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CBSE Physics (Chapter Wise With Hint / Solution) Class XII

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Atomic Nucleus

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1) what conclusions were drawn from the observation in which few alpha-particle were seen rebounding from gold foil?

2) which observation led to the conclusion in the α-particle scattering exp. That atom has vast empty space?

3) Compare the radii of two nuclei with mass number 1 and 27 respectively.

4) Two nuclei have mass numbers in the ratio 1:8.What is the ratio of their nuclear radii?

5) which have greater ionizing power:α-particles or β-particles?

6) The half life of a radioactive substance in 30 days. What is the time taken for ¾ of its original mass to disintegrate?

7) Why neutrons are considered as ideal particle for nuclear reactions?

8) Does the ratio of neutrons and protons in the nucleus increase, decreases or remain the same after the emission of ά – particles?

9) Why is the ionization power of ά – particle of greater than γ – rays?

10) A radio isotope of silver has a half life of 20 minutes. What fraction of the original mass would remain after one hour?

11) What changes takes place in the nucleus when a γ – rays is emitted?

12) Can a single nucleus emit ά – particle, β – particle and a γ – rays together?

13) Two nuclei have mass no. in the ratio 1:2. What is the ratio their nuclear densities?

14) Establish the relationship between half life of a radio- active substance and decay constant.

15) Explain how ά particle scattering experiment led to Rutherford to estimate the size of the nucleus.

16) The activity of a radio active material drops to 1-16th of its initial value in 30 days. Find its half life.

17) In a particular fission reaction, a U 235 nucleus captures a slow neutron. The fission products are 3 neutrons, a La 142 and fission products X y z .What is the value of Y and Z.

18) You are given two nuclides Xb) Which one of the two is likely to be more stable? Give reason.

19) A certain radio active substance has a half life of 30 days. What is the disintegration constant? Find its average life.

20) Find the time required to decay 3/4th of a radioactive sample whose half life is 60 days.

21) Neon -23 decays in the following way 23Ne10 ---------------23Ne10 + 0e-1 +γ Find the minimum and maximum kinetic energy that the β-particle can have.

The atomic masses of 23Ne10 and 23Ne10 are 22.99454 and 22.98984 respectively.

22) The disintegration rate of a certain radioactive sample at any instant is 4750 disintegrations per minute. Five minutes later the rate becomes 2700 per minute. Calculate a) Decay constant b) Half-life of the sample

23) Explain with an example, whether neutron-proton ratio increases or decreases during beta decay.

24) The half life period of radioactive element A is the same as the mean half time of another radioactive element B.Initially both of them have the same number of atoms. The radioactive element B decays faster than A. Explain why?

25) Obtain the binding energy of a nitrogen nucleus from the following data mh=1.007834; mn=1.00867; mN=14.03074 Give your answer in MeV.

26) Write nuclear equations for
a) The α-decay of 226Ra88
b) The β- -decay of 32P15
c) The β+ decay of32P15

27) A neutron is absorbed by a 6Li3 nucleus with the subsequent emission of an alpha particle.
i) Write the corresponding nuclear reactions.
ii) Calculate the energy released in MeV, in this reaction.
Given mass 6Li3=6.0151264; mass (neutron) =1.00966544
Mass (alpha particle)=4.00260444 and mass(triton)=3.01000004


CBSE Physics (Chapter Wise With Hint / Solution) Class XII (By Mr. Sreekumaran Nair)