Question # 1

The number of electrons emitted depend upon

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Colour of target surface

Shape of surface

Frequency of incident light

Intensity of incident light

When resistances are connected in Parallel, the effective resistance will be

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Product of the reciprocals of the individual resistances

Product of the individual resistances

Sum of the reciprocals of the individual resistances

Sum of the individual resistances

A bomb of mass 30 kg at rest explodes into two pieces of masses 18 kg and 12 kg. The velocity of 18 kg mass is 6 ms¹ The KE of other mass is

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324 J

256 J

245 J

524 J

Two bodies are projected at angle 𝜽 𝒂𝒏𝒅 (𝟗𝟎 − 𝜽) to the horizontal with the same speed. The ratio of their times of flight is:

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sin 𝜃 : 1

cos 𝜃 : 1

sin 𝜃 : cos𝜃

cos 𝜃 : sin𝜃

A closed organ pipe and an open organ pipe have their first overtones of identicalfrequency. Their respective lengths are in the ratio:

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1 : 2

4 : 3

2 : 3

3 : 5

Speedometer of an automobile measures

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Average velocity

Instantaneous velocity

Acceleration

Instantaneous speed

The activity of a radioactive sample is 1.6 curie and half-life is 2.5 days. Its activity after 10 days will be:

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0.8 Curie

0.1Curie

0.4 Curie

0.16 Curie

The same retarding force is applied to stop a train. The train stops after 80 m. If the speed is doubled, then the Stopping distance will be:

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The same

Doubled

Halved

Four times

A body moving in a circular path with a constant speed has a

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Constant velocity

Constant kinetic energy

Constant acceleration

Constant displacement

The relationship between Boltzmann constant K with R and N_Ais given as:

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k = RN_A

k = R/N_A

k = NR/N_A

None of these

In a closed organ pipe, the fundamental frequency is f. What will be the ratio of thefrequencies of the next three overtones?

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2 : 3 : 4

3 : 7 : 11

3 : 4 : 5

3 : 5 : 7

The uranium Nucleus 𝟐𝟑𝟖 𝑼 undergoes successive decays, emitting respectively 𝑎 − 𝒓𝒂𝒚,𝖰 − 𝒓𝒂𝒚 𝒂𝒏𝒅 − 𝒓𝒂𝒚𝒔. What is the atomic number and atomic mass of the resulting nucleus:

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90, 238

91, 234

92, 236

92, 238

electrons from the surface of a metal when:

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It is heated to a high temperature

Radiation of suitable wavelength falls on it

Electrons of suitable velocity strike it

It is placed in a strong electric field

In an ideal gas, the molecules have:

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Kinetic energy only

Potential energy only

Both KE and PE

None of these

Truth of kinetic energy theory is confirmed by:

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Diffusion of gases

Brownian motion

Both A and B

None of these

The angular analogue of linear displacement is called

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angular velocity

angular displacement

angular momentum

moment of force

A particle is moving with constant speed by keeping itself at constant distance from a fixed point in a given plane. Its motion is

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Circular motion

Uniform circular motion

Uniform circular motion with fixed axis of rotation

Uniform circular motion with axis of rotation not defined

The only significant motion possessed by the mono-atomic gas molecules is:

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Translatory

Rotatory

Vibratory

None of these

If the momentum of a body is increased n times, its kinetic energy increases:

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n times

2 n times

√𝑛 times

n 2 time

Inverting amplifier circuits have

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A very high input impendance

A very low input impendance

A low output impendance

Both A and C

Photo cells are used for :

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Security and counting system

Automatic door system

Automatic street lighting

All of these

A string vibrates in 1 loop has frequency 25 Hz if it moves in 2 loops its frequencywould be:

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25 Hz

50 Hz

12.5 Hz

5Hz

A radioactive isotope 𝟐𝟑𝟖 𝑼 decays consecutively to 𝟐𝟑𝟒 𝑼 the particles emitted are:

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One 𝛼 and one 𝛽

Two 𝛼 and one 𝛽

e 𝛼 and two 𝛽

Two 𝛼 and two 𝛽

The magnetic field due to the electric current in a conducting wire is:

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Towards the centre of the conducting wire

Circular around the conducting wire

In the direction of the electric current

In the direction opposite to the electric current

The phenomenon of radioactivity is associated with:

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Fission of nucleus

Disintegration of neutrons

Emission of spectral lines

Spontaneous disintegration of the nuclei of atoms

If a source of emf is traversed from positive to negative the potential change will be:

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Positive

Negative

Zero

Constant

The relative permittivity of air is

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1

3.7

7.8

1.0006

A particle executing one dimensional motion, finally comes to rest, what will be the angle between acceleration and displacement during motion:

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0

π

𝜋/2

𝜋/4

A church organ consist of open ended pipes ranging from 4m to 4 mm, if the speed ofsound is considered as 400 m/s then the min and max frequency is:

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400 Hz and 4 kHz

100 Hz and 100 kHz

50 Hz and 50kHz

400 Hz and 400 kHz

A listener observes the frequency “f” of stationary source. If it move toward with 3 times of velocity of sound. Then the apparent frequency of the sound will be

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f

3f

f/2

4f

According to Bohr’s theory, a line in the Ballmer series arises when the electron jumps from any of the higher orbits to the orbit with quantum number:

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1

2

3

4

Charge to mass ratio (e/m) of a charge particle is also called its:

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Specific charge

Specific Force

Gyro-magnetic ratio

Magneto-mechanical ratio

If velocity time graph is a straight line parallel to time axis then body is

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Moving with zero acceleration

Moving with constant velocity

Covering equal displacement in equal intervals of time

All of these

A PN junction diode cannot be use:

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As rectifier

For converting light energy to electrical energy

For getting light radiation

For increasing the amplitude of an ac signal

A proton, accelerated through a p.d V has a certain de Broglie wavelength. In order to have the same de Broglie wavelength, an 𝑎 −particles must be accelerated through a potential difference:

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4V

8V

V/4

V/8

The most penetrating radiations out of the following is that of

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𝛾-rays

β-rays

α-particles

X-rays

If a rotating body is moving counter clockwise, direction of angular velocity will be

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along linear velocity

towards the center

along the axis of rotation

away from center

A count rate 240 per minute reduces to 30 counts per min in 1 hour. The half-life of source is:

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20min

60min

80min

90min

Avogadro number is known as number of molecules in:

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One kg of a substance

Unit volume of a substance

One mole of a substance

None of these

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 force which can do no work on the body on which it acts:

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Frictional force

Elastic force

Gravitational force

Centripetal force