Q21 of 26 Page 1

Define the following terms:

(i) Crystalline solids


(ii) Frenkel defect


(iii) n-type semiconductor


(i) Crystalline solid


• A crystal or a crystalline solid is a material whose atoms or molecules are arranged in an orderly manner and forming a crystal lattice extending in all directions.


• Examples are diamonds, metals and salts.


(ii) Frenkel Defect


• Frenkel defect also called dislocation defect is a point defect found in crystalline solids.


• This defect takes place when an atom or an ion of smaller size leaves it site, creating a vacancy and occupies an interstitial site elsewhere.


(iii) n-type semiconductor


• N-type semiconductor is also called extrinsic semiconductor which is doped with a pentavalent element having 5 electrons in its valence shell.


• The pentavalent impurities that are commonly used are phosphorous, arsenic, antimony or bismuth.


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 23

Mr. Roy the principle of one reputed school organized a seminar in which he invited parents and principals to discuss the serious issue of diabetes and depression in students. They resolved this issue by strictly banning junk foods in schools and introducing healthy snacks and drinks like soup, lassi, milk etc. in the school canteens. They also made compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Roy conducted a health survey in most of the schools and discovered a tremendous improvement in the health of the students.

After reading the above passage, answer the following questions


(i) What are the values (at least 2) displayed by Mr. Roy?


(ii) As a student, how can you spread awareness about this issue?


(iii) What are tranquilizers? Give an example.


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