11. The special technique used in ships to calculate the depth of ocean beds is

1. 1. LASER

   
   
   

   2. SONAR

   
   
   

   3. sonic boom

   
   
   

   4. reverberation

   
   
   

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1. View Hint View Answer Discuss in Forum

   SONAR

   Correct Option: B

   SONAR

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12. Solar energy is produced by the following reaction

1. 1. Fission reaction

   
   
   

   2. Fusion reaction

   
   
   

   3. Chemical reaction

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Fusion reaction

   Correct Option: B

   Fusion reaction

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13. Einstein got noble prize for

1. 1. Photoelectric effect

   
   
   

   2. Compton effect

   
   
   

   3. Theory of relativity

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Photoelectric effect

   Correct Option: A

   Photoelectric effect

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14. Light year is

1. 1. Light emitted by the sun in one year

   
   
   

   2. Time taken by light to travel from sun to earth

   
   
   

   3. The distance travelled by light in free space in one year

   
   
   

   4. Time taken by earth to go once around the sun

   
   
   

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1. View Hint View Answer Discuss in Forum

   1 light year = speed of light in vacuum x no.
   of seconds in one year = (3 x 10⁸) x (365 x 24 x 60 x 60) = 9.467 x 10¹⁵ m.

   Correct Option: C

   1 light year = speed of light in vacuum x no.
   of seconds in one year = (3 x 10⁸) x (365 x 24 x 60 x 60) = 9.467 x 10¹⁵ m.

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15. The number of electrons in an atom of atomic number Z and mass number A is

1. 1. Z

   
   
   

   2. A

   
   
   

   3. A - Z

   
   
   

   4. none

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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