MEDIUM
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Important Questions on Matter is Everywhere

EASY
An intrinsic semiconductor is converted into n-type extrinsic semiconductor by doping it with:-
EASY
The barrier potential of a p-n junction depends on:
a type of semi-conductor material
b amount of doping
c temperature
Which one of the following is correct?
HARD

The cubic unit cell structure of a compound containing cation M and anion X is shown below. When compared to the anion, the cation has smaller ionic radius. Choose the correct statement(s).

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HARD
Consider an ionic solid MX, with NaCl structure. Construct a new structure Z, whose unit cell is constructed from the unit cell of MX, following the sequential instructions given below. Neglect the charge balance.

(i) Remove all the anions X, except the central one.

(ii) Replace all the face centered cations M, by anions X.

(iii) Remove all the corner cations M.

(iv) Replace the central anion X, with cation M.

The value of number of anionsnumber of cations in Z is _____.
EASY

In the following circuit diagram, the current through the battery is

Question Image

MEDIUM
The contribution to the total current in a semiconductor, due to electrons and holes are 0.75 and 0.25 respectively. The drift velocity of electrons is 32 times that of holes at this temperature. Then the ratio between electron concentration and hole concentration is
EASY
A compound formed by elements X and Y crystallises in the cubic structure, where X atoms are at the corners of a cube and Y atoms are at the centre of the body. The formula of the compounds is
EASY
In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion Ca2+ and fluoride ion F- are
EASY
A unit cell of calcium fluoride has four calcium ions. The number of fluoride ions in the unit cell is
MEDIUM
The graph of lnRR0 versus lnA (R=radius of a nucleus and A=mass number) is
EASY
Which among the following is NOT a polar molecular solid ?
EASY
Among the following, which have highest melting point?
EASY

Match the following

        List - I                                      List-II
A) Metallic solid                         I) Carbon tetrachloride
B) Covalent solid                       II) Calcium fluoride
C) Molecular solid                     III) Copper
D) Ionic solid                             IV) Silicon carbide
                                                   V) Glass

The correct answer is

MEDIUM
The density of an electron-hole pair in pure germanium is 3×1016 m-3 at room temperature. On doping with aluminium, the hole density increases to 4.5×1022 m-3. Now the electron density (in m-3 ) in doped germanium will be
MEDIUM
Which of the following oxides shows electrical properties like metals?
MEDIUM
The radius of K+ is 133 pm and that of Cl- is 181 pm. The volume of the unit cell of KCl expressed in 10-22 cm3 is:
HARD
In a Davisson-Germer experiment, Helium atoms were used in place of electrons. What should be the energy of Helium so that a strong peak of scattered He appears at an angle of 50°, as was the case with electrons having an energy of 54 eV? (Take mass of He atoms to be 7500 times the mass of electrons)
EASY
The mass number and the volume of a nucleus is M and V respectively. If the mass number is increased to 2 M then the volume is changed to