KPK Board 10th Class Physics Ch 9 Nuclear physics Short Questions Answers

Ans.    Protium  (a stable isotope of hydrogen) has same atomic number and mass number, equal to 1.

Explanation:          Hydrogen is the 1^st element in periodic table having three isotopes, protium   deuterium  and Tritium. Protium has one proton inside the nucleus and no neutron. Therefore, its atomic number as well as mass number is equal to one.

β- particle is more likely to expose a film kept in a cardboard box as α- particle can easily be blocked by a paper and cannot penetrate cardboard.

Explanation:           Penetration power of  β- particles is greater than that of α- particles that is why β- particles can easily penetrate through a cardboard. A film kept inside the cardboard will be affected by the  β- particles easily.

Ans.         No, it is not possible for any form of hydrogen to decay by emitting an alpha particle.

Explanation:             Hydrogen is the 1^st element in periodic table having three isotopes, Protium ¹H( having only one proton ionside nucleus), deuterium ²H (having one proton and one neutron inside nucleus) and Tritium ³H (having on proton and two neutrons inside nucleus). Whereas, an alpha particle is composed of two protons and two neutrons. That is why it is not  possible for any isotope (form) of Hydrogen to decay by emitting an alpha particle.

Ans.        They have similar chemical properties because isotopes of an element have the same number of electrons as an atom of that element.

Explanation:             The element arrangement is the same owing to same chemical properties. However, they have different number determines the physical properties such boiling / melting / density etc.

After two half-lives,3⁄4 of a radioactive sample has been decayed.

Explanation: After 1^st half-life, half of the sample will be decayed whereas, half will be left. After 2^nd half-life, another half of the half (i.e. 1⁄2of 1⁄2) will be decayed( i.e. 1⁄4 will be decayed in 2nd half-life and 1⁄4will be left in total).

Ans.    All biologic organisms contain a given concentration of carbon-14; we can use this information to help solve questions about when the organism died. When an organism dies it has a specific ratio by mass of carbon-14 to carbon -12 incorporated in the cells of its body.  (The same ratio as in the atmosphere.) At the moment of death, no new carbon-14 containing molecules are metabolized; therefore, the ratio is at a maximum.  After death, the carbon-14 to carbon-12 ratio begins to decrease because carbon-14 is decaying away at a constant and predicable rate. Remembering that the half-life of carbon-14 is 5700 years, then after 5700 years half as much carbon-14 remains within the organism.

Ans.   There is a common misconception that irradiated food is radioactive.  The radiation used to process foods is very different from the radioactive fallout that occurs after, for example, a nuclear accident. In food processing, the radioactive sources permitted do not generate gamma, electrons or x-rays of sufficient high energy to make food radioactive. No radioactive energy remains in the food after treatment.  The World Health Organization (WHO), the American Dietetic association and the Scientific Committee of the European Union are three internationally recognized bodies that support food irradiation.

Ans.      Alpha particles are the least dangerous in terms of external exposure. Each particle contains a pair of neutrons and a pair of protons. They don’t penetrate very deeply in the skin, if at all – in fact, clothing can stop alpha particles. Unfortunately, alpha particles can be inhaled or ingested, usually in  the form of radon gas.  Once ingested, alpha particles can be very dangerous.  However, even then they don’t typically cause radiation sickness—instead, they lead to lung cancer.

Ans.         Nuclear medicine pharmaceuticals give off gamma rays and particles that allow us to track the radioactive pharmaceuticals within body. The scanners themselves do not create radiation .Very small amounts are used for imaging scans. The radiation disappears (decays) in a very short time due to which it is not harmful for humans. Larger amount are used for therapy but in that case the radiation is targeted very precisely at the cancer cells in order to kill them. For effective doses from nuclear medicine procedures, only one-twentieth of a percent (0.05%) of the patients who have a test may develop a fatal cancer sometime later in life.