics – MCQ and Online Tests – Unit 12 – Atoms

Question 1.
According to Bohr’s theory of hydrogen atom, the radius r of stationary orbit are related to principal quantum number n as:
(a) rg ∝ $$\frac{1}{n^2}$$
(b) rg ∝ $$\frac{1}{n}$$
(c) rg ∝ n
(d) rg ∝ n²

Question 2.
The mass of a neutron is:
(a) 1.00866 u
(b) 1.0866 u
(c) 1.866 u
(d) 0.1866 u

Question 3.
Fg and Fe represents the gravitational and electrostatic force respectively between two electrons situated at some distance the ratio $$\frac{F_g}{F_e}$$ is if the order of:
(a) 9.8
(b) 109
(c) 1042
(d) 10-42

Question 4.
(a) Joliot
(b) Becquerel
(c) Pauli
(d) None of these

Question 5.
P-decay produces:
(a) isobars
(b) isotopes
(c) isotones
(d) All the above

Question 6.
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

Question 7.
Isobars have the same:
(a) A
(b) Z
(c) N
(d) All the above

Question 8.
(a) Joliot
(b) Becquerel
(c) Pauli
(d) None of these

Question 9.
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

Question 10.
The total energy that will be released if a nucleus is built from its constituents is called the:
(a) binding energy of the nucleus
(b) binding energy of the solid
(c) binding energy of the atom
(d) None of these

Answer: (a) binding energy of the nucleus

Question 11.
Who explained the splitting of special lines in magnetic field?
(a) Zeeman
(b) Bohr
(c) Summerfield
(d) Einstein

Question 12.
An atom stays in an excited state for about:
(a) 10 micro seconds
(b) 10 milli seconds
(c) 10 nano seconds
(d) 10 seconds

Question 13.
Transmutation of nuclei was discovered by:
(a) Rutherford
(b) Becquerel
(c) Pauli
(d) None of these

Question 14.
The energy equivalent to mass defect is called :
(a) binding energy
(b) internal energy
(c) external energy
(d) enthalpy

Question 15.
Isotones have the same:
(a) A
(b) Z
(c) N
(d) All the above

Question 16.
The binding energy of $$_{2}^{4}$$He is about:
(a) 28.3 eV
(b) 28.3 MeV
(c) 28.3 J
(d) 2.83 MeV

Question 17.
The binding energy of a deuteron is about:
(a) 2.22 MeV
(b) 2.22 J
(c) 2.22 eV
(d) None of these

Question 18.
Half-life of a substance depends on:
(a) pressure
(b) temperature
(c) density
(d) None of these

Question 19.
The concept of electron spin was introduced by:
(a) Becquerel
(b) Goudsmit
(c) Millikan
(d) Uhlenbeek and Goudsmit

Question 20.
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