QUESTION AND ANSWERS

Chemistry and Physics CET Question Papers

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THE CHEMICAL ELEMENTS SORTED BY NAME IN AN ALPHABETICAL ORDER

Element name	Element symbol	Atomic number
Actinium	Ac	89
Aluminium	Al	13
Americium	Am	95
Antimony	Sb	51
Argon	Ar	18
Arsenic	As	33
Astatine	At	85
Barium	Ba	56
Berkelium	Bk	97
Beryllium	Be	4
Bismuth	Bi	83
Bohrium	Bh	107
Boron	B	5
Bromine	Br	35
Cadmium	Cd	48
Caesium	Cs	55
Calcium	Ca	20
Californium	Cf	98
Carbon	C	6
Cerium	Ce	58
Chlorine	Cl	17
Chromium	Cr	24
Cobalt	Co	27
Copernicium	Cn	112
Copper	Cu	29
Curium	Cm	96
Darmstadtium	Ds	110
Dubnium	Db	105
Dysprosium	Dy	66
Einsteinium	Es	99
Erbium	Er	68
Europium	Eu	63
Fermium	Fm	100
Flerovium	Fl	114
Fluorine	F	9
Francium	Fr	87
Gadolinium	Gd	64
Gallium	Ga	31
Germanium	Ge	32
Gold	Au	79
Hafnium	Hf	72
Hassium	Hs	108
Helium	He	2
Holmium	Ho	67
Hydrogen	H	1
Indium	In	49
Iodine	I	53
Iridium	Ir	77
Iron	Fe	26
Krypton	Kr	36
Lanthanum	La	57
Lawrencium	Lr	103
Lead	Pb	82
Lithium	Li	3
Livermorium	Lv	116
Lutetium	Lu	71
Magnesium	Mg	12
Manganese	Mn	25
Meitnerium	Mt	109
Mendelevium	Md	101
Mercury	Hg	80
Molybdenum	Mo	42
Neodymium	Nd	60
Neon	Ne	10
Neptunium	Np	93
Nickel	Ni	28
Niobium	Nb	41
Nitrogen	N	7
Nobelium	No	102
Osmium	Os	76
Oxygen	O	8
Palladium	Pd	46
Phosphorus	P	15
Platinum	Pt	78
Plutonium	Pu	94
Polonium	Po	84
Potassium	K	19
Praseodymium	Pr	59
Promethium	Pm	61
Protactinium	Pa	91
Radium	Ra	88
Radon	Rn	86
Rhenium	Re	75
Rhodium	Rh	45
Roentgenium	Rg	111
Rubidium	Rb	37
Ruthenium	Ru	44
Rutherfordium	Rf	104
Samarium	Sm	62
Scandium	Sc	21
Seaborgium	Sg	106
Selenium	Se	34
Silicon	Si	14
Silver	Ag	47
Sodium	Na	11
Strontium	Sr	38
Sulfur	S	16
Tantalum	Ta	73
Technetium	Tc	43
Tellurium	Te	52
Terbium	Tb	65
Thallium	Tl	81
Thorium	Th	90
Thulium	Tm	69
Tin	Sn	50
Titanium	Ti	22
Tungsten	W	74
Ununoctium	Uuo	118
Ununpentium	Uup	115
Ununseptium	Uus	117
Ununtrium	Uut	113
Uranium	U	92
Vanadium	V	23
Xenon	Xe	54
Ytterbium	Yb	70
Yttrium	Y	39
Zinc	Zn	30
Zirconium	Zr	40

CHARGE-COUPLED DEVICES (CCD)

A charge-coupled device (CCD) is a kind of device that is widely used for such diverse applications as computer memories and image recording. The charge-coupled device employs an array of metal-oxide contacts, as illustrated in Fig. 14.25. Assuming a p-type semiconductor, each of them has a positive imposed potential to create an inversion layer just inside the semiconductor.

Scattering of electromagnetic waves

The third important phenomenon that affects wave propagation is scattering. Scattering results from what are, effectively, elastic collisions between the photons of the incident beam and particles or heterogeneities in the material, causing the photons to be deflected, or scattered, so that they propagate in some new direction. Scattering subtracts intensity from the transmitted wave and contributes to its attenuation. The material property that governs scattering is called the scattering coefficient, S. A wave that is transmitted through a medium with scattering coefficient, S, is attenuated according to the relation

Optical glass and gemstones

Optical glasses serve a number of different functions. Some, like window glass, are intended to maximize transparency. Others, like "crystal" glassware, are intended both to reveal what is contained and to add a certain luster to it. Still other glasses are colored, often for cosmetic reasons, but sometimes to filter light, as in tinted sunglasses and windshields.

Ferrimagnetism

Ferrimagnetism occurs in polyatomic compounds that contain ions with different core magnetic moments. The core magnetic moments order in an antiferromagnetic pattern, but, since alternate moments differ in magnitude, they do not cancel. The material has a net ferromagnetic moment.

The most important of the ferrimagnetic materials are the ferrites , which have the composition MFe2O4, where M is a divalent metal ion. The most familiar of these is magnetite, Fe3O4, which is the historic lodestone that was the first known ferromagnetic material. The ferrites crystallize in the spinel structure. While I shall not attempt to draw it here, it is a relatively simple structure that has a close-packed, FCC arrangement of oxygen atoms with metal ions in 1/2 of the octahedral interstitial sites and 1/8 of the tetrahedral sites. Since there are 2 tetrahedral and 1 octahedral void per oxygen ion, there are 2 metal ions in octahedral sites for each ion in a tetrahedral site. The magnetic order is an antiferromagnetic order in which the moments of all of the octahedral ions are oriented in one direction, while those of all the tetrahedral ions are oriented in the opposite direction.

What is Magnetostriction

Almost all ferromagnetic materials exhibit the phenomenon of magnetostriction in which the material spontaneously expands or contracts in response to a magnetic field. The phenomenon is due to the fact that the material can ordinarily increase its local magnetization slightly by expanding or contracting to optimize the separation of its ion cores. The sign and magnitude of the magnetostriction depends on the material.

Magnetostriction is a useful property that permits a time-varying magnetic field to be converted to a mechanical signal, or vice versa. It is used in transducers and in small speakers for consumer electronics, among many other applications. While nickel was the principle material of choice for early magnetostrictive devices, ferrites are often preferred today since their high resistance minimizes losses due to induced electrical currents.