Question 31 : Light Emitting Diodes (LED) is used in fancy electronic devices such as toys emit
1. X-rays
2. ultraviolet light
3. visible light
4. radio waves
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Question 32 : Out of the following pairs, which one does not have identical dimension?
1. Moment of inertia and moment of a force
2. Work and Torque
3. Angular momentum and Planck's constant
4. Impulse and Momentum
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Question 33 : Of the following natural phenomena, tell which one known in Sanskrit as 'deer's thirst'?
1. Rainbow
2. Earthshine
3. Halo
4. Mirage
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Question 34 : Natural radioactivity was discovered by
1. Marie Curie
2. Ernest Rutherfor
3. Henri Becquerel
4. Enrico Fermi
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Question 35 : Let a thin capillary tube be replaced with another tube of insufficient length then, we find water
1. will overflow
2. will not rise
3. depressed
4. change its meniscus
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Question 36 : out of the following, which is not emitted by radioactive substance?
1. Electrons
2. Electromagnetic radiations
3. Alpha particles
4. Neutrons
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Question 37 : Light travels at the fastest speed in
1. glass
2. water
3. hydrogen
4. vacuum
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Question 38 : On a stationary sail boat, air is blown from a fan attached to the boat. The boat
1. moves in opposite direction in which the air is blown
2. does not move
3. moves in the same direction in which air blows
4. spins around
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Question 39 : Large astronomical telescopes always use as objective
1. lens
2. mirror
3. combinations of lenses
4. None of the above
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Question 40 : On a cold day when a room temperature is 15^oC, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15^oC, because
1. metals have higher thermal capacity than plastics
2. plastics have a lower density than metals
3. metals are good conductor of heat
4. plastics have a higher thermal conductivity than metals
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