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Class 12 Physics Question Answers

Question Answer

Class 12

Physics

Master Class 12 Physics: Engag...

Class 12 Physics Question Answers

Describe the experiment to compare the e.m.f. of two cells using potentiometer under the following points:(i). Labeled circuit diagram(ii). Derivation of formula(iii). Observation table(iv). Two precautions.

The power of plane mirror is ___________________A. \\[0\\]B. \\[\\infty \\]C. \\[2{\\text{D}}\\]D. \\[{\\text{4D}}\\]

What is meant by refraction of light? State the laws of reflection.

A point object is placed midway between two plane mirrors at distance ‘a’ apart. The plane mirror forms an infinite number of images due to multiple reflections. The distance between the first two images formed behind any mirror is:$\\left( A \\right)$ a$\\left( B \\right)$ 2a$\\left( C \\right)$ a\/2$\\left( D \\right)$ 4a

Define Modulation. Mention the basic methods of Modulation.

The force between two charged bodies is calledA.) muscular forceB.) gravitational forceC.) magnetic force D.) electrostatic force

A lens produces a virtual image between the object and the lens.A.) Name the lens.B.) Draw a ray diagram to show the formation of this image.

Which of the following is\/ are the advantages of satellite communication?A.) Mobile communication can be easily established by satellite communicationB.) Satellite communication is economical compared with terrestrial communication particularly where long distances are involvedC.) User has control over their own networkD.) All of the above

What will be the frequency of an alternating current if its direction changes after every 0.01s?$\\left( A \\right)20$ Hz.$\\left( B \\right)10$ Hz.$\\left( C \\right)$ 15 Hz.$\\left( D \\right)$ 50 Hz.

The dimension of resistance $R$ in terms of ${\\mu _o}$ and ${\\varepsilon _o}$ are:A.) $\\sqrt {\\dfrac{{{\\mu _o}}}{{{\\varepsilon _o}}}} $B.) $\\sqrt {\\dfrac{{{\\varepsilon _o}}}{{{\\mu _o}}}} $C.) $\\dfrac{{{\\varepsilon _o}}}{{{\\mu _o}}}$D.) $\\dfrac{{{\\mu _o}}}{{{\\varepsilon _o}}}$

The Dimensional formula for the electric field is………………………………….. $(a){\\text{ }}\\left[ {M{L^2}{T^{ - 3}}{A^{ - 1}}} \\right] \\\\(b){\\text{ }}\\left[ {M{L^2}{T^{ - 3}}{A^{ - 2}}} \\right] \\\\(c){\\text{ }}\\left[ {ML{T^{ - 3}}{A^{ - 1}}} \\right] \\\\(d){\\text{ }}\\left[ {{M^0}{L^0}{T^0}{A^0}} \\right] \\\\ $

Sky appears blue because of A. reflectionB. ScatteringC. RefractionD. Total internal reflection

Which mode of propagation is used by short wave broadcast services?

The Boolean expression $P + \\bar PQ$ where P and Q are the inputs of the logic circuits represents.$(a)$ AND gate$(b)$ NAND gate$(c)$ NOT gate$(d)$ OR gate

Define resistivity of a material. Give its units.

Elastic waves in solid areA. TransverseB. LongitudinalC. Either transverse or longitudinalD. Neither transverse nor longitudinal

Two capacitors having capacitance \\[{C_1}\\]and \\[{C_2}\\] are charged with 120V and 200V batteries respectively. When they are connected in parallel now it is found that the potential on each of them is zero. Then:$(a){\\text{ 8}}{{\\text{C}}_1} = 5{C_2} \\\\(b){\\text{ 9}}{{\\text{C}}_1} = 5{C_2} \\\\(c){\\text{ 3}}{{\\text{C}}_1} = 5{C_2} \\\\(d){\\text{ 5}}{{\\text{C}}_1} = 3{C_2} \\\\ $

A ray is incident at an angle of incidence i on one surface of a prism of small angle A and emerges normally from the opposite direction. If the refractive surface of the material of the prism is $\\mu $ the angle of the incidence i is nearly equal to:$(a){\\text{ }}\\dfrac{{\\mu A}}{2} \\\\(b){\\text{ }}\\dfrac{A}{{2\\mu }} \\\\(c){\\text{ }}\\mu {\\text{A}} \\\\{\\text{(d) }}\\dfrac{A}{\\mu } \\\\ $

A $50\\Omega $ is connected to a battery of $5V$. A galvanometer of resistance $100\\Omega $ is to be used as an ammeter to measure current through the resistance for this a resistance ${{r}_{s}}$ is connected to the galvanometer. Which of the following connections should be employed if the measured current is within $1\\%$ of the current without the ammeter in the circuit?A. ${{r}_{s}}=1\\Omega $ in parallel with the galvanometerB. ${{r}_{s}}=0.5\\Omega $ in parallel with the galvanometerC. ${{r}_{s}}=0.5\\Omega $ in series with the galvanometerD. ${{r}_{s}}=1\\Omega $ in series with the galvanometer

Which of the following phenomena works on the particle nature of light?A.) InterferenceB.) DiffractionC.) PolarisationD.) Photoelectric effect

Derive the balancing condition of a Wheatstone bridge

Two particles P and Q describe Simple Harmonic Motion (SHM) of same amplitude (a) and frequency (v) along the same straight line. The maximum distance between the two particles is $ \\sqrt { 2 }a $ . The initial phase difference between the particles is:$ A.Zero $ $ B.\\dfrac{\\pi }{2} $ $ C.\\dfrac{\\pi }{6} $ $ D.\\dfrac{\\pi }{3} $

Write definitions for plane of vibration and plane of polarization. Explain the working process to obtain the plane polarized light by Nicol prism. Draw the necessary diagram.

Refractive index of diamonds is 2.42. What do we mean from this?A.) Speed of light in diamond is raised by a factor 2.42 relative to that in vacuumB.) Speed of light in diamond is lower by a factor 2.42 relative to that in vacuumC.) Speed of light in air equals to speed of light in diamondD.) None of the above

The graph between angle of deviation and angle of incidence (i) for a triangular prism is represented by:\n \n \n \n \n \n \n \n \n \n

Two junction diodes one of germanium ( Ge ) and another of silicon (Si ) are connected as shown in the figure to a battery of emf $12V$ and a load resistance $10k\\Omega $. The germanium diode conducts at $0.3V$ and silicon diode at $0.7V$. When a current flows in the circuit then the potential of terminal $Y$will be:\n \n \n \n \n $\\begin{align} A)12V \\\\ B)11V \\\\ C)11.3V \\\\ D)11.7V \\\\ \\end{align}$

Define the following:(A). Define prism angle and angle of deviation of a prism.(B). Write the sequence of colors in the spectrum formed by the passage of white light through prism.(C). Explain the process of formation of a rainbow.

Why does bluish predominate in a clear sky?

The essential difference between AC and DC generator is:a) AC generators have an electromagnet while a DC generator has a permanent magnet.b) DC generators will generate a higher voltage.c) AC generators will generate a higher voltage.d) AC generator has slip rings while the DC generator has a commutator.

A convex lens of focal length 20cm is placed coaxially with a convex mirror of radius of curvature 20cm. The two are kept at 15cm from each other. A point object placed 40cm in front of the convex lens. Find the position of the image formed by this combination.

The magnification produced by an astronomical telescope in normal adjustment is 10 and the length of the telescope is 1.1m. The magnification when the image is formed at the least distance of distinct vision isA. 6B. 18C. 16D. 14

Three charged [particles are initially in position-1. They are free to move and they come to position-2 after some time let ${{U}_{1}}\\text{ and }{{U}_{2}}$be the electrostatic potential energies in position-1 and position-2. ThenA. ${{U}_{1}}={{U}_{2}}$B. ${{U}_{2}}\\ge {{U}_{1}}$C. ${{U}_{2}}{{U}_{1}}$D. ${{U}_{1}}{{U}_{2}}$

Monochromatic light of wavelength 3000 ${A^0}$ is incident on a surface area 4 $c{m^2}$. If intensity of light is 150$mW\/{m^2}$ then rate at which photons strike the target is(A). $3 \\times {10^{10}}\/s$(B). $9 \\times {10^{13}}\/s$(C). $7 \\times {10^{15}}\/s$(D). $6 \\times {10^{19}}\/s$

The period of a satellite in a circular orbit of radius $R$ is $T$. The period of another satellite in a circular orbit of radius $4R$ is:(A). $4T$ (B). $8T$(C). $\\dfrac{T}{4}$(D). $\\dfrac{T}{8}$

A 100 W point source emits monochromatic light of wavelength 6000 $A^o$ Calculate the photon flux (in SI unit) at a distance of 5m from the source. Given $h = 6.6 \\times 10 ^{34}$ Js and $C = 3 \\times 10^8 ms^{-1}$.

In the loop shown the magnetic induction at the point 'O' isA. $\\dfrac{{{\\mu _0}I}}{8}\\left( {\\dfrac{{{R_1} - {R_2}}}{{{R_1}{R_2}}}} \\right)$B. $\\dfrac{{{\\mu _0}I}}{8}\\left( {\\dfrac{{{R_1} + {R_2}}}{{{R_1}{R_2}}}} \\right)$C. $\\dfrac{{{\\mu _0}I}}{8}\\left( {\\dfrac{{{R_1}{R_2}}}{{{R_1} + {R_2}}}} \\right)$D. Zero

State Fleming’s right hand rule. For what purpose is it used?

“A step up transformer increases the AC voltage.” The statement is:(A). True(B). False(C). Ambiguous(D). Data insufficient

An electric pump has 2kw power. How much water will the pump lift every minute to a height of 10m?

What happens to the image distance in the eye when we increase the distance of an object from the eye?

Name the device that uses an electromagnetA. Electric bellB. BarometerC. LactometerD. All the above

Plot a graph between potential difference V and current I through a conductor.

Write two limitations of Bohr’s model.

Dual nature of radiation is shown by:(A). Diffraction and reflection.(B). Refraction and diffraction.(C). Photoelectric effect alone.(D). Photoelectric effect and diffraction.

A Carnot engine takes 900 kcal of heat from a reservoir at $723^\\circ C$ and exhausts it to a sink at $30^\\circ C$. The work done by the engine is:${\\text{A}}{\\text{. 2}}{\\text{.73}} \\times {\\text{1}}{{\\text{0}}^6}{\\text{ Cal}} \\\\{\\text{B}}{\\text{. 3}}{\\text{.73}} \\times {\\text{1}}{{\\text{0}}^6}{\\text{ Cal}} \\\\{\\text{C}}{\\text{. 6}}{\\text{.27}} \\times {\\text{1}}{{\\text{0}}^6}{\\text{ Cal}} \\\\{\\text{D}}{\\text{. 5}}{\\text{.73}} \\times {\\text{1}}{{\\text{0}}^6}{\\text{ Cal}} \\\\ $

To observe refraction and lateral; deviation of a beam of light incident obliquely on a glass slab.

What is the focal length of a double convex lens kept in air with two spherical surfaces of radii ${R_1} = 30cm$ and ${R_2} = 60cm$? (Take the refractive index of lens as 1.5)

Draw a block diagram of a generalized communication system.

The frequency of AC mains in India is:(A). $30\\text{ Hz}$ (B). $50\\text{ Hz}$(C). $60\\text{ Hz}$(D). $120\\text{ Hz}$

What is an amplifier? Draw the simple circuit of the transistor in CE mode.

The time period of simple harmonic motion depends upon the(A). Amplitude(B). Energy(C). Phase constant(D). Mass

A plano-convex lens when silvered at its plane surface is equivalent to a concave mirror of focal length 28 cm. When its curved surface is silvered and the plane surface is not silvered it is equivalent to a concave mirror of focal length 10 cm then the refractive index of the material of the lens is A. $$\\dfrac { 9 }{ 14 } $$B. $$\\dfrac { 14 }{ 9 } $$C. $$\\dfrac { 17 }{ 9 } $$D. None of these

When a ray of light travels from denser to rarer medium:(A). It bends towards the normal (B). It bends away from the normal(C). It goes perpendicularly(D). All

An air bubble in water will act like a:A.) MirrorB.) Convex lensC.) Reflective mirrorD.) Concave lens

Which one has the least penetrating power?A. alpha radiationB. beta radiationC. gamma radiationD. can’t say

What is the resistance of an ideal voltmeter and an ammeter?(A). Infinite and One(B). Fixed and Infinite(C). Zero and Infinite(D). Infinite and Zero

A thermocouple of negligible resistance produces an e.m.f. of \\[40\\mu V\/C\\]in the linearrange of temperature. A galvanometer of resistance \\[10ohm\\]whose sensitivity is\\[1\\mu Adiv\\] is employed with the thermocouple. The smallest value of temperaturedifference that can be detected by the system will be0.5C1C0.1C0.25C

Magnetic dipole moment is a vector quantity directed from:A. South to north poleB. North to south poleC. East to west directionD. West to east direction

In a LCR circuit find the energy stored in the inductor at resonance. If voltage of source is 10V and resistance is \\[10\\Omega \\] and inductance is 1H. A. 0.5JB. 2JC. 4JD. 10J

How is the angle of emergence $'e'$ related to the angle of incidence $'i'$?

The radius of the hydrogen atom when it is in its second excited state becomes _________ its ground state radius.A. halfB. doubleC. four timesD. nine times

The ampere metre and second are SI base units. State two other SI base units.

A proton and an electron have the same kinetic energy. Which one has a smaller de-Broglie wavelength and why?

Distinguish between the phenomenon of interference and diffraction of light.

Draw a neat labelled energy level diagram of the Hydrogen atom.

What is the SI unit of magnetic flux is it a vector or scalar quantity?

State what is meant by the refraction of light. State Snell’s law for the refraction of light and also express it mathematically.The refractive index of air with respect to glass is $\\dfrac{2}{3}$ and the refractive index of water with respect to air is $\\dfrac{4}{3}$. If the speed of the light in glass is $2\\times {{10}^{8}}m\/s$ find the speed of the light in (a) air (b) water.

The angle of deviation when light is incident at an angle of $45{}^\\circ $ on one of the refracting faces of an equilateral prism of refractive index 1.414 is $\\begin{align} \\text{A}\\text{. 40}{}^\\circ \\\\ \\text{B}\\text{. 30}{}^\\circ \\\\ \\text{C}\\text{. 45}{}^\\circ \\\\ \\text{D}\\text{. 50}{}^\\circ \\\\ \\end{align}$

The velocity of light in diamond is $121000km.{{s}^{-1}}$. What is the refractive index?A.)$1.47$ B.)$2.47$ C.)$3.52$ D.)$3.86$

The electric field due to an electric dipole at a distance r from its center in axial position is E. If the dipole is rotated through an angle of ${{90}^{\\circ }}$ about its perpendicular axis the electric field at the same point will be(a). $E$ (b). $\\dfrac{E}{4}$ (c). $\\dfrac{E}{2}$ (d). $2E$

What is the impact parameter in a scattering experiment?

Define angular dispersion.

A coil of inductive reactance 31 has a resistance of 8. It is placed in series with a condenser of capacitive reactance 25. The combination is connected to an alternative current source of 110 V. What is the power factor of the circuit?${\\text{A}}{\\text{.}}$ 0.64${\\text{B}}{\\text{.}}$ 0.75${\\text{C}}{\\text{.}}$ 0.80${\\text{D}}{\\text{.}}$ 0.56

Two identical thin plano-convex glass lenses (refractive index 1.5) each having a radius of curvature of 20 cm are placed with their convex surfaces in contact at the center. The intervening space is filled with the oil of refractive index 1.7. The focal length of the combination is(A). -50 cm(B). 50 cm(C). -20 cm(D). -25 cm

Two concentric coils each of radius equal to 2\\[\\pi \\]cm are placed at right angles to each other. 3 ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic induction in \\[weber\/{m^2}\\] at the center of coils will be ($\\mu = 4\\pi \\times {10^{ - 7}}Wb\/A.m$)A. ${10^{ - 5}}$B. $12 \\times {10^{ - 5}}$C. $5 \\times {10^{ - 5}}$D. $7 \\times {10^{ - 5}}$

State Kirchhoff’s law for an electrical network. Using these laws deduce the condition for balance in a wheatstone bridge.

Derive an expression for electric field intensity due to an electric dipole at a point on its axial line.

What is the e\/m value of an electron?\\[{\\text{A}}{\\text{. }}1.6 \\times {10^{ 11}}\\] C\/kg\\[{\\text{B}}{\\text{. }}1.6 \\times {10^{ - 19}}\\] C\/kg\\[{\\text{C}}{\\text{. }}1.759 \\times {10^{11}}\\] C\/kg\\[{\\text{D}}{\\text{. 901}} \\times {10^{ - 31}}\\] C\/kg

What is the approximate peak value of an alternating current producing four times the heat produced per second by a steady current of 2A in a resistor?(a). 2.8A(b). 4.0A(c). 5.6A(d). 8.0A

Einstein won his Nobel Prize forA. Theory of RelativityB. Explanation of photoelectric effectC. His theory of atomic heats of solidD. None of the above

An electric dipole is held in a uniform electric field.(i) Show that the net force acting on it is zero.(ii) The dipole is aligned parallel to the field. Find the work in rotating it through the angle of ${{180}^{0}}$.

Derive an expression for average power of an AC (alternating current) circuit.

A point is situated at 7cm and 7.2cm from two coherent sources. Find the nature of illumination at the point if the wavelength of light is 4000Å. \t

Consider a parallel plate capacitor of capacity $ 10\\mu F $ with air filled in the gap between the plates. Now one-half of the space between the plates is filled with a dielectric constant $ 4 $ as shown in the figure. The capacity of capacitor changes to:\n \n \n \n \n A. $ 25\\mu F $ B. $ 20\\mu F $ C. $ 40\\mu F $ D. $ 5\\mu F $

The de-Broglie wavelength of an electron moving with a velocity of $1.5\\times {{10}^{8}}m\/s$ is equal to that of a photon. The ratio of kinetic energy of the electron to that of the photon $c=3\\times {{10}^{8}}m\/s$:(a) $2$(b) $4$(c) $\\dfrac{1}{2}$(d) $\\dfrac{1}{4}$

A person suffering from myopia (short-sightedness) can see clearly only up to a distance of 2m. What is the power of a concave lens required to rectify this defect? (A). -0.5D(B). -1.5D(C). -2.0D(D). -2.5D

A silver sphere of radius $1cm$ and work function $4.7eV$ is suspended from an insulating thread in free-space. It is under continuous illumination of $200nm$ wavelength light. As photoelectrons are emitted the sphere gets charged and acquires a potential. The maximum number of photoelectrons emitted from the sphere is $A\\times {{10}^{z}}$(where$1 A 10$). The value of $''z''$ is:

Suppose that the electric field amplitude of an electromagnetic wave propagating along x-direction is ${{E}_{o}}=120N{{C}^{-1}}$ and that its frequency is $\\upsilon =50.0MHz$ A. The expression of electric field is $\\overrightarrow{E}=120\\sin \\left( \\dfrac{\\pi }{3}x-100\\pi \\times {{10}^{6}}t \\right)\\widehat{j}$B. The expression of electric field is $\\overrightarrow{E}=60\\sin \\left( \\dfrac{\\pi }{3}x-100\\pi \\times {{10}^{6}}t \\right)\\widehat{j}$C. The expression of electric field is $\\overrightarrow{B}=40\\times {{10}^{-8}}\\sin \\left( \\dfrac{\\pi }{3}x-\\pi \\times {{10}^{6}}t \\right)\\widehat{k}$D. Both A and C

A and B are two hollow metal spheres of radii 50 cm and 1 m carrying charges 0.6 μC and 1 μC respectively. They are connected externally by a conducting wire. Now the charge flows from:A. A to B till the charges become equalB. A to B till the potentials become equalC. B to A till the charges become equalD. B to A till the potentials become equal

State whether a voltmeter has a high resistance or a low resistance. Give reasons for your answer.

A coil of inductance L is carrying steady current I. What is the nature of its steady energy?A. MagneticB. ElectricalC. Both magnetic and electricalD. Heat

State and explain Coulomb's law in electrostatics.

Why are microwaves used in radar?

For a CE transistor amplifier the audio signal voltage across the collector resistance of $\\text{2k }\\Omega$ is 2V. Suppose the current amplification factor of the transistor is 100. What should be the value of ${{\\text{R}}_{\\text{B}}}$ in series with ${{\\text{V}}_{\\text{BB}}}$ supply of 2V if the dc base current has to be 10 times the signal current. Also calculate the dc drop across the collector resistance. Take ${{\\text{V}}_{\\text{BE}}}$ = 0.6V.

The coefficient of self-inductance and the coefficient of mutual inductance have A.)Same units but different dimensionsB.)Different units but same dimensionsC.)Different units and different dimensionD.)Same unit and same dimension

A T.V transmitting antenna is 128m tall. If the receiving is at ground level the maximum distance between them for satisfactory communication in L.O.S mode is:(Radius of earth=$6.4\\times {{10}^{6}}m$)\\[A.\\quad 64\\times \\sqrt{10}km\\]\\[B.\\quad \\dfrac{128}{\\sqrt{10}}km\\]\\[C.\\quad 128\\times \\sqrt{10}km\\]\\[D.\\quad \\dfrac{64}{\\sqrt{10}}km\\]

Define quality factor.

The bulk modulus of a gas is defined as $B = -V \\dfrac{dP}{dV}$ . For an adiabatic process the variation of B is proportional to $P^n$ for an ideal gas n is : $\\begin{align} \\text{A}\\text{. zero} \\\\ \\text{B}\\text{. 1} \\\\ \\text{C}\\text{. }\\dfrac{\\text{5}}{\\text{3}} \\\\ \\text{D}\\text{. 2} \\\\ \\end{align}$

Write the working of cyclotron in brief. Draw a schematic sketch of the cyclotron showing the path of accelerated charged particles (ions) in the Dees.Derive the following parameters of cyclotron:(a) Cyclotron frequency and(b) Kinetic energy of ions of cyclotron.

Write the names of two universal logic gates. What is an integrated circuit? Write two advantages of it.