16. The absolute charge of an electron is

1. 1. (-1.6) x 10^-19 C

   
   
   

   2. (+ 1.6) x 10⁺¹⁹ C

   
   
   

   3. 1.6 x 10^-19 C

   
   
   

   4. None of these

   
   
   

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   NA

   Correct Option: A

   NA

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17. Which of the following has highest frequency ?

1. 1. Cosmic rays

   
   
   

   2. X - rays

   
   
   

   3. Radio waves

   
   
   

   4. Micro waves

   
   
   

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   NA

   Correct Option: A

   NA

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18. Which of the following electromagnetic wave has the longest wave length ?

1. 1. Infra red rays

   
   
   

   2. Gamma rays

   
   
   

   3. Light rays

   
   
   

   4. Ultra-violet rays

   
   
   

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   NA

   Correct Option: A

   NA

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19. Consider the following pairs of ions or atoms
    1. Na⁺ and NC
    2. Na⁺ and K⁺
    3. K⁺ and C^-
    In which of these pair are the ions/atoms iso-electronic with each other ?

1. 1. 1, 2 and 3

   
   
   

   2. 1 and 2

   
   
   

   3. 2 and 3

   
   
   

   4. 1 and 3

   
   
   

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   NA

   Correct Option: D

   NA

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20. An atom has 7 electrons in its M-Shell and contains 18 neutrons in its nucleus. What is its mass number ?

1. 1. 25

   
   
   

   2. 27

   
   
   

   3. 35

   
   
   

   4. 43

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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