Welcome to your ATOMS AND NUCLEI
1.
The radius of the first Bohr orbit of hydrogen is r. The radius of the third orbit is:
2.
A neutron is more stable inside nucleus than free because:
3.
A nucleus X(Z,A) undergoes β⁺ decay. The daughter nucleus is:
4.
In Bohr model, angular momentum of electron is quantized as:
5.
Fusion of hydrogen nuclei requires very high temperature mainly to:
6.
Ratio of speeds of electrons in n=1 and n=4 orbits of hydrogen:
7.
A free neutron decays into:
8.
A radioactive element has half-life 10 days. After 50 days, remaining fraction is:
9.
A radioactive sample has activity A. After two half-lives, the activity becomes:
10.
A radioactive isotope decays to 1/16 in 2 hours. Half-life is:
11.
Neutron-to-proton ratio in stable heavy nuclei is approximately:
12.
A radioactive nuclide has decay constant 0.693/day. Its half-life is:
13.
A radioactive sample has decay constant λ. Time taken to reduce to 1/e of initial value:
14.
If radius of Li nucleus (A = 7) is R, radius of Au nucleus (A = 197) is:
15.
The ratio of nuclear densities of Fe and U is:
16.
In Bohr’s model, total energy of electron in any orbit is:
17.
If R₀ is nuclear radius constant, volume of nucleus is proportional to:
18.
The energy released in fusion is mainly due to:
19.
The atomic spectrum is due to:
21.
The ratio of frequencies of radiation emitted in transitions n=3→1 and n=4→1 for H-atom is:
22.
The nuclear force is:
23.
Binding energy per nucleon is maximum for:
24.
The number of alpha particles emitted when U-238 becomes Pb-206:
25.
The ratio of radii of hydrogen atom in n=5 to n=1 is:
26.
Nuclear fission is caused due to:
27.
Nuclear radius varies as:
28.
Radiation least penetrating in matter is:
29.
A nucleus splits into two equal fragments. Its binding energy per nucleon increases because:
30.
If binding energy of He-4 is 28.3 MeV, binding energy per nucleon is:
31.
Ionization energy of hydrogen is 13.6 eV. Wavelength of emitted photon for transition n=3 → n=2 is:
32.
When electron jumps from n=4 to n=2 in hydrogen, the emitted photon is in:
33.
Half-life of a radioactive sample is 20 min. Activity reduces to 1/8 in:
34.
If the mass of a nucleus is less than sum of nucleons, the difference is:
35.
Which decay increases atomic number by 1?
36.
If 75% of a radioactive sample decays in time t, its half-life is:
37.
In α-decay, kinetic energy is shared between α particle and daughter nucleus. The α particle receives more KE because:
38.
Energy of electron in hydrogen’s second orbit is –3.4 eV. Energy in the fourth orbit is:
39.
Nucleus A (mass defect = 0.8 u) and B (mass defect = 0.2 u). Which is more stable?
40.
The number of neutrons emitted in fission of U-235 by slow neutron is typically:
41.
Kinetic energy of α particle emitted in decay increases if:
42.
Ionization energy of He⁺ is:
43.
Hydrogen spectrum Lyman series lies in which region?
44.
Number of β-decays when Th-232 becomes Pb-208 after emitting 6 α-particles:
45.
Wavelength of emitted photon for transition n=5→2 in hydrogen lies in:
