Question # 1

Light of frequency 2 times the threshold frequency is incident on the metalsurface. Ifthe frequency is by quartered and intensity is doubled, the photoelectric becomes

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Quadrupled

Zero

Doubled

Halved

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

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

Maximum speed of electrons in X-rays tube which is producing X-rays photons of frequency f is

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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

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

The potential difference applied to an X-rays tube is increased. As a result, in the emitted radiation

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The intensity increases

The minimum wavelength decrease

The intensity remains unchanged

Both B & C

Interference and diffraction of light confirms its:

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Particle nature

Dual nature

Wave nature

Electromagnetic nature

Most motorbikes have ____________ cylinder/s engine but cars usually have _________ cylinders on the same crankshaft.

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Four , Six

One , four

two , five

None of these

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

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

The centre of gravity of a triangular plate is at

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On end of the plate

The midpoint of any side of the plate

The maximum energy of the electrons released in a photo cell is independent of:

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Frequency of incident light

Intensity of incident light

Nature of cathode rays

None of these

A man pushes a wall and fails to displace it. He does:

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Negative work

Positive but not maximum work

No work at all

Maximum work

A total charge of 100C flows through 12W bulb in a time of 50 second. Which is the potential difference across the bulb during this time?

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0.12V

6.0V

2.0V

24V

If the tension in a string stretched between two fixed points is made four times, the frequency of the fundamental harmonic will become:

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Two times

Three times

Four times

Six times

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

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Infrared

Visible

Ultraviolet

X-rays

A long solenoid has 20 turns/ cm. The current necessary to produce a magnetic field of 20 mellites inside the solenoid is approximately:

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1A

2A

4A

8A

Of electron of 50 keV strike a heavy target. Then radiation emitted by target will be

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Visible light

Radio waves

Ultraviolet

None of these

An engine pumps out 40 kg of water in one second. The water comes out vertically upwards with a velocity of 3ms-1 . What is the power of engine in kilowatt?

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1.2kW

120kW

12kW

1200kW

The nature of thermal radiation is smaller to:

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Ultraviolet rays

Light rays

Both of them

None of these

A steady current is flowing in a conductor of non-uniform cross-section. Thecharge passing through any cross-section per unit time is

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Directly proportional to the area of cross-section

Inversely proportional to the area of cross-section

Proportional to square of the area of cross-section

Independent of the area of cross-section

de-Broglie wavelength associated with an electron moving at a speed of 1x106 ms-1 is

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4x10-10 ms-1

5x10-10 m

6x10-10 m

7x10-10 m

The time period of a geostationary satellite above the surface of the earth is.

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24 hours

12 hours

365 days

none of these

An electric motor exerts a force of 40 N on a cable and pulls it by a distance of 30 m in one minute. The power supplied by the motor in watts is

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20

200

2

10

Two point charges repel each other with a force of 4× 𝟏𝟎−𝟓 newton at a distanceof meter. Two charges are

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Both positive

Alike

Both Negative

Unlike

The energy stored in wound watch spring is

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K.E.

P.E.

heat energy

chemical energy

A force of 6 N act horizontally on a stationary mass of 2kg for 4s. The kineticenergy in joule is

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12

72

56

888

Choose incorrect about properties of photon

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Rest mass of photon is zero

A photon is never at rest

Photon is not deflected by electric field not by magnetic field

The velocity of photon is different in different media

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

A soap bubble is give a negative charge, then its radius:

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Decrease

Remains same

Increases

Bubble will disappear

A.H Compton studied the scattering of X-rays by loosely bound electrons from a graph target in:

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1905

1911

19251

1923

One degree of thermodynamics scale of temperature is called:

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Celsius

Fahrenheit

Kelvin

Radian

A light and a heavy body have equal momenta. Which one has greater K.E?

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The light body

The heavy body

The K.E are equa

Data is incomplete

A positively charged particle is moving perpendicular to a uniform magnetic field. The magnetic force makes the particle to move along:

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An elliptical path

A circular path

A parabolic path

None of these

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

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

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Heat

Temperature

Chemicial

None of these

A car of 1000kg traveling at 20m/sec rounds a curve of radius 100m. Find the necessary centripetal force

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4 x 10³ kg m/s²

3 x 10³ kg m/s²

5 x 10³kg m/s²

4.5 x 10³kg m/s²

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

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

Which of the particles, electron, proton and neutron moving with same speed has longest wave length?

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Electron

Proton

Neutron

All have same