QUIZ 2:Radioactivity And Nuclear Physics(#freetestseries)
15 Questions MCQ Test | QUIZ 2:Radioactivity And Nuclear Physics(#freetestseries)
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The graph between wave number (ν¯) and angular frequency (w) is [AIIMS 2002]
-
ω=2πν=2πc/λ=2πcν¯=
-
ω∝ν¯
.
Binding energy per nucleon plot against the mass number for stable nuclei is shown in the figure. Which curve is correct [Orissa JEE 2002] 
with increase in mass no. stability decreases
Binding energy per nucleon verses mass number curve for nuclei is shown in the figure. W, X, Y and Z are four nuclei indicated on the curve. The process that would release energy is [IIT-JEE 1999] 
- Energy is released in a process when total Binding energy (B.E.) of the nucleus is increased or we can say when total B.E. of products is more than the reactants. By calculation we can see that only in case of option (c), this happens. Given
W→2Y
B.E. of reactants = 120 ´ 75 = 900 MeV and B.E. of products =2×(60×85)=1020MeV
i.e. B.E. of products > B.E. of reactants.
The graph between the instantaneous concentration (N) of a radioactive element and time (t) is
The count rate of 10g of radioactive material was measured at different times and this has been shown in the figure. The half-life of material and the total counts (approximately) in the first half life period, respectively are [CPMT 1986] 
- Read time for 50 count rate, it gives half-life period of 3 hrs, one small square gives 600 counts (10 × 60). The number of small squares between graph and time axis are approx 24 Hence count rate =
24×600=14400
A radioactive material decays b simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is ?
A nucleus at rest breaks into two nuclear parts which have their velocities ratio equal to 8: 1. The ratio of their nuclear radii is .....
1.conserve momentum
2.density is same
Ten grams of 57Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be nearly (in grams)?
the half-life of 24Na is 15.0 h. How long does it take for 80 percent of a sample of this nuclide to decay? [In 5=1.6](in h)
Tritium (31H) has a half-life of 12.5y against beta decay. What fraction of a sample of tritium will remain undecayed after 25y?
N=N0(1/2)n,where n=no. of half lifes
Assertion : Neutrons penetrate matter more readily as compared to protons. Reason : Neutrons are slightly more massive than protons. [AIIMS 2003]
Neutron is about 0.1 more massive than proton. But the unique thing about the neutron is that while it is heavy, it has no charge (it is neutral). This lack of charge gives it the ability to penetrate matter without interacting as quickly as the beta particles or alpha particles.
Assertion : Radioactive nuclei emit β−1 particles. Reason : Electrons exist inside the nucleus. [AIIMS 2003]
Nuclear stability depends upon the ratio of neutron to proton. If the n/p ratio is more than the critical value, then a neutron gets converted into a proton forming a β− particle in the process. n→p+e− The β− particle (e−) is emitted from the nucleus in some radioactive transformation. So electrons do not exist in the nucleus but they result in some nuclear transformation.
Assertion : Density of all the nuclei is same. Reason : Radius of nucleus is directly proportional to the cube root of mass number. [AIIMS 2000]
Assertion : Isobars are the element having same mass number but different atomic number. Reason : Neutrons and protons are present inside nucleus. [AIIMS 1997]
Assertion : The ionising power of b-particle is less compared to a-particles but their penetrating power is more. Reason : The mass of b-particle is less than the mass of a-particle.
b-particles, being emitted with very high speed compared to a-particles, pass very little time near the atoms of the medium. So the probability of the atoms being ionised is comparatively less. But due to this reason, their loss of energy is very slow and they can penetrate the medium through a sufficient depth.
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