Thursday, May 4, 2023

H C Verma solutions, X-rays, Chapter-44, OBJECTIVE-II, Concepts of Physics, Part-II

X - rays


OBJECTIVE-II

      1.  For harder X-rays, 
(a) the wavelength is higher
(b) the intensity is higher
(c) the frequency is higher
(d) the photon energy is higher.  

Answer: (c), (d).    


Explanation:  Harder X-rays mean that X-rays have a comparatively more penetrating power. The more the energy of photons more penetrating power. For higher energy of photons, frequency is also higher. Hence options (c) and (d) are correct. 
  With higher wavelengths, the energy of photons decreases. So option (a) is not correct.  
   The increase in intensity does not increase the energy of a photon. Hence option (b) is also incorrect.






      2. The cutoff wavelength of X-rays coming from a Coolidge tube depends on the 
(a) target material 
(b) accelerating voltage
(c) the separation between the target and the filament
(d) the temperature of the filament.   

Answer: (b).    


Explanation: The cutoff wavelength of X-rays is given as 
      λₘₐₓ = hc/eV
Here hc/e is constant. Hence the cutoff wavelength of X-rays depends only on the accelerating voltage V. Only (b) is the correct option.





      3.  Mark the correct options.
(a) an atom with a vacancy has smaller energy than a neutral atom.
(b) K X-ray is emitted when a hole makes a jump from the K shell to some other shell. 
(c) The wavelength of K X-ray is smaller than the wavelength of L X-ray of the same material.
(d) The wavelength of Kₐ X-ray is smaller than the wavelength of Kᵦ X-ray of the same material.  

Answer: (b), (c).    


Explanation:  When the parts of atoms are far away we assume their energy is zero. When they are brought together the energy of the atom decreases and expresses as negative. Hence an atom with a vacancy has higher energy than a neutral atom. Option (a) is incorrect.
       K X-rays are produced when an electron from another shell jumps to the K shell. Thus the vacancy or hole in the K shell goes to that shell from where the electron has jumped. In other words, the hole has jumped from the K shell to some other shell. Option (b) is correct. 
     K X-ray has an energy equal to the difference between the K and L shells while L X-ray has an energy equal to the difference between L and M shells. In the same material, the former energy is higher than the latter. Hence option (c) is correct.   
       Kₐ X-rays are produced when an electron transition takes place from L shell to K shell while Kᵦ X-rays are the result of an electron transition from M shell to K shell. So in the same material, Kₐ X-rays will have lower energy than the Kᵦ X-rays. So Kᵦ X-rays will have a smaller wavelength than the Kₐ X-rays.  Option (d) is incorrect.

 





      4.  For a given material, the energy and wavelength of characteristic X-rays satisfy,
(a) E(Kₐ) > E(Kᵦ) > E(Kᵧ)
(b) E(Mₐ) > E(Lₐ) > E(Kₐ)
(c) λ(Kₐ) > λ(Kᵦ) > λ(Kᵧ)
(d) λ(Mₐ) > λ(Lₐ) > λ(Kₐ) 
    

Answer: (c), (d).    


Explanation:  Option (a) is in reverse order, hence incorrect. 
     As we go higher in shells the energy difference between consecutive shells decreases. Hence the energy given in option (b) is in reverse order, thus incorrect.
         For the same material, the energy of Kₐ X-ray is less than the energy of Kᵦ X-ray and it is further less than the energy of Kᵧ X-ray. Hence the wavelength of Kₐ X-ray is greater than the wavelength of Kᵦ X-ray. Also, the wavelength of the Kᵦ X-ray is greater than the Kᵧ X-ray. Hence option (c) is correct.
      For the reason explained in the second paragraph above, the wavelength of Mₐ X-ray is greater than the wavelength of Lₐ X-ray, and the wavelength of Lₐ X-ray is greater than the wavelength of Kₐ X-rays. Hence option (d) is correct.  

  





      5.  The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation,
(a) the intensity increases 
(b) the minimum wavelength increases
(c) the intensity remains unchanged
(d) the minimum wavelength decreases. 

Answer: (c), (d).    


Explanation:  With the increase in the potential difference in the Coolidge tube, the number of striking electrons and hence the emitted photons do not change. Hence the intensity remains unchanged. However, due to increased potential difference, the energy of the striking electrons increases and the cutoff wavelength of emitted X-rays decreases. So options (c) and (d) are correct, not options (a) and (b).  





      6.  When an electron strikes the target in a Coolidge tube, its entire kinetic energy
(a) is converted into a photon
(b) may be converted into a photon
(c) is converted into heat
(d) may be converted into heat. 

Answer: (b), (d).    


Explanation: When the striking electrons enter the target, they go into many collisions before being stopped. However, all the electrons do not have the same number of collisions and not all in similar ways. A part or whole of the kinetic energy of a colliding electron may increase the vibration of the molecules of the target (Which increases the temperature of the target) and the rest may be converted into photons of X-rays. Hence options (b) and (d) are correct.  

    





      7.  X-ray incident on a material 
(a) exerts a force on it
(b) transfers energy to it
(c) transfers momentum to it
(d) transfers impulse to it.  

Answer: All.    


Explanation:  X-rays are electromagnetic radiation, hence their photons have energy as well as momentum. When X-rays are incident on a material a part or whole of it may be absorbed depending on the nature and thickness of the material. This absorbed part of X-rays transfers their momentum and impulse to the material. Due to this, they exert force on the material. The absorbed X-rays lose their energy to the material that appears as heat. Hence all the options are correct. 


      





      8.  Consider a photon of continuous X-ray and a photon of characteristic X-ray of the same wavelength. Which of the following is/are different for the two photons? 
(a) frequency
(b) energy
(c) penetrating power
(d) method of creation.  

Answer: (d).    


Explanation:  X-rays having the same wavelength have the same frequency, the same energy, and hence the same penetrating power. There will be no difference in the property. 
  Continuous X-ray is produced due to the loss of kinetic energy of the striking electron while the characteristic X-ray is produced when the striking electron dislodges an inner orbit electron of the atom of the material and this vacancy is filled by any outer orbit electron, thus releasing the photon. So the only difference between both of them is the method of creation. Only option (d) is correct. 

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Links to the Chapters





CHAPTER- 34- Magnetic Field

CHAPTER- 29- Electric Field and Potential











CHAPTER- 28- Heat Transfer

OBJECTIVE -I







EXERCISES - Q51 to Q55


CHAPTER- 27-Specific Heat Capacities of Gases

CHAPTER- 26-Laws of Thermodynamics


CHAPTER- 25-CALORIMETRY

Questions for Short Answer

OBJECTIVE-I

OBJECTIVE-II


EXERCISES - Q-11 to Q-18


CHAPTER- 24-Kinetic Theory of Gases







CHAPTER- 23 - Heat and Temperature






CHAPTER- 17 - Light Waves




CHAPTER- 14 - Fluid Mechanics




CHAPTER- 13 - Fluid Mechanics


CHAPTER- 12 - Simple Harmonic Motion









CHAPTER- 11 - Gravitation





CHAPTER- 10 - Rotational Mechanics






CHAPTER- 9 - Center of Mass, Linear Momentum, Collision


CHAPTER- 8 - Work and Energy

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CHAPTER- 7 - Circular Motion

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CHAPTER- 6 - Friction

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For more practice on problems on friction solve these- "New Questions on Friction".

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CHAPTER- 5 - Newton's Laws of Motion


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Click here for→Newton's Laws of Motion,Exercises(Q.No. 13 to 27)

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CHAPTER- 4 - The Forces

The Forces-

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CHAPTER- 3 - Kinematics - Rest and Motion

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CHAPTER- 2 - "Physics and Mathematics"

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