Before the invention of geostationary satellites, television stations could not transmit their programmes to far off places because
these signals are electromagnetic in nature
these are not electromagnetic in nature
their wavelength is very large
they are not reflected by the ionosphere but pass through it
Correct Answer :
D. they are not reflected by the ionosphere but pass through it
Related Questions
Electromagnets are used in
the telephone ear piece
the telegraph
the electric bell
All the above
It is difficult to bon potatoes at the top or a mountain because
the water available is hard
it is colder than at sea level
the potatoes become hard
the boiling point of water is lower at that height on account of low atmospheric pressure
The temperature of a large bucket-full of hot water (a few degrees below boiling point) is lower than a beaker full of boiling water. But
the hot water contains a much larger quantity of internal energy than the boiling water
the boiling water contains more quantity of internal energy than the warm water
both of them have got the same amount of internal energy.
nothing can be said definitely with the data given
The device for tracking and locating the position of a moving object in space is called
Space ship
Lunar module
Radar
Rocket
Choose the correct answer
Microphone converts sound energy into electrical energy.
Electric fan converts electrical energy into mechanical energy.
Battery converts chemical energy into electrical energy.
All the above
The mirage is a phenomenon
generally considered as a desert happening
caused by unequal heating of the several layers of the atmosphere above the desert
in which the refracted rays take a curved path resulting in total internal refection
All the above
Credit for starting Space Science Research in India goes to
HJ Bhabha
SS Bhatnagar
V Sarabhai
CV Raman
At temperature near OK, (zero kelvin) metals such as lead and tin become
insulators
semiconductors
superconductors
condenser
The principle on which a Jet engine works is
conservation of mass
Newtonian law of action and reaction
conservation of angular momentum
None of the above
In a refrigerator cooling is produced by
the ice that deposits on the freezer
the evaporation of a volatile liquid
None of the above
Both (a) and (b)
The pressure of air at high altitude is less than the atmospheric pressure at the sea level. Hence the boning point of water at a hill top
is more than at sea level
is equal to that sea level
is less than at sea level
depends on the surrounding temperature
The force of attraction or repulsion between two charged bodies is directly proportional to the product of the charges and inversely proportional to the square of distance between them. This was propounded by
Coulomb
Gilbert
Volta
Rutherford
The strength of an electromagnet can be increased by
increasing the length of the coiled wire
increasing current supply
increasing the size of the iron core
All the above
An ammeter has
a high resistance
a very low resistance
no resistance at all
resistance of 400 ? w
For accurate scientific work, temperatures are often measured by
mercury thermometers
alcohol thermometers
platinum resistance thermometers
thermoelectric thermometers
When we tighten the string of a sitar or tanpura its pitch
remains the same
increases
decreases
None of the above
If a band is played on the moon the sound will
reverberate
be heard by us faintly
be heard upto 10 km from it
not be heard at any distance at all from it
An ohm is a unit of
potential difference
resistance
current
All the above
Frictional force acts in
the same direction as the motion
the opposite direction of the motion
all the directions
upward direction
The property of a fluid by which it resists relative motion within itself is known as
cohesive force
surface tension
diffusion
viscosity
The SI unit of electric current is
the ampere
the volt
the ohm
the coulomb
A wire conveying a current deflects a pivoted magnetic needle. This was discovered by
Marconi
Oersted
Faraday
Ohm
A ship sailing from a river to the sea
sinks less in the sea
sinks more in the sea
neither sinks more nor less in the sea
sinking more or less depends on sea
The best estimates of the age of the earth comes from the studies of
angle of inclination of the earth
changes in radio-active minerals in it
period taken by Sun's light to reach the earth
artificial satellites revolving round the earth
Warm air will hold more water vapour than cold air because
it is lighter
it has more water vapour in it
its molecules are close together
its molecules are far apart
X-rays were discovered by
Wilhelm Roentgen
WO Coolidge
Henry Cavendish
William Watson
Halley's comet appears in the heavens once in
40 years
50 years
76 years
80 years
A rheostat is used
to increase the current flow in a circuit
to decrease the current flow
to measure the flow of electric current
Either (a) or (b) above
The electroplating of a metallic article
protects the article from atmospheric corrosion
gives it a more attractive appearance
Both (a) and (b) above
None of the above
The theory that the earth constituted the centre of the universe around which the sun and the planets revolved was propounded by
Copernicus
Ptolemy
Newton
Kepler