Sa-nuclei-solutions.docx

1.) Four nuclei of an element undergo fusion to form a heavier nucleus, with release of energy. Which of the two — the parent or the daughter nucleus — would have higher binding energy per nucleon? Ans. Daughter nuclei B.E. > Parent nuclei B.E. ( stable) (unstable)

2.) (a) Explain the processes of nuclear fission ans nuclear fusion by using the plot of binding energy per nucleon (BE/A) versus the mass number A. Ans. Nuclear Fission : When heavy nucleus bombarded with neutrons & it splits into smaller nucleus & energy released. Ex: 235 1 144 89 1 92 56 36 0 U n Ba Kr 3 n Energy Nuclear Fusion : When 2 smaller nucleus fuse to formed heavy nucleus again energy released. Ex : 2 2 4 112H H He approx.26Mev BE Graph : 1.)

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3.) Asha's mother read an article in the newspaper about a disaster that took place at Chernobyl. She could not understand much from the article and asked a few questions from Asha regarding the article. Asha tried to answer her mother's questions based on what she learnt in Class XII Physics. (a) What was the installation at Chernobyl where the disaster took place ? What, according to you, was the cause of this disaster ? (b) Explain the process of release of energy in the installation at Chernobyl. 1.) (c) What according to you, were the values displayed by Asha and her mother

Ans. Asha's mother read an article in the newspaper about a disaster that took place at Chernobyl. She could not understand much from the article and asked a few questions from Asha regarding the article. Asha tried to answer her mother's questions based on what she learnt in Class XII Physics. (a) What was the installation at Chernobyl where the disaster took place ? What, according to you, was the cause of this disaster ? (b) Explain the process of release of energy in the installation at Chernobyl. (c) What according to you, were the values displayed by Asha and her mother

1.) 4. (a) The figure shows the plot of binding energy (BE) per nucleon as a function of mass number A. The letters A, B, C, D and E represent the positions of typical nuclei on the curve. Point out, giving reasons, the two processes (in terms of A, B, C, D and E ), one of which can occur due to nuclear fission and the other due to nuclear fusion. (3M)(March-15)

(b) Identify the nature of the radioactive radiations emitted in each step of the decay process given below.

And. (a) The nuclei at A and B undergo nuclear fusion as their binding energy per nucleon is small and they are less stable so they fuse with other nuclei to become stable. The nuclei at E undergo nuclear fission as its binding energy per nucleon is less it splits into two or more lighter nuclei and become stable.

5. 6. Why is it found experimentally difficult to detect neutrinos in nuclear -decay ? Solution: Neutrinos are neutral (chargeless), (almost) massless particles that hardly interact with matter. Alternatively The neutrinos can penetrate large quantity of matter withoout any interaction OR Neutrinos are chargeless and (almost) massless particles.

6.) For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour. (4M)(March-14) (a) What, according to you, are the values displayed by Aarti ? (b) How can radioisotopes help a doctor to diagnose brain tumour ? Ans. (a) keen observer/ helpful/ concerned / responsible/ respectful towards elders.(Any two) (b) The doctor can trace and observe, the difference between the movement of an appropriate radio- isotope through a normal brain and a brain having umor in it.