36. The energy of hydrogen atom in nth orbit is E_n, then the energy in nth orbit of single ionised helium atom will be​​​

1. 1. 4E_n

   
   
   

   2. E_n/4

   
   
   

   3. 2E_n

   
   
   

   4. E_n/2

   
   
   

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1. View Hint View Answer Discuss in Forum

   We have
   

   En =	-2π2mK2Z2e4
   	n2h2

   
   For helium Z = 2. Hence requisite answer is 4E_n

   Correct Option: A

   We have
   

   En =	-2π2mK2Z2e4
   	n2h2

   
   For helium Z = 2. Hence requisite answer is 4E_n

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37. An electron changes its position from orbit n = 2 to the orbit n = 4 of an atom. The wavelength of the emitted radiations is (R = Rydberg’s constant)​​

1. 1. 	16
      	R

   
   
   

   2. 	16
      	3R

   
   
   

   3. 	16
      	5R

   
   
   

   4. 	16
      	7R

   
   
   

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1. View Hint View Answer Discuss in Forum

   V = R		1	-	1
   		n21		n22

   
   where n₁ = 2, n₂ = 4
   

   V = R		1	-	1
   		4		16

   
   

   	1	= R		12
   	λ			4 × 16

   
   

   ⇒ λ =	16
   	3R

   Correct Option: B

   V = R		1	-	1
   		n21		n22

   
   where n₁ = 2, n₂ = 4
   

   V = R		1	-	1
   		4		16

   
   

   	1	= R		12
   	λ			4 × 16

   
   

   ⇒ λ =	16
   	3R

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38. ​In which of the following systems will the radius of the first orbit (n = 1) be minimum ?

1. 1. Hydrogen atom ​

   
   
   

   2. Doubly ionized lithium ​

   
   
   

   3. Singly ionized helium​ ​

   
   
   

   4. Deuterium atom

   
   
   

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1. View Hint View Answer Discuss in Forum

   r ∝	1	;
   	Z

   
   Z(=3) is maximum for Li²⁺.

   Correct Option: B

   r ∝	1	;
   	Z

   
   Z(=3) is maximum for Li²⁺.

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39. Energy E of a hydrogen atom with principal quantum number n is given by E = – 13.6/n² eV. The energy of photon ejected when the electron jumps from n = 3 state to n = 2 state of hydrogen is approximately

1. 1. 1.9 eV.

   
   
   

   2. 1.5 eV ​

   
   
   

   3. 0.85 eV ​

   
   
   

   4. 3.4 eV

   
   
   

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1. View Hint View Answer Discuss in Forum

   ∆E = E₃ – E₂
   

   =	- 13.6	+	13.6
   	32		22

   
   

   = 13.6		1	-	1		eV = 1.9 eV
   		4		9

   Correct Option: A

   ∆E = E₃ – E₂
   

   =	- 13.6	+	13.6
   	32		22

   
   

   = 13.6		1	-	1		eV = 1.9 eV
   		4		9

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40. The Bohr model of atoms

1. 1. predicts the same emission spectra for all types of atoms ​

   
   
   

   2. assumes that the angular momentum of electrons is quantised

   
   
   

   3. uses Einstein’s photoelectric equation

   
   
   

   4. ​predicts continuous emission spectra for atoms

   
   
   

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1. View Hint View Answer Discuss in Forum

   In Bohr’s model, angular momentum is quantised i.e
   

   l = n		h
   		2π

   Correct Option: B

   In Bohr’s model, angular momentum is quantised i.e
   

   l = n		h
   		2π

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