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
The stars that shine brightly then dimly and then brightly are known as
meteors
binaries
variable stars
bright stars
Which of the following sets of elementary particles have nearly equal masses?
Neutron and Proton
Electron and Proton
Neutron and Electron
Proton, Neutron and Electron
In a vacuum the following three articles are dropped at the same time and from the lame height. Which will reach the ground quicker?
a stone
a piece of wood
a feather
all will reach the ground at the same time
The device for tracking and locating the position of a moving object in space is called
Space ship
Lunar module
Radar
Rocket
On applying a constant force to a mass, It moves with a uniform
velocity
momentum
acceleration
angular velocity
The velocity of sound in air
increases as the square root of the absolute temperature
decreases with temperature
is independent of temperature
None of these
Metals are good conductors of heat because
they contain free electrons
their atoms are relatively far apart
their atoms collide frequently
they have reflecting surfaces
Mercury is used in a barometer because
its density being very high 13.6 g/cm3 the height of mercury column is conveniently small
at the ordinary temperature its vapour pressure is small
it is opaque and does not wet glass
All the above
In the electrical circuit of a house the fuse acts as
a thermopile
a load
a step down device
a safety device
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
While crossing a suspension bridge, the soldiers are ordered to break steps because
the marching in steps will involve a big strain on them
the resonant vibrations caused by their marching can damage the bridge increasing the amplitude to dangerous proportions
the marching may obstruct other traffic
rumblings of their marching may disturb the surroundings
If a body is taken from the earth to the moon
both its mass and weight will be different
its mass will be different but the weight will remain the same
its mass and weight will both remain unchanged
its mass will remain the same but weight will be different
If an empty cylinder Is half ruled with a liquid, Its centre of gravity is
shifted upwards
shifted downwards
shifted neither upward nor downward
shifted upward or downward depending on the density of the liquid
Why is it cool near an open pond on a hot summer day?
Evaporation at the surface causes cooling
The heat obsorbed at the surface is passed on to the bottom
Because of impurity in the water
Because of convection currents set up inside water
In hot climatic conditions, the buildings are painted white because
white paint is economical
it does not fade off
it does not crack with higher temperature
white coating is a bad conductor of heat and reflects heat rays that fall on it, thus keeping the inside cool
The device used to record the sound is
a microphone
a headphone
a phonograph
an amplifier
A lightning conductor installed in a building
does not allow the lightning to fall on the building at all
drives away the charged clouds
forces the lightning to fall on other buildings near that building
conducts the electric charges to the ground when lightning strikes the building
The maximum displacement of the particle in a mechanical wave motion is known as
amplitude
vibration
frequency
phase
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
Skating on ice is possible because
the surface of ice is smooth
ice is cold
the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
the pressure on the ice due to skate raises its melting point
The planet that has got a well-developed set of rings is
Venus
Saturn
Mercury
Earth
What la the minimum velocity required for a rocket to overcome earth's gravity and travel into space?
18 km/sec
11.2 km/ sec
21 km/ sec
35 km/ sec
Every action has an equal and opposite reaction is Newton's law of Motion
first
second
third
fourth
The function of a ruse wire is
to stabilise the voltage
to decrease the current supply
to increase the current supply
to prevent an unduly high current from passing through a circuit
A cyclist leans inwards when he is negotiating a curve 10 that
he may increase his speed
his weight may be reduced
necessary centripetal force may be available from the horizontal component of the normal reaction due to the track to maintain the curved motion
no frictional force may be produced between the wheels and the axle
In the nucleus of an atom, the uncharged particle is
proton
neutron
electron
positron
Drinks kept in a vacuum flask remain hot or cold as the case may be for a long time because
both walls are silvered on the vacuum side
there is vacuum between the double walls
the cork is a poor conductor of heat
of all the above
Gamma radiations are used for
sterilising food stuff
controlling pests
cancer therapy
All of these
The rocket engine is motivated by jet propulsion which uses the famous
Kepler's Laws
Newtonian Third Law of Motion
Bernoulli's Principle
Law of Relativity
The speed of sound in a medium depends upon the properties of the medium such as
its density
its temperature
its elasticity
All the above