The plants in a greenhouse are enclosed in a glass enclosure because
glass allows the heat radiations of shorter wavelengths from the sun to pass through
the plants absorb them - these shorter wavelengths - and reradiate them in the form of longer wavelengths
the longer wavelengths cannot penetrate through the glass walls
All the above
Correct Answer :
D. All the above
Related Questions
At what temperature do the Fahrenheit and Celsius scales give the same reading?
212°
32°
-40°
0°
The attraction of unlike molecules at the common surface is known as
adhesion
cohesion
surface tension
capillarity
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
The planet that moves fastest around the sun is
Mars
Venus
Earth
Mercury
A tube light works on the principle of
chemical, heating and magnetic effects of electricity
discharge of electricity through gases
the action of ultraviolet radiation on certain fluorescent materials
Both (b) and (c) above
Hydrophone is an instrument used
for measuring relative density of liquids
by ships to pass on messages
for determining the depth of ocean bottoms etc.
by deaf people to aid hearing
A piece of ice is Boating In water kept in a beaker. When all the ice melts the level of water will
first rise and then fall
fall
remain the same
rise
How is it that Pluto is not always the farthest planet of the solar system?
Each planet becomes the farthest planet in its turn. Now it is the turn of Piuto
The Sun is now in the zodiac in which it is nearest to outer planets
The eccentricity of Piuto's orbit being substantial, this orbit cuts the orbit of Neptune
Piuto belongs to other solar system
Air pressure is usually highest when the air is
warm and moist
cool and dry
warm and dry
cool and moist
Light from the sun reaches the earth in
2 minutes
4 minutes
12 minutes
8 minutes
The temperature, surface features, length of days and nights of a planet depend on
its atmosphere
its distance from the sun
its rotation
All the above
The acoustical quality of a room depends on
the size and shape of the room
the ability of the ceiling, walls and floor to exclude unwanted sound
the use of furnishings made of sound absorbing materials
All the above
The speed of sound in air at 0° C is approximately
4 x 108 m/s
1500 m/s
330 m/s
500 m/s
A radio set that uses valves does not start operating immediately when it is switched on whereas a set containing only tranaistors operates immediately. The reason for this is that
the valve filaments have low resistance
valve-radio sets work at a higher voltage
transistor set has a low resistance
filaments of the valves cake time to beat up and function
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
The colour of a star is an indication of its
distance from the earth
age
temperature
size
The function of a moderator in a nuclear reactor is
to absorb unwanted neutrons
to slow down the fast neutrons to secure more effective hits on other nuclei
to decrease the number of fissile nuclei
to increase the number of fissile nuclei
Astigmatism, a structural defect of the eye, is due to
the eye lens being thin
the eye lens being thick
lack of symmetry in the curvature of the eye preventing rays of light from being brought to a common focus
the pupil being very small
The filament lamp is an example for
fluorescence
incandescence
both (a) and (b)
None of these
The device for tracking and locating the position of a moving object in space is called
Space ship
Lunar module
Radar
Rocket
One finds it more difficult to walk on ice than on a concrete road because
there is more friction on ice than on concrete surface
ice is soft and spongy while concrete is hard
the friction between ice and the feet is less than that between the concrete and the feet
None of them
The radiator in a car serves to
cool the engine
heat up the engine
start the car
moderate the speed
A temperature below absolute zero for an ideal gas
cannot be attained experimentally
can be attained
is impossible
Does not exist at all
The base of an electric iron is brightly polished mainly
to make it smooth and frictionless
to make it rust - proof
to reduce heat loss by radiation
to make it more durable
A bar magnet tied in the middle with a thread is suspended at the South Pole of the earth. The magnet will be in
a horizontal position
a nearly vertical position with its South Pole downwards
a nearly vertical position with its North Pole downwards
a slanting position
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
The escape velocity of a satellite projected from the surface of the earth is independent of
the mass of earth
the mass of the satellite
the radius of the earth
gravitation of the earth
The speed at which light travels in vacuum is
3 x 107 ms-1
5 x 108 ms-1
3 x 104 kms-1
3 x 108 ms-1
One can be recognised by his voice alone due to the factor of
quality
amplitude
pitch
loudness
The mixing up of two gases as a result of random motion of molecules is called
diffusion
effusion
vaporisation
sublimation