Echoes are produced by
the reflection of sound waves
the refraction of sound waves
the interference of sound waves
reverberation of sound waves
Correct Answer :
A. the reflection of sound waves
Related Questions
A transformer
converts direct current into alternating current
converts alternating current into direct current
steps up or steps down a given alternating current voltage
supplies current with zero resistance
The SI unit of electric current is
the ampere
the volt
the ohm
the coulomb
SONAR (Sound Navigation Ranging) is
used by warships and military aircraft to locate enemy submarines
used by ships to determine the depth of water beneath them
a detective device that uses sound to locate under - water objects
All the above
Some persons are not able to see distant objects clearly because the image of the object is focused in front of the retina. This defect is known as
short sight
long sight
astigmatism
presbyopia
A person does not sink in the Dead Sea because
the sea contains a large amount of other salts besides sodium chloride
the density of the person is less than the density of the Dead Sea water
of the surface tension due to salt water in the Dead Sea
of difference in mass
Chronometer is an instrument to measure
heat
electric potential
time
distance between two points
The velocity required to place a vehicle in orbit round the moon is _________ that required to place it in orbit round the earth.
less than
greater than
equal to
greater than or equal to
Sound waves In 'air travel faster if
frequency is higher
wavelength is smaller
pitch is smaller
air is warmer
Radio waves sent out by radio stations are reflected by
troposphere
stratosphere
mesosphere
ionosphere
The rings of Saturn were discovered by
Galileo
Bhaskara
Aryabhatta
Ptolemy
A man weighing 50 kg floats on water in a lake. His apparent weight is
50 kg
45 kg
zero
150 kg
When a steel ball is placed on the surface of mercury, it does not sink because
of the surface tension of mercury
mercury is a semi-solid
of the high viscosity of mercury
the density of mercury is greater than that of steel
A cup of hot coffee is placed on a metal table in a room. By which of the following methods does it lose heat?
conduction and convection only
conduction and radiation only
convection and radiation only
conduction, convection and radiation
A boy sitting in a train moving with a uniform velocity drops a coin outside. A man standing outside the train will find the trajectory of the coin to be
a parabola
a horizontal straight line
a vertical straight line
a circle
A projectile is fired at an angle with the horizontal with a small velocity. Its horizontal range will be maximum when the angle with the horizontal is
0°
30°
45°
60°
When a ship floats on water, the weight or water displaced is
an indeterminate quantity
equal to the weight of the ship
greater than the weight of the ship
less than the weight of the ship
A spherical mirror is
a reflecting elliptical portion
a reflecting spherical surface
a parabolic reflecting surface
a flat reflecting surface
The image of an object formed in a plane mirror
is real
is virtual
can be obtained on a screen
is slightly bigger than the object
Changing of one element into another element is known as
transmutation
fission
fusion
radioactivity
When ice melts, Its volume
decreases
increases
remains the same until all the ice has melted and then increases
remains the same
Sound waves in air are
transverse
longitudinal
transverse and longitudinal
neither transverse nor longitudinal
The principle of equivalence of mass and energy was established by
Dalton
Rutherford
Einstein
Planck
A hydrogen bomb is based on
nuclear fusion
nuclear fission
Both (a) and (b) above
Neither (a) nor (b)
Which force is used when milk is churned to separate cream?
cohesive
centrifugal
frictional
gravitational
The speed of light is minimum while passing through
air
glass
vacuum
water
If a body weight 12N on the surface of the earth, how much will it weigh on the surface of the moon where acceleration due to gravity is only one-sixth of that on earth's surface?
12N
2N
10N
6N
Air pressure is usually highest when the air is
warm and moist
cool and dry
warm and dry
cool and moist
The atmosphere gets heated up mainly by
direct sun's rays
radiation from earth's surface
radiogenic heat (resulting from radioactive decay)
cosmic rays coming from space
The motion .of the pendulum of a wall clock is an example of
linear motion
vibratory motion
rotational motion
None of the above
The Space Application Centre for training in Satellite Communication Technology is located at
Bangalore
Mumbai
Ahmedabad
New Delhi