General Science Questions (MCQs) for Competitive Examinations
General Science Multiple choice questions for GK paper in SSC, NDA, CDS, UPSC, UPPSC and State PSC Examinations.
31. Which of the following are the areas of application of Doppler’s effect?
[A] At airports to guide aircraft
[B] in the military to detect enemy aircraft
[C] Sonography
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
The change in frequency caused by a moving object due to Doppler effect is used to measure their velocities in diverse areas. It is used by police to check over-speeding of vehicles. It is used at the airports to guide aircraft, and in the military to detect enemy aircraft. Doctors use it to study heart beats and blood flow in different parts of the body. Here they use ultrasonic waves, and in common practice, it is called as sonography.
32. What do we call the distance between two consecutive compressions of a sound wave?
[A] Wave number
[B] Frequency
[C] Wavelength
[D] Amplitude
Show Answer
Correct Answer: C [Wavelength]
Notes:
The distance between two consecutive compressions (C) or two consecutive rarefactions (R) is called the wavelength.
33. What is supersonic speed?
[A] When the speed of any object exceeds the speed of sound
[B] When the speed of any object exceeds the speed of light
[C] When the speed of any object exceeds 10000 m/s
[D] None of the above
Show Answer
Correct Answer: A [When the speed of any object exceeds the speed of sound]
Notes:
When the speed of any object exceeds the speed of sound it is said to be travelling at supersonic speed. Bullets, jet aircrafts etc. often travel at supersonic speeds.
34. Which of the following is true about a concave lens?
[A] power of a concave lens is positive
[B] power of a concave lens is negative
[C] power of a concave lens is zero
[D] None of the above
Show Answer
Correct Answer: B [power of a concave lens is negative]
Notes:
The power of a convex lens is positive and that of a concave lens is negative.
35. Which of the following phenomenon is the basis of an electric generator?
[A] Electromagnetic Induction
[B] Ferroelectric effect
[C] Telluric currents
[D] Electroluminescence
Show Answer
Correct Answer: A [Electromagnetic Induction]
Notes:
In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity.
36. Which of these diodes convert electrical energy into light?
[A] Photodiodes
[B] Light emitting diodes
[C] Photovoltaic devices
[D] None
Show Answer
Correct Answer: B [Light emitting diodes]
Notes:
Light emitting diodes (LED) are special diodes which convert electrical energy into light.
37. Which of the following is correct about conductors?
[A] The conduction band and the valence band partly overlap each other
[B] There is no forbidden energy band gap between conduction band and the valence band
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: C [Both a and b]
Notes:
The conduction band and the valence band partly overlap each other and there is no forbidden energy band gap in between. The electrons from the valence band can easily move into the conduction band. Hence, large number of electrons are available for conduction.
38. Which of the following is the purest form of Iron?
[A] Pig iron
[B] Cast iron
[C] Wrought iron
[D] None of the above
Show Answer
Correct Answer: C [Wrought iron]
Notes:
Wrought iron is the purest form of iron. Pig iron has about 4% of carbon and some other impurities. Cast iron has about 3% of carbon content.
39. What do we call the difference between the initial mass energy and the total mass energy of the decay products in a radioactive decay?
[A] entropy
[B] disintegration energy
[C] alpha energy
[D] integration energy
Show Answer
Correct Answer: B [disintegration energy]
Notes:
The disintegration energy or the Q-value of a nuclear reaction is the difference between the initial mass energy and the total mass energy of the decay products.
40. What is the shape of SF4 molecule?
[A] Bent
[B] See-saw
[C] Trigonol Pyramidal
[D] T-shape
Show Answer
Correct Answer: B [See-saw]
Notes:
SF4 molecule is see-saw in shape. It has 4-bonding pairs of electrons and one lone pair of electrons.
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