Top 100 Physics General Knowledge Questions and Answers

1. Which mirror is to be used to obtain a parallel beam of light from a small lamp ? – Concave mirror
2. The focal length of the lens in a photographic camera is 5 cm. What is the power of the lens? – + 20 D
3. When viewed in white light, why do soap bubbles show colours? – Because of interference
4. Angular separation between two colours of the spectrum depends upon which thing? – Angle of deviation
5. Total internal reflection of light is possible when light enters from which thing? – Water to air
6. Which is used to remove astigmatism for a human eye? – Cylindrical lens
7. Why does diffusion of light in the atmosphere take place? – Due to dust particles
8. Which phenomena can not be attributed to the refraction of light? – Redshift
9. Total internal reflection can take place when light travels from which thing? – Diamond to glass
10. The refractive index of a given piece of transparent quartz is greatest for which light? – Violet light
11. A virtual image larger than the object can be formed by which mirror? – Concave mirror
12. If there were no atmosphere, what will be the length of the day on the earth? – Decrease
13. The focal length of a convex lens is 50 cm. what is its power? – +2 D
14. For an astronaut in a space ship, how does the sky appear? – Black
15. Which phenomena is used in optical fibres? – Total internal reflection
16. What is the phenomenon of splitting white light into seven colours? – Dispersion
17. Critical angle is minimum when a light ray passes which thing? – Glass to air
18. If the angle between two plane mirrors is 60°; then how many number of image will be formed? – 5
19. In which part of the eye lies the pigment, that decides the colour of the eyes of a person? – Choroid
20. Critical angle of. light passing from glass to water is minimum for which colour? – Violet colour
21. To an observer on the lunar surface, during the day time, how will the sky appear? – Black
22. What is the unit of luminous efficiency of an electric bulb? – Lumen / watt
23. Which of light are strongly absorbed by plants? – Blue and red
24. A far-sighted person has a near point at 100 cm. What must be the power of the correcting lens? – +3.0 D
25. How many image can a man see if he stands between two plane mirrors inclined at an angle of 60°? – 5
26. How is image formed on the retina of a human eye? – Real and inverted
27. The resistance of material increases with temperature. What is this? – Metal
28. When do all the magnetic materials lose their magnetic properties? – Strongly heated
29. What is the relative permeability of a paramagnetic material? – Greater than unity
30. A soap bubble is given negative charge then what happen in its radius? – Increases
31. How is the relative permeability of a diamagnetic material? – Less than unity
32. How are the magnetic field lines in the middle of a solenoid? – Parallel to the axis
33. Why do Electricians use rubber gloves while working? – Rubber is an insulator
34. What work is work done in moving a positive charge on an equipotential surface? – Zero
35. Kirchhoff’s voltage law is based on the law of conservation of which thing? – Energy

36. Why is In a hydel station the motion produced in turbines? – Due to the flow of water
37. What is most suitable for the core of an electromagnet? – Soft iron
38. At a grid sub stations the voltage is stepped up to reduce loss of which thing? – Power
39. Equal charges are given to two spheres of different radii. What will the potential be? – More on smaller sphere
40. Two electron beams are travelling parallel to each other. What will be their reactions? – Repel each other
41. Instrument used to store the electric charge is known by which name? – Capacitor
42. When an ebonite rod is rubbed with fur, which charge acquired by the fur? – Positive
43. Conversion of chemical energy into electrical energy occurs in which thing? – Battery
44. What is the temperature at which a ferromagnetic material becomes paramagnetic? – Curie temperature
45. A magnetic needle is kept in non uniform magnetic field. What does itexperiences? – A force and a torque
46. Where will be the Time period in a vibration magnetometer infinite? – At magnetic pole
47. The north pole of the earth’s magnet is near the geographical which direction? – South
48. If the current in the core decreases, what will the strength of the magnetic field be? – Decreases
49. The intensity of a magnetic field is defined as the force experienced by which pole? – Unit north pole
50. If a material, placed in a magnetic field is thrown out of it, then how is the material? – Diamagnetic
51. The capacity of a pure capacitor is 1 farad. In D.C. circuit, what will its effective resistance be? – Infinite
52. If a bar magnet is cut length wise into 3 parts, what will the total number of poles be? – 6
53. For electroplating a spoon, it is placed in the voltameter at which postion? – The position of cathode
54. A substance, when inserted between the poles of a magnet, is pushed out, what is it? – Diamagnetic
55. By inserting a soft iron piece into solenoid, what does the strength of the magnetic field? – Increase
56. The magnetic induction associated with currents flowing in a hollow copper tube, how will be? – only out side
57. How is the electric potential at the centre of a charged conductor? – Same as on the surface
58. What is not the cause of low conductivity of electrolyte? – Ionisation of salt
59. What is Electric field intensity at a point a hollow charged spherical conductor? – Is zero
60. Which property is processed by the ferromagnetic substance? – Hysterasis
61. Which type of cell can be used if a device requires 75 A of current for 15 seconds? – Lead-acid cell
62. A hydrogen atom is paramagnetic. What is a hydrogen molecule? – Diamagnetic
63. In nuclear fission, how many percentage of mass is converted into energy? – 0.1%
64. X210 has half life of 5 day. What is the time taken for seven-eights of sample of X210 to decay? – 15 days
65. If a U-238 nucleus splits into two identical parts, how will the two nuclei be so produced? – Stable
66. What is the half-life of a radioactive element which has only 1/32 of its original mass left after a lapse of 60 days? – 12 days
67. If a proton of mass m is moving with the velocity of light, what will its mass be? – Infinite
68. What was the fissionable material used in the bomb dropped at Nagasaki (Japan) in the year 1945? – Plutonium
69. Energy transferred to a person through gamma rays is measured in by which unit? – Roentgens
70. Which field is used to produce deflection in a television picture tube? – A magnetic fields
71. The electron emitted in beta radiation originates from where? – Inner orbits of atoms
72. From which the cathode ray particles originate in a discharge tube? – Cathode
73. Einstein’s mass energy relation is given by which expression? – E = mc2
74. Which rays will deflect in electric field? – Cathode rays
75. What percentage of the original quantity of a radioactive material is left after five half lives approximately? – 3%
76. What is the important conclusion given by Millikan’s experiment about the charge? – Charge is quantized
77. What are Alpha rays emitted from a radioactive substance? – Helium nuclear
78. Which are the Particles that can be added to the nucleus of an atom without changing its chemical properties? – Neutrons
79. Which particle has similar mass to that of the electron? – Positron
80. When the speed of electrons increases, then what happens in the value of the specific charge on an electron? – Decreases
81. The colour of the +ve column in a gas discharge tube depends on which thing? – The gas in the tube
82. The first explosion of an atomic device in India was carried out in which state? – Rajasthan
83. Direct conversion of solar energy with the use of photovoltaic cell results in the production of which energy? – Electrical energy
84. Why is energy is continuously generated in the sun? – Due to nuclear fusion
85. What is the ratio of specific charges of an á-particle to that of a proton? – 1/2
85. Long distance short-wave radio broad casting uses which waves? – Ionospheric wave
86. Which satellite is used in ship-to-shore and shore-to-shore and shore-to-ship communication? – Marisat
87. Which is electrical circuits used to get smooth de output from a rectified circuit called? – Filter
88. When the temperature of semiconductor is increased, what will happen in its electrical conductivity? – Increases
89. With the rise of temperature, what will happen in the specific resistance of semiconductor? – Decreases
90. The absorption of radio waves by the atmosphere depends on which thing? – Their frequency
91. Which are the space waves are affected seriously by atmospheric conditions? – UHF
92. With which can Radio wave of constant amplitude be generated? – Oscillator
93. What is the electrical circuit used to get smooth DC output from a rectifier circuit called? – Filter
94. If germanium has to be doped with a donor impurity, how should the foreign atom be? – Pentavalent
95. In a p-type semiconductor, Which are the majority charge carriers? – Holes
96. The unidirectional property of a pn-junction is useful for its use as which thing? – Rectifier
97. Which energy of the electron at absolute zero is called? – Fermi energy
98. For television broadcasting, what frequency is employed normally? – 30-300 MHz
99. A zener diode is also a p – n junction diode. It can be used as which regular?DC voltage regulator
100. Which effect shows particle nature of height? – Photoelectric effect


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