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4

A workman was working on a rail track. A young boy at a distance holds his ear close to the railway track. The boy was able to hear the sound of each blow or the workman twice. It is because

A. speed of sound is greater in steel than in air

B. speed of sound is greater in air than in steel

C. part of sound waves is reflected between rail tracks

D. the boy's ears are at a different distance from the source

Correct Answer :

A. speed of sound is greater in steel than in air


Related Questions

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Sound waves In 'air travel faster if

A. frequency is higher

B. wavelength is smaller

C. pitch is smaller

D. air is warmer

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When a light ray is reflected repeatedly by a set of parallel plane mirrors, the intensity of light ray diminishes alter a few reflections. This is because of

A. poor reflection from the mirrors

B. scattering of light from the mirrors

C. absorption of some light by the mirrors

D. absorption of light by the atmosphere

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4

When a ship floats on water, the weight or water displaced is

A. an indeterminate quantity

B. equal to the weight of the ship

C. greater than the weight of the ship

D. less than the weight of the ship

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4

Which mirror is used as a rear view mirror in Vehicles?

A. Parabolic

B. Convex

C. Concave

D. Plain

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4

The characteristics of a musical note are

A. loudness

B. pitch

C. quality or timbre

D. All the above

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4

The resistance of a wire depends on

A. the material of the wire

B. the length of the wire

C. the cross section of the wire

D. All the above

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4

The neutron, one of the constituent particles of which the nuclei of atoms are composed was discovered by

A. Irene Curie

B. W Bothe and H Becker

C. James Chadwick

D. Jean Joliot

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The colour of the light which travels through glass with minimum speed is

A. red

B. violet

C. green

D. yellow

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Stars twinkle because of

A. refraction of light from them through air

B. reflection

C. absorption

D. All the above

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4

When a body is projected upwards

A. the time for the upward journey and downward journey are the same

B. the upward journey takes more time

C. the downward journey takes more time

D. Can't be said

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4

The leader of the team who succeeded in constructing the first nuclear reactor (an atomic pile) in the world was

A. Albert Einstein

B. Enrico Fermi

C. HJ Bhabha

D. Sir Isaac Newton

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4

Formation of shadows can be explained by

A. rectilinear propagation of light

B. reflection

C. refraction

D. total internal reflection

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The velocity required to place a vehicle in orbit round the moon is _________ that required to place it in orbit round the earth.

A. less than

B. greater than

C. equal to

D. greater than or equal to

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Electromagnets are used in

A. the telephone ear piece

B. the telegraph

C. the electric bell

D. All the above

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4

A workman was working on a rail track. A young boy at a distance holds his ear close to the railway track. The boy was able to hear the sound of each blow or the workman twice. It is because

A. speed of sound is greater in steel than in air

B. speed of sound is greater in air than in steel

C. part of sound waves is reflected between rail tracks

D. the boy's ears are at a different distance from the source

What is the correct answer?

4

Mercury is used in a barometer because

A. its density being very high 13.6 g/cm3 the height of mercury column is conveniently small

B. at the ordinary temperature its vapour pressure is small

C. it is opaque and does not wet glass

D. All the above

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4

A light year means

A. a unit of time

B. a unit of length

C. a year of no consequence

D. illumination throughout the year

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4

In the nucleus of an atom, the uncharged particle is

A. proton

B. neutron

C. electron

D. positron

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In a microphone

A. sound energy is converted into electrical energy

B. electrical energy is converted into sound energy

C. sound energy is converted into mechanical energy

D. mechanical energy is converted into sound energy

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4

In an oil lamp, holes are provided below the chimney so that

A. necessary oxygen for burning of oil may be provided

B. the convection current of air may be maintained to keep the lamp burning

C. the brightness of the lamp may be increased

D. All the above

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4

When a ship floats on water, the weight or water displaced is

A. an indeterminate quantity

B. equal to the weight of the ship

C. greater than the weight of the ship

D. less than the weight of the ship

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4

The motion .of the pendulum of a wall clock is an example of

A. linear motion

B. vibratory motion

C. rotational motion

D. None of the above

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4

In experiments on static electricity the standard method for obtaining small amounts of positive electricity is to rub

A. a glass rod with flannel

B. an abonite rod with flannel

C. a glass rod with silk

D. Any of the above

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4

When one enters a dark room after being in bright light one is not able to see anything clearly for a while because

A. the retina of the eye moves forward

B. the retina of the eye moves backward

C. c).the iris is unable to dilate the pupil immediately to be able to see things

D. the eye has no power of accommodation

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4

A permanent magnet may be demagnetised by

A. placing it inside a solenoid through which an alternating current is flowing

B. heating the magnet to redness and then allowing it to cool

C. dropping it several times or hammering it while lying east-west

D. All the above

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The image of an object formed in a plane mirror

A. is real

B. is virtual

C. can be obtained on a screen

D. is slightly bigger than the object

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In a river, the currents are fastest where the river la

A. wide and shallow

B. narrow and shallow

C. wide and deep

D. narrow and deep

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The transistor was invented by

A. Marconi

B. Baird

C. John Bardeen, Walter H. Brattain and William Shockley

D. Edison

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The planet that moves fastest around the sun is

A. Mars

B. Venus

C. Earth

D. Mercury

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The mirage is a phenomenon

A. generally considered as a desert happening

B. caused by unequal heating of the several layers of the atmosphere above the desert

C. in which the refracted rays take a curved path resulting in total internal refection

D. All the above