MCQ 1011 Mark
A nucleus of mass 218 amu in free state decays to emit an a-particle. Kinetic energy of the a-particle emitted is 6.7 MeV. The recoil energy (in MeV) of the daughter nucleus is
MCQ 1021 Mark
The composition of an a -particle can be expressed as
MCQ 1031 Mark
$_{90}^{232} $ Than isotope of thorium decays in ten stages emitting six a-particles and four b-particles in all. The end product of the decay is
- A
$_{82}^{206}{~Pb}$
- B
$_{82}^{209} {~Pb}$
- ✓
$_{82}^{208} {~Pb}$
- D
$_{83}^{209} {Br}$
AnswerCorrect option: C. $_{82}^{208} {~Pb}$
(c) $_{82}^{208} {~Pb}$
View full question & answer→MCQ 1041 Mark
A nucleus decays by $\beta^{+}$ emission followed by a gamma emission. If the atomic and mass numbers of the parent nucleus are Z and A respectively, the corresponding numbers for the daughter nucleus are respectively.
View full question & answer→MCQ 1051 Mark
The ratio activity of an element becomes $1/64^{th}$ of its original value in $60 \sec.$ Then the half life period is
- A
$5 \sec$
- ✓
$10 \sec$
- C
$20 \sec$
- D
$30 \sec$
AnswerCorrect option: B. $10 \sec$
$10 \sec$
View full question & answer→MCQ 1061 Mark
Starting with a sample of pure $66_{\mathrm{Cu}}, \frac{7}{8}$ of it decays into Zn in 15 min. The corresponding half-life is
View full question & answer→MCQ 1071 Mark
The equation $\mathrm z^{\mathrm{X}^{\mathrm{A}}} \rightarrow \mathrm{z}+1^{\mathrm{Y}^{\mathrm{A}}}+-1^{\mathrm{e}^0}+\bar{\mathrm{v}}$ is
- ✓
- B
- C
$\mathrm{e}^{-}$ capture
- D
View full question & answer→MCQ 1081 Mark
The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days
MCQ 1091 Mark
The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant
MCQ 1101 Mark
Activity of radioactive element decreased to one third of original activity $\mathrm{R}_0$ in 9 years. After further 9 years, its activity will be
- A
$\mathrm{R}_0$
- B
$\frac{2}{3} R_0$
- ✓
$\mathrm{R}_0 / 9$
- D
$\mathrm{R}_0 / 6$
AnswerCorrect option: C. $\mathrm{R}_0 / 9$
(c) $\mathrm{R}_0 / 9$
View full question & answer→MCQ 1111 Mark
The half-life of radium is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after
MCQ 1121 Mark
A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is
MCQ 1131 Mark
Carbon dating is best suited for determining the age of fossils if their age in years is of the order of
- A
$10^3$
- ✓
$10^4$
- C
$10^5$
- D
$10^6$
AnswerCorrect option: B. $10^4$
(b) $10^4$
View full question & answer→MCQ 1141 Mark
The half-life of a sample of a radioactive substance is 1 hour. If $8 \times 10^{10}$ atoms are present at t = 0, then the number of atoms decayed in the duration t = 2 hour to t = 4 hour will be
- A
$2 \times 10^{10}$
- ✓
$1.5 \times 10^{10}$
- C
- D
AnswerCorrect option: B. $1.5 \times 10^{10}$
(b) $1.5 \times 10^{10}$
View full question & answer→MCQ 1151 Mark
A radioactive decay chain starts from ${93^{Np}}^{237}$and produces ${93^{Np}}^{237}$ by successive emissions. The emitted particles can be
- ✓
Two a-particles and one b-particle
- B
Three $\beta^{+}$ particles
- C
One a particle and two $\beta^{+}$ particles
- D
One a particle and two $\beta^{-}$ particles
AnswerCorrect option: A. Two a-particles and one b-particle
(a) Two a-particles and one b-particle
View full question & answer→MCQ 1161 Mark
Radioactive nuclei that are injected into a patient collect at certain sites within its body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called
MCQ 1171 Mark
A radioactive sample at any instant has its disintegration rate 5000 disintegration per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is
MCQ 1181 Mark
Which of the following radiations has the least wavelength
MCQ 1191 Mark
A sample of radioactive element has a mass of 10 gm at an instant t = 0.The approximate mass of this element in the sample after two mean lives is
MCQ 1201 Mark
Which of the following rays are not electromagnetic waves
MCQ 1211 Mark
A radioactive substance has an average life of 5 hours. In a time of 5 hours
- A
Half of the active nuclei decay
- B
Less than half of the active nuclei decay
- ✓
More than half of the active nuclei decay
- D
AnswerCorrect option: C. More than half of the active nuclei decay
More than half of the active nuclei decay
View full question & answer→MCQ 1221 Mark
he half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its $\frac {1}{16}$ th part
View full question & answer→MCQ 1231 Mark
The half-life of $215_{ At }$ is $100 \mu s$. The time taken for the radioactivity of a sample of $215_{ At }$ to decay to $1 / 16^{\text {th }}$ of its initial value is
- ✓
$400\ \mu s$
- B
$6.3\ \mu s$
- C
$40\ \mu s$
- D
$300\ \mu s$
AnswerCorrect option: A. $400\ \mu s$
$400\ \mu s$
View full question & answer→MCQ 1241 Mark
When ${90^{Th}}^{228}$ transforms to ${83^{Bi}}^{212}$ , then the number of the emitted a- and b-particles is, respectively
View full question & answer→MCQ 1251 Mark
Nucleus produced due to a-decay of the nucleus ${Z^X}^A$ is
- A
${Z+2^Y}^{A{+4}}$
- B
${Z^Y}^A$
- ✓
${Z-2^Y}^{A{-4}}$
- D
${Z-4^Y}^{A{-2}}$
AnswerCorrect option: C. ${Z-2^Y}^{A{-4}}$
(c) ${Z-2^Y}^{A{-4}}$
View full question & answer→MCQ 1261 Mark
The activity of a sample of a radioactive material is A, at time $t_1$ and $A_2$ at time ${t}_2\left({t}_2>{t}_1\right)$. If its mean life T, then
AnswerCorrect option: C. $A_2=A_1 e^{\left(t_1-t_2\right) / T}$
(c) $A_2=A_1 e^{\left(t_1-t_2\right) / T}$
View full question & answer→MCQ 1271 Mark
If $92^{\mathrm{U}^{238}}$ undergoes successively 8 a-decays and 6 b-decays, then resulting nucleus is
- A
$82^{U^{206}}$
- ✓
$82^{\mathrm{Pb}^{206}}$
- C
$82^{\mathrm{U}^{210}}$
- D
$82^{\mathrm{U}^{214}}$
AnswerCorrect option: B. $82^{\mathrm{Pb}^{206}}$
(b) $82^{\mathrm{Pb}^{206}}$
View full question & answer→MCQ 1281 Mark
A radioactive substance emits
- A
Electromagnetic radiation
- B
Electrons revolving around the nucleus
- C
- ✓
View full question & answer→MCQ 1291 Mark
During mean life of a radioactive element, the fraction that disintegrates is
- A
- B
$\frac{1}{e}$
- ✓
$\frac{e-1}{e}$
- D
$\frac{e}{e-1}$
AnswerCorrect option: C. $\frac{e-1}{e}$
(c) $\frac{e-1}{e}$
View full question & answer→MCQ 1301 Mark
Three fourth of the active decays in a radioactive sample in 3/4 sec. The half life of the sample is
- A
$\frac{1}{2}\ sec$
- B
$1\ sec$
- ✓
$\frac{3}{8}\ sec$
- D
$\frac{3}{4}\ sec$
AnswerCorrect option: C. $\frac{3}{8}\ sec$
$\frac{3}{8}\ sec$
View full question & answer→MCQ 1311 Mark
If $N_0$ is the original mass of the substance of half life period $T_{1/2}=5$ years, then the amount of substance left after 15 years is
- ✓
$N_0/8$
- B
$N_0/16$
- C
$N_0/2$
- D
$N_0/4$
AnswerCorrect option: A. $N_0/8$
(a) $N_0/8$
View full question & answer→MCQ 1321 Mark
Half-life of a substance is 10 years. In what time, it becomes $\frac{1}{4}$ th part of the initial amount
- A
$5$ years
- B
$10$ years
- ✓
$20$ years
- D
AnswerCorrect option: C. $20$ years
(c) $20$ years
View full question & answer→MCQ 1331 Mark
A radioactive material has an initial amount 16gm. After 120 days it reduces to 1gm, then the half-life of radioactive material is
MCQ 1341 Mark
The S.I. unit of radioactivity is
MCQ 1351 Mark
In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life
MCQ 1361 Mark
10 gm of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material is
MCQ 1371 Mark
The half-life of a radioactive substance against a-decay is $1.2\times 10^7 s$ . What is the decay rate for $4\times 10^{15}$ atoms of the substance
- A
$4.6 \times 10^{12}$ atoms/s
- B
$2.3 \times 10^{11}$ atoms/s
- C
$4.6 \times 10^{10}$ atoms/s
- ✓
$2.3 \times 10^8$ atoms/s
AnswerCorrect option: D. $2.3 \times 10^8$ atoms/s
(d) $2.3 \times 10^8$ atoms/s
View full question & answer→MCQ 1381 Mark
The decay constant of a radioactive element is $1.5 \times 10^{-9}$ per second. Its mean life in seconds will be
- A
$1.5 \times 10^{9}$
- B
$4.62 \times 10^8$
- ✓
$6.67 \times 10^8$
- D
$10.35 \times 10^8$
AnswerCorrect option: C. $6.67 \times 10^8$
(c) $6.67 \times 10^8$
View full question & answer→MCQ 1391 Mark
In the disintegration series ${ }_{92}^{238} U \xrightarrow{\alpha} X \xrightarrow{\beta^{-}}{ }_{ Z }^{ A _{ Y }}$ The value of Z and A respectively will be
- A
$92,236$
- B
$88,230$
- C
$90,234$
- ✓
$91,234$
AnswerCorrect option: D. $91,234$
(d) $91,234$
View full question & answer→MCQ 1401 Mark
Certain radio-active substance reduces to 25% of its value in 16 days. Its half-life is
MCQ 1411 Mark
1 mg gold undergoes decay with 2.7 days half-life period, amount left after 8.1 days is
MCQ 1421 Mark
99% of a radioactive element will decay between
MCQ 1431 Mark
A radioactive nucleus with Z protons and N neutrons emits an a-particle, 2b-particles and 2 gamma rays. The number of protons and neutrons in the nucleus left after the decay respectively, are
MCQ 1441 Mark
If a radioactive substance reduces to $\frac {1}{16}$ of its original mass in 40 days, what is its half-life
View full question & answer→MCQ 1451 Mark
A radioactive nucleus emits a beta particle. The parent and daughter nuclei are
MCQ 1461 Mark
View full question & answer→MCQ 1471 Mark
During negative b - decay
- ✓
Neutron converts into proton
- B
Proton converts into neutron
- C
Neutron proton ratio increases
- D
AnswerCorrect option: A. Neutron converts into proton
Neutron converts into proton
View full question & answer→MCQ 1481 Mark
When a radioactive substance emits an a -particle, its position in the periodic table is lowered by
MCQ 1491 Mark
The electron emitted in beta radiation originates from
- A
- B
Free electrons existing in nuclei
- ✓
Decay of a neutron in a nucleus
- D
Photon escaping from the nucleus
AnswerCorrect option: C. Decay of a neutron in a nucleus
Decay of a neutron in a nucleus
View full question & answer→MCQ 1501 Mark
In the given nuclear reaction, how many a and b particles are emitted $92^{ X ^{235}} \rightarrow 82^{ Y ^{207}}$
- A
3a particles and 2b particle
- B
4a particles and 3b particle
- C
6a particles and 4b particle
- ✓
7a particles and 4b particle
AnswerCorrect option: D. 7a particles and 4b particle
(d) 7a particles and 4b particle
View full question & answer→