Question # 1

Blood has a density

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Equal to water

Greater then water

Lesser then water

None of these

A photocell with a constant p.d of V volt across it illuminated by a point source from a distance of 25 cm. When the source is moved to a distance of 1 m, the electrons emitted by the photocell

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Carry 1/4th their previous energy

Are 1/6th as numerous as before

Are 1/4th as numerous as before

Carry 1/4th their previous momentum

The half life of a radio-isotope is 5 years The fraction of atoms decayed in this substance after 15 years will be

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1

3/4

7/8

5/8

At constant volume temperature is increased then

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Collision on walls will be less

Number of collisions per unit time will increase

Collisions will be in straight lines

Collisions will not change

Copper and germanium are cooled to 70 K from room temperature then

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Resistance of copper increases while that of germanium decreases

Resistance of copper decreases while that of germanium increases

Resistance of both decreases

Resistance of both increases

There are discrete energy levels in atoms. It was first experimentally demonstrated by

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Rutherford's experiment

Frank Hertz experiment

Marsden's experiment

Sommerfield experiment

With the propagation of a longitudinal wave through a material medium the quantities transmitted in the propagation direction are

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Energy momentum and mass

Energy

Energy and mass

Energy and linear momentum

Which of the following lists of physical quantities consists only of vectors:

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Time,temperature,velocity

Force,volume,momentum

Velocity,acceleration,mass

Force,acceleration,velocity

Which of the following sources give discrete emission spectrum?

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Incandescent electric bulb

Sun

Mercury vapour lamp

Candle

In a common base transistor circuit the current gain is 0.98.On changing the emitter current by 5.00 mA, the change in collector current is:

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0.196 mA

2.45 mA

4.9 mA

5.1 mA

In an L-R circuit time constant is that time in which current grows from zero to the value

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0.63 I_o

0.50 I_o

0.73 I_o

I_o

The force between two charges 0.06 m apart is 5 N. If each charge is moved towards the other by 0.01 m, then the force between them will become

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7.20 N

11.25 N

22.50 N

45.00

A sun rise or sun set, the sun looks reddish because:

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The sun is coldest at these times

Of the effects of reflection and refraction

The sun is hottest at these times

Of the scattering of light

The velocity of a particle at an instant is 10 m/s and after 5s the velocity of the particle is 20 m/s. The velocity 3s before in m/s is:

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8

4

6

7

When light wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however, light of 600 nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters?

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1 : 2

2 : 1

4 : 1

1 : 4

In an L-R circuit, time constant is that time in which current grows from zero to the value

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0.63 I_o

0.50 I_o

0.37 I_o

I_o

A converging lens is used to form an image on a screen. When the upper half of the lens is covered by an opaque screen

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Half the image will disappear

No change either in size or in intensity

Intensity of image will increase

Intensity of the image will decrease

A photocell with a constant p.d. of V volt across it illuminated by a point source from a distance of 25 cm. When the source is moved to a distance of 1m, the electrons emitted by the photocell

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Carry 1/4th their previous energy

Are 1/16th as numerous as before

Are 1/4th as numerous as before

Carry 1/4th their previous momentum

When n-type of semiconductor is heated

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Number of electrons increases while that of holes decreases

Number of holes increases while that of electron decreases

Number of electrons and holes remains same

Number of electrons and holes increases equally

A p-n junction has a thickness of the order of:

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1 cm

1 mm

10^-6cm

10^-12cm

At constant volume temperature is increased. Then

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Collision on walls will be less

Number of collisions per unit time will increase

Collisions will be in straight lines

Collisions will not change

The percentage errors in the measurements of mass and speed are 2% and 3% respectively. How much will be the maximum error in the estimate of the kinetic energy obtained by measuring mass and speed

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11%

8%

5%

1%

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