Solid State Tes...

Schottky defect is observed in crystals when

Which of the following statements are not true?

(i)  Vacancy defect results in a decrease in the density of the substance.

(ii)  Interstitial defects results in an increase in the density of the substance.

(iii)  Impurity defect has no effect on the density of the substance.

(iv)  Frankel defect results in an increase in the density of the substance.

Which of the following statements are true about metals?

(i)  Valence band overlaps with conduction band.

(ii)  The gap between valence band and conduction band is negligible.

(iii)  The gap between valence band and conduction band cannot be determined.

(iv)  Valence band may remain partially filled.

Match the items given in Column I with the items given in Column II.

Amorphous solid can also be called .............

(i)  Pseudo solids

(ii)  True solids

(iii)  Super cooled liquids

(iv) Super cooled solids

Assertion : Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four.

Reason : Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.

Assertion : The packing efficiency is maximum for the fcc structure.

Reason : The cordination number is 12 in fcc structures. 

Under the influence of electric field, which of the following statements is true about the movement of electrons and holes in a p-type semi conductor?

(i)  Electron will move towards the positvely charged plate through electron holes.

(ii)  Holes will appear to be moving towards the negatively charged plate.

(iii)  Both electrons and holes appear to move towards the positively charged plate.

(iv)  Movement of electrons is not related to the movement of holes.