Question # 1

The length contraction happens only

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Opposite to the direction of motion

along the direction of motion

perpendicular to the direction of motion

In any direction

Photoelectrons are emitted when ultraviolet light falls on:

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Casium

Silver

Potassium

Any of these

None of these

The Nobel Prize on the explanation of photoelectric effect was awarded to:

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Max. Planck

Maxwell

Bohr

Rutherford

None of these

If the radius of first orbit of hydrogen atom is 0.53° A the radius of second orbit will be

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2.120°A

0.212°A

21.2°A

0.14°

a

When a platinum wire is heated, it appears dull red at about

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500°C

900°C

1100°C

1300°C

The energy of photon 'E' is proported to

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The magnetic field H

The electric field E

Both the electric and magnetic field H and E

Frequency

If A represents linear momentum and c, the velocity of light, then unit of pc in international system of units is:

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Newton

Joule

Joule-Sec

Joule-s^-1

Watt

Compton derived an expression to find compton shift by applying to the process, the law of conservation of:

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Energy only

Momentum only

Mass only

Charge only

Both (A) and (B)

Practically the quantity v/c is always:

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less than one

Equal to one

Greater then one

all of these

None of these

The special theory of relativity is based on:

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Four postulates

Three postulates

Two postulates

One postulate

None of these

The year when A.H. compton was awarded Nobel Prize is:

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1923

1927

1931

1935

None of these

As compared to the distance measured by an observer on Earth, the distance from Earth to a star measured by an observer in a moving spaceship would seem:

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Smaller

Lerger

Same

Much larger

None of these

A particle of mass 5.0 mg moves with a speed of 8.0 m/s. Its de-Brogile wavelength is

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1.66 m

1.66 x 10^-10m

1.66 x 10^-29cm

1.66 x 10^-29m

the symbol to be used in relativity problems denotes:

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Dilated time

Proper time

Life time

Half time

None of these

An electron is accelerated through a potential difference of 50v. its de-Brogile wavelength is

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1.66 x 10^-29m

1.74 x 10^-10cm

17.4 x 10^-6m

1.74 x 10^-10m

Wien's constant is measured in:

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Metre per kelviin

Metre kelvin

Kelvin per meter

Joules

Dynes

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Physics ECAT Pre Engineering Chapter 19 Dawn of Modern Physics Physics Online Test MCQs With Answers

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