Question # 1

The reverse process of photo-electric effect is called:

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Pair production

Compton effect

Annihilation of matter

X-rays

When heat is added to the system, the entropy change is:

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Positive

Negative

Zero

None of these

If the radioactive substance reduces to 𝟏 𝟏𝟔 PHYSICS of its original mass in 40 days then its half-life is:

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10days

20days

40days

4days

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

Light of frequency 4f0 is incident on the metal of the threshold frequency f0. The maximum kinetic energy of the emitted photoelectrons is

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3h f0

3/2h f0

2h f0

1/2h f0

As in linear motion force determines linear acceleration where as in circular motion torque determines its

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Angular acceleration

Linear acceleration

Vibratory acceleration

Tangential acceleration

Only those processes are probable to take place for which entropy os the system:

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Increases

Remains constant

Both A and B are correct

None of above

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

In which process the change in internal energy of the system is zero:

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Isochoric process

Isobaric process

Adiabatic process

Isothermal process

Light of frequency 1.5 times the threshold frequency is incident on a photo sensitive material. If the frequency is halved and intensity is doubled the photo electric current becomes

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Four times

Half

Double

Zero

An electric field can deflect:

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X-rays

Neutrons

𝛼 −particles

𝛾 −rays

For a normal AC cycle, during T/2 to T the diode act as:

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Open switch

full wave rectifier

Close switch

All are correct

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 whistle is revolved with high speed in a horizontal circle of radius R. to an observer at the centre of the circle the frequency of the whistle will appear to be:

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Decreasing

Increasing

Both

Constant

When a radioactive nucleus emits a 𝖰 −paritcles, the mass number of the atom:

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Increases by one

Decreases by one

Remains the same

Decreases by four

Two satellites are going around the earth at a height of 250 km and 450 km respectively. If angular speed for both is same, then centripetal acceleration will be.

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more for first

more for second

same for both

nothing can be decided

The coulomb’s law is valid for the charges which are:

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Moving and point charges

Stationary and point charges

Moving and non-point charges

Stationary and large size charges

Two artificial satellites of unequal masses are revolving in a circular orbit around the earth with a constant speed. Their time periods:

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Will be different

Will depend on their masses

Will be same

Will depend upon the place of their projection

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

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 threshold frequency depends on the nature on:

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Natural frequency

Photosensitive anode

Photosensitive cathode

Photon

The temperature at which all the gases become liquid is called:

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273 K

-273 K

Absolute Zero

Both (B) and (C)

In order to increase the K.E of ejected photo electrons, there should be an increase in:

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Intensity of radiation

NoneI

Frequency of radiation

Both (b) & (c)

A radioactive nucleus can emit:

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Electron

𝛼 particles

Positron

Any of these

In photo electric cell, the photo electric current

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Decreases with increase in frequency of light

Depends on intensity and frequency of light

Does not depend upon the frequency of light and but depends upon intensity of light

Increases with increase in frequency of light

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

Which of the following have maximum ionization power?

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𝛼 −rays

𝛽 −rays

𝛾 −rays

Same for all

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

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

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

A human eye can detect the electromagnetic radiations of the type:

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Infrared radiations

For- infrared radiations

X-rays radiations

Red radiations

In a photocell, cesium coated oxidized silver emits electrons for :

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Visible light

Infrared light

Ultraviolet light

All of these

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

Bats navigate and find food by:

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Ultrasonic

Echolocation

Refraction

The temperature scale approved in SI units is:

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Calslus scale

Kelvin scale

Fehrenhelt scale

None of these

A proton and an 𝑎 − 𝒑𝒂𝒓𝒕𝒊𝒄𝒍𝒆 are accelerated through same voltage, the ratio of their de- Broglie wavelength will be:

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1:2

√2: 1

2√2: 1

2:1

Electromagnetic waves emitted by hot bodies are called:

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Photoelectrons

Alpha rats

Thermal radiation

None of these

Threshold wavelength for metal having work function 𝝋 is 𝝀. What is the threshold wavelength for metal having work function 2 𝒊𝒔:

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/𝟐

2

4

𝝀/𝟒

For a particle in uniform circular motion the relation a = r 𝑎 of accelerations hold. The acceleration 'a'

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is centripetal acceleration

Is tangential acceleration

is radical acceleration

both A and B

No of spark plugs needed in diesel engine is:

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Four

Five

Six

None of these

Capacitance of a capacitor does not depend upon

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Separation between plates

Thickness of the plates

Area of the plates

Medium between the plates