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Modern Physics

97 MCQ questions with answers and explanations · page 4 of 4

Test yourself▶ 25 question test▶ 50 question test

Q76. Otto Hahn discovered the atomic bomb on the basis of the following principle:

  1. Auranium fission
  2. Bnuclear fission
  3. Calpha radiation
  4. Dgamma radiation
Show answer & explanation

Answer: A) uranium fission

Q77. 'Laser' is a device which is produced by-

  1. Aspontaneous radiation
  2. BDispersed radiation
  3. Cscattered radiation
  4. DStimulated radiation
Show answer & explanation

Answer: D) Stimulated radiation

Q78. Cryogenic engines are used in—

  1. Ain the rocket
  2. Bin a nuclear reactor
  3. Cin frosted refrigerators
  4. Din research on superconductivity
Show answer & explanation

Answer: A) in the rocket

Q79. When the TV is switched on, then-

  1. ABoth audio and video start simultaneously
  2. BThe audio is played immediately, but the visual is played later, as the scene requires some practice time.
  3. CThe visuals begin immediately, but the audio is heard later because sound travels slower than light.
  4. DIt depends on the brand of the TV.
Show answer & explanation

Answer: C) The visuals begin immediately, but the audio is heard later because sound travels slower than light.

Q80. The waves used in radar systems are….

  1. Ainfrared
  2. Bradio
  3. CUltraviolet
  4. DMicro
Show answer & explanation

Answer: D) Micro

Q81. The source of inexhaustible energy in stars is due to-

  1. Aconversion of hydrogen into helium
  2. Bconversion of helium into hydrogen
  3. Cdecay of radioactive substances
  4. DAn abundance of oxygen that helps in combustion and produces energy
Show answer & explanation

Answer: A) conversion of hydrogen into helium

Q82. By what can the penetrating power of X-rays be increased?

  1. Aincreasing the current in the filament
  2. BDecreasing the potential difference between the cathode and anode
  3. Cby reducing the current in the filament
  4. Dincreasing the potential difference between the cathode and the anode
Show answer & explanation

Answer: D) increasing the potential difference between the cathode and the anode

Q83. Who invented the first thermionic valve?

  1. AThomas Edison
  2. BRichardson
  3. CJ. A. Fleming
  4. DLee D. Forest
Show answer & explanation

Answer: C) J. A. Fleming

Q84. In a laser, all the atoms emit light waves.

  1. Aof the same frequency
  2. Bof the same dimension
  3. Cof the same phase
  4. DAll of the above
Show answer & explanation

Answer: D) All of the above

Q85. The electromagnetic waves used for satellite communication are-

  1. Ainfrared radiation
  2. Bultraviolet radiation
  3. Cradio waves
  4. Dvisible light
Show answer & explanation

Answer: C) radio waves

Q86. 'Super conductors' are substances which are-

  1. Awhich offers the least resistance to the flow of electric current
  2. Bwhich conduct electricity at low temperatures
  3. Cwhich conduct electricity at high temperatures
  4. DWhich provide high resistance to the flow of electric current.
Show answer & explanation

Answer: A) which offers the least resistance to the flow of electric current

Q87. Which of the following is not an electromagnetic wave?

  1. AX-rays
  2. BLight
  3. Cultrasonic waves
  4. Dthermal radiation
Show answer & explanation

Answer: C) ultrasonic waves

Q88. What is the conductivity of a superconductor?

  1. AUnlimited
  2. BLess
  3. CZero
  4. DMore
Show answer & explanation

Answer: A) Unlimited

Q89. Photovoltaic cells are-

  1. ASolar Cell
  2. BThermal Cell
  3. CSulfur Cell
  4. Dmolar cell
Show answer & explanation

Answer: A) Solar Cell

Q90. Einstein was awarded the Nobel Prize for-

  1. Afor photoelectric effect
  2. BFor the theory of specific heats
  3. CFor the special theory of relativity
  4. Dfor Bose-Einstein statistics
Show answer & explanation

Answer: A) for photoelectric effect

Q91. Which of the following types of radiation has the shortest wavelength?

  1. Aradio waves
  2. Bvisible light
  3. CInfrared
  4. DUltraviolet
Show answer & explanation

Answer: D) Ultraviolet

Q92. Which of the following types of radiation has the shortest wavelength?

  1. Aradio waves
  2. BUltraviolet
  3. CInfrared
  4. Dvisible light
Show answer & explanation

Answer: B) Ultraviolet

Q93. The electromagnetic waves used for satellite communication are-

  1. Ainfrared radiation
  2. Bultraviolet radiation
  3. Cradio waves
  4. Dvisible light
Show answer & explanation

Answer: C) radio waves

Q94. Which one of the following is not a property of X-rays?

  1. AThey are deflected by electric fields
  2. BThey are not deflected by magnetic fields.
  3. CTheir penetration length in liquid is large.
  4. DTheir wavelength is much shorter than that of visible light.
Show answer & explanation

Answer: A) They are deflected by electric fields

Q95. Which of the following statements is not correct regarding ultraviolet light?

  1. AIt is an electromagnetic wave
  2. BIts wavelength is smaller than that of visible light.
  3. Cit is a longitudinal wave
  4. DIt can move in vacuum
Show answer & explanation

Answer: C) it is a longitudinal wave

Q96. The resistance of a semiconductor when heated is-

  1. Aincreases
  2. Bdecreases
  3. Cremains the same
  4. DFirst increases and then decreases. (e) None of the above / More than one of the above
Show answer & explanation

Answer: B) decreases

Q97. According to the special theory of relativity, which of the following is not relative?

  1. Acontemporaneity
  2. Bspeed of light
  3. Clength of an object
  4. Dtime interval between two events
Show answer & explanation

Answer: B) speed of light

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