physics [simple facts in physics]

1. Mechanics
2. 1. Weight (force of gravity) decreases as you move away from the earth by distance squared.
   2. Mass and inertia are the same thing.
   3. Constant velocity and zero velocity means the net force is zero and acceleration is zero.
   4. Weight (in newtons) is mass x acceleration (w = mg). Mass is not weight!
   5. Velocity, displacement [s], momentum, force and acceleration are vectors.
   6. Speed, distance [d], time, and energy (joules) are scalar quantities.
   7. The slope of the velocity-time graph is acceleration.
   8. At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the difference to the sum is the total range of possible resultants.
   9. Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle.
   10. An unbalanced force (object not in equilibrium) must produce acceleration.
   11. The slope of the distance-tine graph is velocity.
   12. The equilibrant force is equal in magnitude but opposite in direction to the resultant vector.
   13. Momentum is conserved in all collision systems.
   14. Magnitude is a term use to state how large a vector quantity is.
3. 1. Energy
4. 1. 
      
   2. Mechanical energy is the sum of the potential and kinetic energy.
   3. Units: a = [m/sec²], F = [kg?m/sec²] (newton), work = pe= ke = [kg?m²/sec²] (joule)
   4. An ev is an energy unit equal to 1.6 x 10^-19 joules
   5. Gravitational potential energy increases as height increases.
   6. Kinetic energy changes only if velocity changes.
   7. Mechanical energy (pe + ke) does not change for a free falling mass or a swinging pendulum. (when ignoring air friction)
   8. The units for power are [joules/sec] or the rate of change of energy.
5. 1. Electricity
6. 1. 
      
   2. A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].
   3. Short fat cold wires make the best conductors.
   4. Electrons and protons have equal amounts of charge (1.6 x 10^-19 coulombs each).
   5. Adding a resistor in parallel decreases the total resistance of a circuit.
   6. Adding a resistor in series increases the total resistance of a circuit.
   7. All resistors in series have equal current (I).
   8. All resistors in parallel have equal voltage (V).
   9. If two charged spheres touch each other add the charges and divide by two to find the final charge on each sphere.
   10. Insulators contain no free electrons.
   11. Ionized gases conduct electric current using positive ions, negative ions and electrons.
   12. Electric fields all point in the direction of the force on a positive test charge.
   13. Electric fields between two parallel plates are uniform in strength except at the edges.
   14. Millikan determined the charge on a single electron using his famous oil-drop experiment.
   15. All charge changes result from the movement of electrons not protons (an object becomes positive by losing electrons)
7. 1. Magnetism
8. 1. 
      
   2. The direction of a magnetic field is defined by the direction a compass needle points.
   3. Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
   4. Magnetic flux is measured in webers.
   5. Left hands are for negative charges and right hands are for positive charges.
   6. The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant.
   7. Solenoids are stronger with more current or more wire turns or adding a soft iron core.
9. 1. Wave Phenomena
10. 1. 
       
    2. Sound waves are longitudinal and mechanical.
    3. Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
    4. All angles in wave theory problems are measured to the normal.
    5. Blue light has more energy. A shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
    6. The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest.
    7. A prism produces a rainbow from white light by dispersion (red bends the least because it slows the least).
    8. Light wave are transverse (they can be polarized).
    9. The speed of all types of electromagnetic waves is 3.0 x 10⁸ m/sec in a vacuum.
    10. The amplitude of a sound wave determines its energy.
    11. Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase.
    12. At the critical angle a wave will be refracted to 90 degrees.
    13. According to the Doppler effect a wave source moving toward you will generate waves with a shorter wavelength and higher frequency.
    14. Double slit diffraction works because of diffraction and interference.
    15. Single slit diffraction produces a much wider central maximum than double slit.
    16. Diffuse reflection occurs from dull surfaces while regular reflection occurs from mirror type surfaces.
    17. As the frequency of a wave increases its energy increases and its wavelength decreases.
    18. Transverse wave particles vibrate back and forth perpendicular to the wave direction.
    19. Wave behavior is proven by diffraction, interference and the polarization of light.
    20. Shorter waves with higher frequencies have shorter periods.
    21. Radiowaves are electromagnetic and travel at the speed of light (c).
    22. Monochromatic light has one frequency.
    23. Coherent light waves are all in phase.
11. 1. Geometric Optics
12. 1. 
       
    2. Real images are always inverted.
    3. Virtual images are always upright.
    4. Diverging lens (concave) produce only small virtual images.
    5. Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium {frequency remains constant}.
    6. The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red.
13. 1. Modern Physics
14. 1. 
       
    2. The particle behavior of light is proven by the photoelectric effect.
    3. A photon is a particle of light {wave packet}.
    4. Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave. (DeBroglie Waves)
    5. All electromagnetic waves originate from accelerating charged particles.
    6. The frequency of a light wave determines its energy (E = hf).
    7. The lowest energy state of a atom is called the ground state.
    8. Increasing light frequency increases the kinetic energy of the emitted photo-electrons.
    9. As the threshold frequency increase for a photo-cell (photo emissive material) the work function also increases.
    10. Increasing light intensity increases the number of emitted photo-electrons but not their KE.
15. 1. Internal Energy
16. 1. 
       
    2. Internal energy is the sum of temperature (ke) and phase (pe) conditions.
    3. Steam and liquid water molecules at 100 degrees have equal kinetic energies.
    4. Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
    5. Temperature measures the average kinetic energy of the molecules.
    6. Phase changes are due to potential energy changes.
    7. Internal energy always flows from an object at higher temperature to one of lower temperature.
17. 1. Nuclear Physics
18. 1. 
       
    2. Alpha particles are the same as helium nuclei and have the symbol .
    3. The atomic number is equal to the number of protons (2 for alpha)
    4. Deuterium () is an isotope of hydrogen ()
    5. The number of nucleons is equal to protons + neutrons (4 for alpha)
    6. Only charged particles can be accelerated in a particle accelerator such as a cyclotron or Van Der Graaf generator.
    7. Natural radiation is alpha (), beta () and gamma (high energy x-rays)
    8. A loss of a beta particle results in an increase in atomic number.
    9. All nuclei weigh less than their parts. This mass defect is converted into binding energy. (E=mc²)
    10. Isotopes have different neutron numbers and atomic masses but the same number of protons (atomic numbers).
    11. Geiger counters, photographic plates, cloud and bubble chambers are all used to detect or observe radiation.
    12. Rutherford discovered the positive nucleus using his famous gold-foil experiment.
    13. Fusion requires that hydrogen be combined to make helium.
    14. Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons.
    15. Radioactive half-lives can not be changed by heat or pressure.
    16. One AMU of mass is equal to 931 meV of energy (E = mc²).
    17. Nuclear forces are strong and short ranged.
19. 1. General
20. 1. 
       
    2. The most important formulas in the physics regents are:
       
    3. Physics is fun. (Honest!)

chemistry [solid state]

A solid is defined as that form of matter which possesses rigidity and due to which possesses a definite volume and a definite shape. � The solids can be classified into - (a) Amorphous solids (b) Crystalline solids The solids which do not have any definite shape geometrically are called AMORPHOUS (Morpha = form) solids. Infact these have a random and disordered arrangement of atoms. These solids are also called �super cooled liquids� and are without sharp melting points i.e., these have �short range order� of their constituent atoms like that in the liquids. e.g. Glass, Rubber, Plastics etc. Amorphous solids are isotropic i.e., their physical properties are same in all directions. Actually, here the particles are randomly arranged and disordered due to which all directions are equivalent hence all the properties remain same in all directions. A crystal is a solid which is composed of atoms arranged in an orderly repetitive array i.e., A homogeneous anisotropic substance having a definite geometrical shape with surfaces that are usually plane with sharp edges. In many solids, we may not clearly see the shape of crystals, because several small or micro-sized crystals are tightly packed together without any specific order. Such a substance which is infact crystalline but is superfine to be seen as crystals is called MICRO-CRYSTALLINE or POLYCRYSTALLINE SOLID. e.g. many metals and alloys. A copper wire have microcystalline structure. On the basic of nature of bonding, the crystallien solids have been classified into following 4 types IONIC CRYSTALS : With (+) ve and ( - ) ve ions as constituent particles (which are bonded together by strong electrostatic MOLECULAR CRYSTALS : With molecules as constituent particles (bonded by vander Waals�forces). For Example : I2 ,Dry Ice (Solid CO2), Solid CH4 Ice etc. COVALENT CRYSTALS : With atoms as constitutent particles (bonded together by coralent bonds) For Example : Diamond, Graphite, Silicon etc. METALLIC CRYSTALS : With positive metal ions (Kernels) and free electrons as constituent particle (bonded together by metallic bonds) For Example : All Metals and alloys. The external features of a crystals include - 1. Faces, 2. Forms 3. Edge 4. Solid angle 5. Interfacial angle 6. Zone and Zone-axis The crystals are bounded by surfaces which are usually planer and arranged in definite pattern. These surfaces are called faces. Faces are of two types namely like and unlike faces. The crystals with all similar surfaces is said to have like faces e.g. Alums, fluorspar etc. while galena crystal have unlike faces i.e., if have a combination of cubical and octohedral faces. All the faces corresponding to a crystal are said to constitute a form. The forms may be SIMPLE (with like faces) or in COMBINATION (with unlike faces). In a crystal, when two adjacent faces intersect, we get an edge and when three or more edges intersect we get a SOLID ANGLE. The angle between the normals to the two intersecting faces is called an interfacial angle. (i) AB type structures (ii) AB2 or A2B type structures. The AB type structures designate equality in no. of cations and the no. of anions. The examples of this type of structes include - NaCl with coordination No. 6 - 6, CsCl with coordination no. 8 - 8 and ZnS with coordination no. 4 - 4. The AB2 or A2B type of ionic crystals contain the ions in the ratio 1:2 or 2 : 1 respectively. For Example : CaF2 populary called to have fluorite structure with other examples like SrF2, BaF2, PbF2and BaCl2 etc. The coordination number of Ca++ in CaF2 is 8 while that of F- is 4. On the contrary Na2O have antifluorite structure i.e., here the place of cations in occupied by anions and vice versa. The size of the unit cell and arrangement of atoms in a crystal is determined with the help of measurement of differaction of x-rays by the crystal. When a beam of monochromatic x-ray strikes two planes of atoms in a crystal at a certain angle Q, It is reflected. The intensity of reflected beam will be maximum if - In actual practice it is difficult to grow a perfect crystal. Even single crystals grown with-all care are found to contain many internal irregularities. These irregularities are called crystal defects and can be defined as “Any departure from perfectly ordered arrangement of atoms in a crystal in called IMPERFECTION or DEFFECT”.These imperfections not only modify the properties but also sometimes impart new properties to the solids. In an ionic crystal, the electrons are mostly concentrated around the electronegative component. Some of these electrons have the tendency of thermal release i.e., the property of loosing its position on increase in temperature. These thermally released electrous become mobile resulting to increase in conductivity of solid When an electron is thermally removed from its position the electron deficient site thus formed is called a HOLE. Holes also impart electrical conductivity but their movement is opposite in direction to which the electrons move. The electrons and holes in solids give rise to electronic imperfections. The defect discussed above is/are called point defects and can be categorised to following 3 types - (A) Stoichiometric defects (B) Non - stoichiometric defects (C) Impurity defects. If imperfections in crystals are such that the ratio between the cations and the anions remains the same as described in its molecular formula, the defect will be called STOICHIOMETRIC DEFECT. These can be further categorised to- (a) Schottky defect (b) Frenkel defect. In an ionic crystal of A+B- type, if equal no. of cations and anions are missing from their lattice sites, the defect is called SCHOTTKY DEFECT. In this defect electrical neutrality is maintained due to disappearence of similar no. of cations and anions (Lattice Vacancy). The schottky defect is shown by highly ionic compounds having - (i) High co-ordination number (ii) Small difference in the size of cations and anions For Example : NaCl, KCl, KBr, CsCl etc. Due to such a defect density of the solid decreases. In an ionic crystal when an ion is missing from its lattice site (causing a hole or vacancy there) and occupies interstitial site the defect is called FRENKEL’S DEFECT. In this defect the electrical neutrality and stoichiometry of the compound is maintained as ion does not leave the crystal completely. This type of defect is seen in those crystals where the difference in the size of cations and anions is very large and their coordination no. is low for example AgCl, AgBr, ZnS etc. Due to such a defect the density of the solid remains unchanged. When the ratio of cations and anions due to imperfection differ from that indicated by their molecular formula, the defects are called Non-stoichiometric defects. These defects results in either excess of metal atom of excess of non metal atom. The metal excess may occur in either of the following two ways - (i) Due to missing of a negative ion from its lattice site, thus leaving a hole which is occupied by an electron. The electrons thus trapped in the anion vacancies are called F.Centres (F=Farbe=German word for color) as these are responsible for imparting color to the crystals. This defect is similar to frenkel defect Metal defeciency or Non metal excess occurs where the metal shows variable valency i.e., transition metals. The defect usually occur due to missing of a cation from its lattice site and presence of the cation having higher charge at different lattice site thus balancing the loss. e.g. FeO, FeS, NiO etc. Another common method of introducing defects in ionic solids is by adding impurity ions having different change than host ion. These foreign atoms are present at lattice site in substitutional solids and at vacant interstitial sites in interstitial solids. The faces, edges and interfacial angles are related as f + C = e + 2 where, f = Number of faces e = Number of edges c = Number of interfacial angles. The faces of a crystal occur in sets. These sets are called ZONES. Each zone forms a complete belt around a crystals. A line drawn through the centre of a crystal in a direction parallel to the edges of a zone is known as ZONE AXIS. Some other terms related with solids include 1.Unit cell and space Lattice 2. Coordination Number 3. Crystallographic axes 4. Standard or unit plane 5. Axial ratio. The regular arrangement of the constituent particles of a crystalline solid in the 3 dimensional space is called the space lattice or crystal lattice. The smallest portion of the complete space which when repeated again and again in different directions produces the complete space lattice, is called the unit cell. The unit cells are of the following 2 types - 1. Simple or primitive unit cell. 2. Non primitive or multiple unit cell. The simplest unit cell which has the lattice points at the corners or in the other words we can say when particles are present only at the corners of the unit cell. It is denoted by P. When a unit cell contains more than one additional lattice point (additional to those defined in simple unit cell) it is called non-premitive or multiple unit cell. It is further sub divided into - (i) Face centred unit cell (F) (ii) End face centred unit cell (C) (iii) Body centred unit cell (I) When there particles or lattice points are present at the centre of each face in addition to particles at the corner the unit cell is called FACE CENTERED. When in the unit cell, besides the points or particles at the corner of cell, the points or particles are located at the centre of any two parallel faces of the unit cell, it is called side - centred or end face unit cell. In a unit cell when, beside the points or particles at the corner there is one particle located at the centre within its body, it is called body centred arrangement and the unit cell is called body centred unit cell. The geometry of a crystal can be best described in terms of 3 non-coplaner coordinate axes, called CRYSTALLOGRAPHIC AXES. These axes, namely X,Y and Z, may be mutually at right angles to each other or may be inclined to each other at different angles. As per convention the angle between Y and Z axes is called a, between Z and X is called b and between X and Y is called g. On the basis of different possible values of a, b and g and different axial distances or edge lengths a, b and c following 7 types of 3 dimensinal primitive cells or crystal systems are given - 1. Cubic : Where a = b = c & a = b = g = 90� for Example NaCl, KCl Diamond, Copper, Zinc blende etc. 2. Tetragonal : Where a = b c and a = b = g = 90� For Example : Canssiterite (SnO2), white Tin, T1O2 (Rutile) etc. 3. Orthorhombic : Where a b c and `a = b = g =90�. (Rhombic) For Example : Rhombic Sulfur, BaSO4 (Baryta) CaCO3, PbCO3 (cerrusite) etc. 4. Monoclinic : Where a b � c and a = g = 90�, b 90� For Example : Monoclinic sulfer, PbCrO2 etc. 5. Hexagonal : Where a = b � c and a = b = 90�, g = 120 For Example : Mg, Beryl, ZnO (Zincite) PbI2, Graphite etc. 6. Rhombohedral : Where a = b = c and a = b = g� 90� (Trigonal) For Example : NaNO3,CaCO3(Calcite) MgS(Cinnabar) etc. 7. Triclinic : Where a� b� c and a b g � 90� For Example: K2Cr2O77,H3BO3,CuSO4,5H2O etc. As there are 5 possible 2 dimensional lattice, similarly there are only 14 possible 3 dimensional lattices. These are called Bravais lattices (after the French Mathematician who first described them). In different types of unit cells, the no. of atoms per unit cell can be calculated as follows : (a) In Primitive or Simple cubic unit cell - from the above figure it is clear that here eight atoms which are present at 8 corners are shared by 8 unit cells. Hence, contribution of each atom present at the corner = Thus, total no. of atoms present per unit cell = 8 x = 1atom (b) In body centred cubic unit cell. from the above figure it is clear that this unit cell has 1 complete atom additional to that present in simple cubic unit . Hence, the total no. of atom present = 1+1=2 atoms per unit cell. (c) In face centred cubic unit cell : s From the above figure it is clear that here - (i) 8 corner atoms x atoms per unit cell = 1 atom (ii) 6 face atoms with representation of 1/2 atom per face per unit cell, thus - 6x1/2 = 3 atoms Total atoms present per unit cell = 1+3 = 4 atoms (d) In end face centred cubic unit cell : Similarly end face centred cubic unit cell have 1 instead of 3 face atoms present in face centred cubic unit cell. Rest distribution is same (because here only 2 parallel face have one atom each at the centre of face shared by two unit cells). Thus, the total no. of atoms present per unit cell here is = 1 + 1 = 2 atoms per unit cell. If we represent atoms by sphere, the no. of sheres surrounding a particular sphere is called the co-ordination number of that sphere i.e., in simple words it is the no. of atoms or ions or molecules surrounding a particular atom in a crystal lattice. Any face of the crystal may cut into one or more crystallographic axes. The face which cuts all the three axes in called STANDARD or UNIT PLANE. The distances of the points where the standard plane cuts the three axes from the origin are called intercepts. The intercepts a,b and c and axis x, y and 2 respectively are called CRYSTAL PARAMETERS. The actual practice the ratio a : b : c is called the AXIAL RATIO and it depends upon the point where all the three axes meet. To understand the packing of particles in a crystal it is assumed that these particles are hard spheres of identical size. This packing can be seen in one of the following ways- (a) The simplest way is if spheres are placed in a horizontal row, touching each other as seen below - Thus an edge of crystal is formed. (b) When the above written rows combine, 2 type of combinations are possible - (i) With a horizontal as well as vertical alignment as shown below - Thus particles form square and the packing is called Square close packing. The empty space between the the partivles in a close packing is called a VOID as seen above.

Chapterwise distribution of questions IN VIT 2008

CHAPTERWISE ANALYSIS VITEEE 2008 - MATHEMATICS
TOPICS	Easy	Medium	Difficult	Total Marks	% of Marks
ALGEBRA	9	5	1	15	38%
Theory of Equations	1	1		2	5%
Sequences & Series	1			1	3%
Complex Numbers	1	1		2	5%
Permutations & Combinations		1		1	3%
Theory of Probability & Statistics	4	1		5	13%
Matrices & Determinants	2	1	1	4	10%
ANALYTICAL GEOMETRY	2			2	5%
DIFFERENTIAL CALCULUS	3	2	1	6	15%
TRIGONOMETRY	1	1	0	2	5%
Trigonometric Functions, Inverse trig.func., Trig.Equations	1			1	3%
Properties of Triangles		1		1	3%
VECTORS, 3-D, MATRICES & DETERMINANTS	3	3		6	15%
INTEGRAL CALCULUS	0	3	5	8	20%
Integral Calculus		1	3	4	10%
Differential Equations		2	2	4	10%
DISCRETE MATHEMATICS	1			1	3%
	19	14	7	40	1

Chapterwise distribution of questions IN VIT 2008

CHAPTERWISE DISTRIBUTION OF QUESTIONS FOR PHYSICS

Sl.No.	Chapter Name	No. of Questions	Difficulty Level
			No. of E	No. of M	No. of D
1	Electrostatics	7	3	3	1
2	Current Electricity	6	4	2
3	Magnetic Effects of Current
4	Magnetism
5	EMI & AC	4	4
6	Ray Optics	2	2
7	Wave Optics	4	2	1	1
8	Modern Physics	8	5	3
9	Electronics	6	5		1
10	Communications	2	2

PART – 1 [PHYSICS]

1. In nature, the electric charge of any system is always–

Ans: Quantisation of charge

Choice (D)

2. The energy stored in the capacitor as shown in Fig. (a) is 4.5 ´ 10^{- 6} J. If the battery is replaced by –

Ans:

= 4.5 ´ 10^{- 6} J

Choice (B)

3. Equal amounts of a metal are converted into cylindrical wires of different lengths (L) and cross-sectional –

Ans: R =

Choice (C)

4. If the force exerted by an electric dipole on a charge q at a distance of 1 m is F, the force–

Ans:

Choice (D)

5. A solid sphere of radius R ₁ and volume charge density r = is enclosed by a hollow sphere of radius R₂ with negative surface charge density–

Ans: Q _in =

=

= 4p R₂²s

Choice (C)

6. A solid spherical conductor of radius R has a spherical cavity of radius a9a <> charge +Q is kept at the center.–

Q

-Q

+Q

Ans:

Choice (B)

7. A cylindrical capacitor has charge Q and length L. If both –

Ans: U ₁ =

U ₂ =

Choice (B)

8. Three resistances of 4 W each are connected as shown in figure. If the point D divides the resistance –

2

4

2

4

Ans:

Choice (C)

9. The resistance of a metal increases with increasing –

Ans: Vibration of lattice ions increases with

temperature

Choice (B)

10. In the absence of applied potential, the electric current flowing through-

Ans: Thermal velocity of electrons is in random

directions

Choice (C)

11. A meter bridge is used to determine the resistance of an unknown wire by measuring the balance point length l. If the wire is replaced by –

Ans:

12. Identify the INCORRECT statement regarding –

Ans: Supercurrent always flows on the surface

of the superconductor

Choice (B)

13. A sample of HCl gas is placed in an electric field of 3 ´ 10⁴ NC^{- 1}. The dipole moment of each HCl molecule is –

Ans: t = pE

Choice (C)

14. When a metallic plate swings between the –

Ans: Lenz’s law

Choice (C)

15. When an electrical appliance is switched on, it responds almost-

Ans: Electromagnetic waves travel with the

speed of light

Choice (B)

16. Two identical incandescent light bulbs are connected as shown in the figure. When the circuit is an AC voltage source–

Ans: At resonance X_L = X_C

Choice (B)

17. A transformer rated at 10 kW is used to connect a 5 kV transmission line to a 240 V circuit. The ratio –

Ans: n =

Choice (B)

18. Three solenoid coils of same dimension, same number of turns and same number of layers of winding are taken. Coil 1 with inductance L₁ was wound using a Mn wire of resistance 11 W / m; –

Ans: Alternate winding in opposite direction

total flux = 0

Choice (C)

19. Light travels with a speed of 2 ´ 10⁸ m/s in crown glass of refractive index 1.5. What is the speed of light –

Ans: n ₁v₁ = n₂v₂

Choice (B)

20. A parallel beam of fast moving electrons is incident normally on a narrow slit. A screen is placed at a large distance from the slit.–

Ans: sinq =

Choice (C)

21. Two beams of light will not give rise to an –

Ans: Since the polarization vectors are

perpendicular their vector sum ¹ 0

Choice (C)

22. A slit of width `a’ is illuminated with a monochromatic light of wavelength l from a distant source and the diffraction pattern –

Ans: sinq =

Choice (B)

23. A thin film of soap solution (n = 1.4) lies on the top of a glass plate (n = 1.5). When visible light is incident almost normal to the plate, two adjacent reflection –

Ans: n ₁l ₁ = n₂l ₂

2n ₁ = 3n₂

Þ n₁ = 3

d = = 450

Choice (B)

24. If the speed of a wave doubles as it passes from shallow water into deeper water, –

Ans: c = fl

Choice (C)

25. A light whose frequency is equal to 6 ´ 10¹⁴ Hz is incident on a metal whose work function is
2 eV –

Ans: hu = f + K.E

Choice (C)

26. An electron microscope is used to probe the atomic arrangements to a resolution of . What should be the electric potential –

Ans:

Choice (D)

27. Which phenomenon best supports the theory that matter –

Ans: Electrons behave also as waves of l =

Choice (B)

28. The radioactivity of a certain material drops to of the initial value in 2 hours. The half –

Ans: Activity changes from A₀ to A₀/16 implies 4 half-lives.

Choice (C)

29. An observer `A’ sees an asteroid with a radioactive element moving by at a speed = 0.3 c and measures the radioactivity decay time to be T<sub>A</sub>. Another observer `B’ –

Ans: Moving clocks are slower T_B <>A

Choice (A)

30. ²³⁴U has 92 protons and 234 nucleons total in its nucleus. It decays by emitting an alpha –

Ans: ²³⁴U₉₂ à ²³⁰Th₉₀ + a

Choice (C)

31. K_a and K_b x-rays are emitted when there is a transition of electron –

Ans: K series end in n = 1

Choice (A)

32. A certain radioactive material _ZX^A starts emitting a and b particles successively such that the end product –

Ans: _ZX^A à _{Z- 3}Y^{A- 8} + 2a + 1b

Choice (B)

33. In the circuit shown above, an input of 1 V is fed into the inverting input of an ideal Op-amp A. The output signal –

Ans: = - 10 (negative feedback)

Choice (B)

34. When a solid with a band gap has a donor level just below its empty energy band, -

Ans: Knowledge based

Choice (D)

35. A p – n junction has acceptor impurity concentration of 10¹⁷ cm^{- 3} in the P side and donor impurity concentration of 10¹⁶ cm^{- 3} in the N side. What is the contact potential at the –

Ans: V _contact =

Choice (A)

36. A zener diode has a contact potential of 1 V in the absence of biasing. It undergoes zener breakdown for an electric field of 10⁶ V/m at the depletion region of p-n junction. If the width –

Ans: V = Ed

Choice (B)

37. In Colpitt oscillator the feedback network –

Ans: a-c equivalent circuit.

Choice (B)

38. The reverse saturation of p-n diode

Ans: Knowledge based

Choice (D)

39. A radio station has two channels. One is AM at 1020 kHz and the other FM at 89.5 MHz. –

Ans: Knowledge based

Choice (A)

40. The communication using optical fibers is –

Ans: Optic fibre uses T.I.R.

Choice (A)