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# Question Paper Solutions - Physics 2017 - 2018-H.S.C-12th Board Exam Maharashtra State Board (MSBSHSE)

Marks: 70
[7]1 | Select and write the most appropriate answer from the given alternative for each sub-question
[1]1.1

In the stationary wave, the distance between a node and its adjacent antinode is _______.

(a) λ

(b) lambda/4

(c) lambda/2

(d)  2λ

Chapter: [8] Stationary Waves
Concept: Formation of Stationary Waves on String
[1]1.2

If the source is moving away from the observer, then the apparent frequency _____.

(a) will increase

(b) will remain the same

(c) will be zero

(d) will decrease

Chapter: [7] Wave Motion
Concept: Wave Motion Introduction
[1]1.3

A particle of mass m performs the vertical motion in a circle of radius r. Its projectile energy at the highest point is _______. (g is acceleration due to gravity)

(a) 2 mgr

(b) mgr

(c) 0

(d) 3 mgr

Chapter: [1] Circular Motion
Concept: Vertical Circular Motion Due to Earth’s Gravitation
[1]1.4

The compressibility of a substance is the reciprocal of _________.

(a) Young’s modulus

(b) bulk modulus

(c) modulus of rigidity

(d) Poisson's ratio

Chapter: [5] Elasticity
Concept: Eneral Explanation of Elastic Property
[1]1.5

If the particle starts its motion from mean position, the phase difference between displacement and acceleration is ______.

(b) pi/2 rad

(c) pi  rad

(d) pi/4 rad

Chapter: [10.01] Oscillations
Concept: Some Systems Executing Simple Harmonic Motion
[1]1.6

The kinetic energy per molecule of a gs at temperature T is ________.

(a) (3/2)RT

(b) (3/2)K_BT

(c) (2/3) RT

(d) (3/2)("RT"/M)

Chapter: [7] Thermal Properties of Matter
Concept: Temperature and Heat
[1]1.7

A thin ring has mass 0.25 kg and radius 0.5 m. Its moment of inertia about an axis passing through its centre and perpendicular to its plane is _______.

(a) 0. 0625 kg m2

(b) 0.625 kg m2

(c) 6. 25 kg m2

(d) 62. 5 kg m2

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[12]2 | Attempt Any Six
[2]2.1

State Kepler's law of orbit and law of equal areas.

Chapter: [2] Gravitation
Concept: Kepler’S Laws
[2]2.2

State any four assumptions of kinetic theory of gases.

Chapter: [9] Kinetic Theory of Gases and Radiation
Concept: Kinetic Theory of Gases- Assumptions
[2]2.3

Define moment of inertia. State its SI unit and dimensions.

Chapter: [3] Angular Momentum
Concept: Physical Significance of M.I (Moment of Inertia)
[2]2.4

Distinguish between centripetal and centrifugal force.

Chapter: [1] Circular Motion
Concept: Centrifugal Forces
[2]2.5

In Melde’s experiment, when the tension in the string is 10 g wt then three loops are obtained. Determine the tension in the string required to obtain four loops, if all other conditions are constant.

Chapter: [8] Stationary Waves
Concept: Formation of Stationary Waves on String
[2]2.6

Calculate the work done in increasing the radius of a soap bubble in air from 1 cm to 2 cm. The surface tension of soap solution is 30 dyne/cm. (Π = 3.142).

Chapter: [7.02] Mechanical Properties of Fluids
Concept: Surface Tension
[2]2.7

A falt curve on a highways has a radius of curvature 400 m. A car goes around a curve at a speed of 32 m/s. What is the minimum value of the coefficient of friction that will prevent the car from sliding? (g = 9.8 m/ s2)

Chapter: [1] Circular Motion
Concept: Banking of Roads
[2]2.8

A particle performing linear S.H.M. has the maximum velocity of 25 cm/s and maximum acceleration of 100 cm/ m2. Find the amplitude and period of oscillation. (π = 3.142)

Chapter: [4] Oscillations
Concept: Differential Equation of Linear S.H.M.
[9]3 | Attempt Any Three
[3]3.1

Derive Laplace’s law for spherical membrane of bubble due to surface tension.

Chapter: [7.02] Mechanical Properties of Fluids
Concept: Surface Tension
[3]3.2

State and prove : Law of conservation of angular momentum.

Chapter: [4] Force
Concept: Torque and Angular Momentum
[3]3.3

Calculate the strain energy per unit volume is a brass wire of length 3 m and area of cross - section 0.6 mm2 when it is stretched by 3 mm and a force of 6 kgwt is applied to its free end.

Chapter: [5] Elasticity
Concept: Definition of Stress and Strain
[3]3.4

What is the decrease in weight of a body of mass 500 kg when it is taken into a mine of depth 1000 km? (Radius of earth R = 6400 km, g = 9.8 m/s2)

Chapter: [6] Gravitation
Concept: Acceleration Due to Gravity and Its Variation with Altitude and Depth
[7]4 | Attempt Any One
[7]4.1

State the differential equation of linear simple harmonic motion.

Chapter: [10.01] Oscillations
Concept: Simple Harmonic Motion

Hence obtain the expression for acceleration, velocity and displacement of a particle performing linear S.H.M.

Chapter: [10.01] Oscillations
Concept: Simple Harmonic Motion

A body cools from 80° C to 70° C in 5 minutes and to 62° C in the next 5 minutes. Calculate the temperature of the surroundings.

Chapter: [7] Thermal Properties of Matter
Concept: Temperature and Heat
[7]4.2

What is meant by harmonics?

Chapter: [8] Stationary Waves
Concept: Study of Vibrations of Air Columns

Show that only odd harmonics are present as overtones in the case of an air column vibrating in a pipe closed at one end.

Chapter: [8] Stationary Waves
Concept: Study of Vibrations of Air Columns

The wavelengths of two sound waves in air are 81/173m and 81/170m. They produce 10 beats per second. Calculate the velocity of sound in air

Chapter: [10] Oscillations and Waves
Concept: Beats
[7]5 | Select and write the most appropriate answer from the given alternatives for each sub-question :
[1]5.1

The reflected waves from an ionosphere are _____.

(a) ground waves

(b) sky waves

(c) space waves

(d) very high-frequency waves

Chapter: [10.01] Communication Systems
Concept: Propagation of Electromagnetic Waves
[1]5.2

In interference pattern, using two coherent sources of light; the fringe width is ________

(a) directly proportional to the wavelength

(b) inversely proportional to the square of the wavelength

(c) inversely proportional to wavelength.

(d) directly proportional to the square of the wavelength.

Chapter: [11] Interference and Diffraction
Concept: Interference of Light
[1]5.3

Electric intensity outside a charged cylinder having the charge per unit length 'λ' at a distance from its axis is ________.

(a) E = (2pi in_0 lambda)/(Kr^2)

(b) E = (in_0 lambda)/(2piKr^2)

(c) E = lambda/(2piin_0Kr)

(d) E = (4piin_0lambda)/(Kr^2)

Chapter: [12] Electrostatics
Concept: Applications of Gauss’s Law
[1]5.4

SI unit of potential gradient is _______.

(a) V cm

(b) V/"cm"

(c) Vm

(d) V/m

Chapter: [13] Current Electricity
Concept: Potentiometer
[1]5.5

The momentum associated with the photon is given by_______.

(a) hv

(b) "hv"/c

(c) hE

(d) hλ

Chapter: [17] Electrons and Photons
Concept: Particle Nature of Light
[1]5.6

A pure semiconductor is ________.

(a) an extrinsic semiconductor

(b) an intrinsic semiconductor

(c) p-type semiconductor

(d) n-type semiconductor

Chapter: [19] Semiconductors
Concept: Electrical Properties - Applications of N-type and P-type Semiconductors
[1]5.7

The glass plate of refractive index 1.732 is to be used as a polarizer, its polarising angle is _______.

(a) 30°

(b) 45°

(c) 60°

(d) 90°

Chapter: [6.02] Wave Optics
Concept: Polarisation
[12]6 | Attempt Any Six
[2]6.1

State the conditions to get constructive and destructive interference of light.

Chapter: [11] Interference and Diffraction
Concept: Interference of Light
[2]6.2

State Ampere’s circuital law

Chapter: [14] Magnetic Effects of Electric Current
Concept: Ampere’s Circuital Law

Explain Ampere’s circuital law.

Chapter: [14] Magnetic Effects of Electric Current
Concept: Ampere’s Circuital Law
[2]6.3

Draw the block diagram of a receiver in communication system

Chapter: [10.01] Communication Systems
Concept: Elements of a Communication System
[2]6.4

Define magnetization. State its formula and S.I. unit.

Chapter: [15] Magnetism
Concept: Magnetisation and Magnetic Intensity
[2]6.5

The electron in the hydrogen atom is moving with a speed of 2.3x106 m/s in an orbit of radius 0.53 Å. Calculate the period of revolution of the electron. (Π = 3.142)

Chapter: [15] Magnetism
Concept: Magnetic Dipole Moment of a Revolving Electron
[2]6.6

A capacitor of capacitance 0.5 μF is connected to a source of alternating e.m.f. of frequency 100 Hz. What is the capacitive reactance? (Π = 3.142)

Chapter: [4.02] Alternating Current
Concept: Reactance and Impedance
[2]6.7

Calculate the de-Broglie wavelength of an electron moving with one-fifth of the speed of light.Neglect relativistic effects. (h = 6.63 xx 10^(-34) J.s, c= 3xx10^8m/s, mass of electron = 9 xx 10^(-31) kg)

Chapter: [7] Dual Nature of Radiation and Matter
Concept: de-Broglie Relation
[2]6.8

In a cyclotron, the magnetic field of 1.4 Wb/m2 is used. To accelerate protons, how rapidly should the electric field between the Dees be reversed? (Π = 3.142,Mp = 1.67 x 10-27 kg, e  = 1.6 x 10-19 C)

Chapter: [3.01] Moving Charges and Magnetism
Concept: Motion in Combined Electric and Magnetic Fields - Cyclotron
[9]7 | Attempt Any Three
[3]7.1

Explain with a neat circuit diagram how will you determine unknown resistance ‘X' by using meter bridge

Chapter: [2.01] Current Electricity
Concept: Wheatstone Bridge
[3]7.2

What is Zener diode?

Chapter: [19] Semiconductors
Concept: Zener Diode as a Voltage Regulator

Describe, with the help of a circuit diagram, the working of Zener diode as a voltage regulator.

Chapter: [19] Semiconductors
Concept: Zener Diode as a Voltage Regulator
[3]7.3

In a biprism experiment, the light of wavelength 5200Å is used to get an interference pattern on the screen. The fringe width changes by 1.3 mm when the screen is moved towards biprism by 50 cm. Find the distance between two virtual images of the slit.

Chapter: [11] Interference and Diffraction
Concept: Interference of Light
[3]7.4

The refractive indices of water and diamond are 4/3 and 2.42 respectively. Find the speed of light in water and diamond. (c = 3x108 m/s)

Chapter: [6.02] Wave Optics
Concept: Huygens Principle
[7]8 | Attempt Any One
[7]8.1

Prove theoretically the relation between e.m.f. induced in a coil and rate of change of magnetic flux in electromagnetic induction. A parallel plate air condenser has a capacity of 20µF. What will be a new capacity if:

1) the distance between the two plates is doubled?

2) a marble slab of dielectric constant 8 is introduced between the two plates?

Chapter: [4.02] Alternating Current
Concept: Power in Ac Circuit: the Power Factor
[7]8.2

Draw a neat and labelled energy level diagram and explain Balmer series and Brackett series of spectral lines for the hydrogen atom.

Chapter: [8.01] Atoms
Concept: Hydrogen Spectrum

The work function for a metal surface is 2.2eV. If the light of wavelength 5000Å is incident on the surface of the metal, find the threshold frequency and incident frequency. Will there be an emission of photoelectrons or not? (c = 3 x 108 m/ s, 1eV = 1.6x10-19 J , h = 6.63 x 10-34 J.s.)

Chapter: [17] Electrons and Photons
Concept: Einstein’s Equation - Particle Nature of Light
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