Question # 1

The frequency and work function of an incident photon are n and𝝋𝟎. If f0 is the threshold frequency, then necessary condition for the emission of photo electron is:

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< 𝑓0

𝑓 ≥ 𝑓0

f = 𝑓0/2

None of these

If the stone is thrown up vertically and return to ground, its potential energy is maximum

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during the upward journey

at the maximum height

at the bottom

A machine gun fires ‘n’ bullets per second and the mass of each bullet is m. If v is the speed of each bullet then the force exerted on the machine gun is:

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mng

mnv

mnvg

mnv/g

In uniform circular motion, the factor that remains constant is

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Linear velocity

Centripetal force

Acceleration

speed

Where in standing wave, do the vibrations of the medium occur?

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Only at the nodes

Only at the antinodes

At all points between the nodes

At all points between the antinodes

Charge on a capacitor is 50C. if voltage applied across its plates is 10V then its capacitance:

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5F

0.02F

500F

0.2F

In 420 days, the activity of a sample of polonium (Po) fell to one-eight of its initial value. The half-life of polonium is :

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140days

45days

87days

90days

The equation PVr = Constant applies to:

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Isothermal process

Adiabatic process

Isobaric process

None of these

The temperature scale approved in SI units is:

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Calslus scale

Kelvin scale

Fehrenhelt scale

None of these

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 charged conductor has charged on its:

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Outer surface

Surrounding surface

Inner surface

Middle point

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

If the K.E. of a body is increased by 300%, its momentum will increase by:

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100 %

150 %

√300%

175 %

When two semiconductors of p- and n-type are brought into contact, they from a p-n junction which act like a:

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Conductor

Amplifier

Oscillator

Rectifier

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

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 man M₁ of mass 80 kg runs up a staircase in 15s. Another man M₂ also of mass 80 kg runs up the same staircase in 20s. The ratio of the power developed by them will be

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1

4/3

16/9

none of these

In a full wave rectifier, the diode conducts during

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Both halves of the input cycle

A portion of the positive half cycle of the input

Positive half cycle of the input

Both halves of the input cycle

Nuclear fission experiments show that the neutrons the uranium nuclei into two fragment of about the same size. This process is accompanied by the emission of several:

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Protons and positrons

𝛼 −partilces

neutrons

Protons and 𝛼 −partilces

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

The time taken by an engine of power 10 kW to lift a mass of 200 kg to a heightof 40 m is (g + 10ms2)

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2 sec

4 sec

8 sec

16sec

In case of planets the necessary acceleration is provided by

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Gravitational force

coulomb force

frictional force

centripetal force

Which of the following is not true?

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The Lyman series is a continuous spectrum

The Ballmer series is a line spectrum in the visible region

The Paschen series is a line spectrum in the infrared region

The spectral series formula can be derived from Rutherford’s model of the hydrogen atom 18. The photoelectric effect is the ejection of

During a negative β-decay

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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

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

The maximum kinetic energy of emitted photoelectrons depends upon:

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The intensity of incident light

Frequency of the incident light

Temperature of the surface

All of above

Light elements do not emit X-rays because

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Electrons in it have high binding energy

These materials are non- material

There is a small difference in their energy shells

Electrons in it require very large energy to remove from these materials

J.J Thomson finds:

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Particle nature of the electron

Dual nature of electron

Wave nature of electron

Electromagnetic nature of electron

A straight current carrying conductor experiences maximum forces in a uniform magnetic field when it is placed:

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Parallel to the field

Perpendicular o the field

At an angle of 45 to the field

None of these

What is the momentum of a photon of light of wavelength 500 nm in kgm/s:

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1.32 × 10−21

1.32 × 10−23

1.32 × 10−25

1.32 × 10−27

The most penetrating radiations out of the following is that of

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𝛾-rays

β-rays

α-particles

X-rays

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

In a half wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be:

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25 Hz

70.7 Hz

50 Hz

100 Hz

The angle of projection, at which the range of projectile would become half of its maximum value.

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45Degree

30Degree

15Degree

60 Degree

To find longest wavelength radiation in Ballmer series, the value of n used is:

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2

3

4

∞

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

The de-Broglie wavelength of the particle of mass m and energy E is:

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ℎ

𝜆 = ℎ√2𝑚𝐸

𝜆 = 1

The ‘emf ’ is always even when no current is drawn through the battery of the cell:

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Zero

Present

Absent

Maximum

A man weighing 500 N carries a load of 10 kg to the top of a building in 4 minutes. The work done by the man is 6 × 𝟏𝟎⁴ J. If he carries the same load in 8 minutes, the work done by the man will be:

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3 × 10⁴ J

6 × 10⁴J

9 × 10⁴J

12× 10⁴ J

Diesel engine coverts ____________ of available heat energy into work.

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20% to 25%

25% to 30%

30% to 35%

35% to 40%