Question # 1

In closed end organ pipe, the frequency of first harmonic is 300 Hz. The frequency ofthird overtone is :

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900 Hz

1500 Hz

2100 Hz

600 Hz

If a molecule with momentum mv strikes a wall and rebound then the change in momentum will be:

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-2 mv

Zero

2 mv

mv

A piece of Aluminium (Al) and a piece of Germanium (Ge) are cooled T1 K to T2 K. The resistance of:

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Each of them increases

Each of them decreases

Al increases and Ge decreases

Al decreases and that of Ge increases

Monochromatic light of wavelength 300 nm is incident normally on a surface of area 4 cm2.

If the intensity of light is 150 mW/m2; the rate at which photon strike the surface:

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2.53 × 1019

7.5 × 1019

9.1 × 1013

2.53 × 1013

A 50 kg man with 20 kg load on his head climbs up 20 steps of 0.25 m height each. The work done in climbing is

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5 J

350 J

100 J

3430 J

One degree of thermodynamics scale of temperature is called:

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Celsius

Fahrenheit

Kelvin

Radian

Car X is traveling at half the speed of car Y. Car X has twice mass of car Y.

Which statement is correct?

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Car X has half the kinetic energy of car Y

Car X has one quarter of the kinetic energy of car Y

Car X has twice the kinetic energy of car Y

The tow cars have the same kinetic energy

Tick which of the following is not state variable:

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Heat energy

Pressure

Entropy

Volume

With the propagation of longitudinal waves through a material medium, the quantitiestransferred in the direction of propagation are:

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Energy, momentum and mass

Energy and momentum

Energy and mass

Energy

In a full wave rectifier:

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DC current is twice that of half wave rectifier

DC pulses are twice per cycle that of half wave rectifier

DC voltage is twice that of half wave rectifier

All are correct

Which of the following is a unit of energy?

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unit

whatt

Horse Power

None of the above

Which one is the correct express of de-Broglie equation for the length of atoms of mass m at temp? T(k=Boltzmann’s constant):

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The product of resistance and conductance of a resistors is equal to:

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1

Conductivity

Resistivity

Zero

A parallel plate air capacitor is charged and then isolated. When a dielectric material is inserted between the plates of the capacitor , then which of the following does not change:

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Electric field between the plates

Charge on the plates

Potential difference across the plate

Energy stored in the capacitor

Hotness and coldness of an object is represented in terms of:

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Heat

Temperature

Chemicial

None of these

During a negative β-decayv

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An atomic electron is ejected

A neutron in the nucleus decays emitting an electron

An electron which already present within the nucleus is ejected

A part of binding energy of nuclei is converted into electron

How many photons per second does a one-watt bulb emit if its efficiency is 10% and the wavelength of light is 500 nm:

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2.53 × 1017

2.53 × 1019

7.5 × 1019

7.5 × 1017

When a radioactive nucleus remits a beta particle, the proton neutron ratio:

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Decreases

Increases

Remain same

None of the above

The stopping potential for a certain metal is 10 volt, the max. Energy of emitted electron is:

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10 J

100 J

1.6 × 10-18 J

1.6 × 10-19 J

On slightly disturbing a body which is an unstable equilibrium, its center of gravity

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rises

falls

remains constant

first rises then falls

A point on the rim of wheel 400 cm in diameter has a velocity of 1600 cms-1 . The angular velocity of the wheel is:

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6 rad/s

4 rad/s

2 rad/s

8 rad/s

A charge of 2C experiences a force 2000N in a uniform electric field. In this fieldthe potential difference between two points separated by a distance 1cm is

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2V

10V

5V

20V

A photo cell is based on:

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Compton effect

Pair production

Photo cell

All of these

A person weighing 20 mg walks on a level platform with a speed of 2 ms-1 . The work by the person against the force of gravity is:

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Zero

2J

60J

600J

The spectrum of a star’s light is measured and the wavelength of one of the lines as thesodium’s line is found to be 589 nm. The same line has the wavelength of 497 nm whenobserved in the laboratory. This means the star is

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Moving away from the earth

Moving towards the earth

Stationary

Revolving around the planet

An electron in the n=1 orbit hydrogen atom is bound by 13.6 eV. If a hydrogen atom is in the n=3 state, how much energy is required to ionize it:

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13.6 eV

4.53 eV

3.4 eV

1.51eV

An electric room radiator, which operates at 50V has resistance of 50 Ω. Power of the radiator is approximately:

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100W

50W

450W

1000W

A point on the rim of a wheel 4m in diameter has a velocity of 1600 cm s-1. The angular velocity of the wheel is

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2 rad s^-1

4 rad s^-1

6 rad s^-1

8 rad s^-1

The maximum energy of the photoelectrons depends upon:

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Frequency of incident light

Intensity of incident light

Nature of metal

Both (a) & (c)

Ultraviolet radiation of 6.2 eV falls on an aluminium surface having work function ∅ = 𝟒. 𝟐 𝒆𝑽.

The kinetic energy of the fastest electron emitted is:

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4 eV

2 eV

2.2 eV

1.2 eV

When a particle moves in a circle the angle between it linear velocity and the angular velocity is always

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0°

180°

90°

none of them

A body revolved around the sun 27 times faster then the earth what is the ratioof their radii

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1/27

1/4

1/9

1/3

The number of molecules in one mole of gas is equal to:

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Avogadro number N_A

Gas constant R

Boltzmann constant k

None of these

A ball takes ‘t’ second to fall from a height 𝒉𝟏 and ‘2t’ second to fall from a height 𝒉𝟐 then h1/h2 is:

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2

4

0.5

0.25

In thermodynamics, the change in internal energy depends upon:

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The path taken between initial and final states

The initial state only

The final state only

Initial and final states

For X-rays which of the following is not correct:

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Cause of ionization in air when they pass through it

Can be deflected by electric and magnetic fields

Can be used to detect flaws in metal casting

Travel with the speed of light

Electric current is defined as:

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Flow of charges through conductor

Rate of flow of charges through conductor

Flow of electrons

Flow of protons

In which region of the electromagnetic spectrum does the Lyman series of hydrogen atom lie?

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Infrared

Visible

Ultraviolet

X-rays

Temperature of black body radiating at 270c is increased to 327oc, then emittedenergywill increase by

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2 times

12 times

16 times

4 times

A satellite moving round the earth constitute

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An inertial frame of reference

Non inertial frame

Neither inertial nor non inertial

Both inertial and non-inertial

A body gets positive charge. It means that:

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It has lost electrons

It has gained positions

It has gained protons

It has gained 𝛼 −particles