2nd Year Physics Chapter 20 Atomic Spectra Notes MCQs Solutions

physics 12th notes mcqs chapter 20

1. Kß x-ray is emitted when an electron from:


2. Energy required by an atom to move from ground state to higher
energy state is called


3. In electronic transition, atom cannot emit:


4. After the emission of X-ray, the atom of the target is


5. The radius of 3rd Bohr orbit in hydrogen atom is greater than the radius of  orbit by a factor of


6. The numerical value of ground state energy fot the hydrogen atom


7. In the general formula for spectral series, if we put P = 3, we get the formula for:


8. Which series is visible from the following:


9. Paschen series lies in the


10. Bohr was presented atomic model of hydrogen in:


11. An example of an absorption spectrum is the spectrum of:   


12. The branch of Physics in which laser is studied:


13. In Bohr’s atomic model, the lowest orbit corresponds to:


14. The minimum wavelength of x-rays can further be reduced by:


15. The velocity of laser light is:        


16. Radiation with wavelength longer than red light is called


17. X-ray tube used for production of X-rays contains:


18. The radii of different orbits around the nucleus of an atom is given by:


19. The process of formation of spectrum is known as:    


20. X-rays are:              


21. Life time of metastable states is: 


22. For production of X-rays, the target must be of:


23. The maximum frequency in the spectrum from x-rays tube is directly proportional to the:


24. Balmer series lies in


25. For holography we use a beam of:


26. Bohr’s atomic model of hydrogen was proposed by Niel Bohr in


27. Laser is beam of light which is:


28. The photons emitted in inner shell transition are called:


29. In 1913, modern tube for production of X-rays was designed by


30. For the production of x-rays, the target metal should be bombarded by:


31. By CAT scans, we can detect the density difference of the order of:


32. X-rays exhibit the phenomenon of


33. The magnitude of Rydberg constant is


34. An electron of the hydrogen atom in the second orbit, is called its:


35. The Balmer series is obtained when all the transitions of electron
terminate on


36. The radius of 10th orbit in hydrogen atom is:


37. X-rays can be used to:                  


38. X-ray photons can not produce pair production because


39. X-rays are


40. Radiation, with wavelength shorter than violet is called:


41. Most commonly used type of gas laser is:                       


42. Helium-Neon laser discharge tube contains neon:


43. Total energy of an electron in an orbit around the nucleus is the sum of


44. Operation of a laser depends upon:       


45. In He-Ne laser, the laser action is produced by:


46. If the ionization energy of hydrogen atom is 13.6 eV, its ionization potential will be:


47. When an electron jumps from a higher orbit of energy En to a lower orbit of energy Ep, the frequency f of the emitted radiation is given by
the relation


48. The radiations emitted from hydrogen filed discharge tube can be analyzed into:


49. The experimental value of Rydberg’s constant is:


50. In hydrogen spectrum, which one the following series lies in the ultraviolet region:


51. Laser is a device which can produce


52. Townes and Authers Schowlan is:


53. Hydrogen atom spectrum does not lie in


54. The longest wavelength of light which ionizes a hydrogen atom is:


55. The penetrating power of x-rays increases with


56. In an electronic transition, an atom cannot emit


57. Laser light is


58. The value of Rydberg’s constant is


59. The I Bohr atom in the hydrogen atom has radius:


60. Tick the series lies infrared region:                    


61. In the production of laser beam for each incident photon, we will have two photons going:


62. The first series, which was identified in the spectrum of hydrogen is called:


63. The radius of the third Bohr orbit in hydrogen atom is greater than the
radius of the first orbit by a factor of


64. In which region of electromagnetic spectrum of Hydrogen, the balmer series lies ?


65. The value of Rydberg constant is:


66. Balmer series was identified in:


67. Different types of lasers are:


68. The potential required to remove an electron from the atom is called


69. Characteristic x-rays are produced from:


70. The residing time of atoms in meta stable state in case of laser action


71. The velocity of x-rays is equal to that of:                       


72. Atomic spectra are


73. First spectral series of Hydrogen atoms was discovered by


74. X-rays are similar in nature to


75. When x-rays are passed through aluminium sheets, what happens to their thickness:


76. The energy in electron volt necessary to remove the most loosely
bound electron from the neutral atom is known as


77. The process by which lesser beam can be used to generate 3- dimensional images of objects is called:


78. Spectrum shows the number of component colour present in certain light in terms of:


79. What is the color of light emitted from He-Ne Laser?


80. The results of spectra obtained by Balmer were expressed in 1896 by:


81. X-rays are:


82. The line spectrum of hydrogen atom contains the spectral lines in the
region of


83. The radius of first Bohr orbit in the hydrogen atom is


84. mvr is the expression for:


85. X-rays are affected by


86. Tick the series lies in visible region:                   


87. Which of the following is one of the spectral series of atomic hydrogen:


88. For Panchen series the value of n starts from


89. When an electron exist in its lowest state it is called:


90. Energy of hydrogen atom in the ground state is


91. The electric potential energy of an electron in an orbit at a distance rn
from the positive charge


92. X-ray photons cannot produce pair production because:


93. For the stability of nuclear model, Rutherford proposed:


94. X-rays are radiation of


95. En-Ep=hf is the energy of


96. Paschen series is obtained when all the transitions of electron
terminate on


97. Kα- X rays are produced due to transition of electrons from:


98. The scientist who studies the spectrum of hydrogen in visible light, wavelength range was:


99. Quality of X-rays depends upon


100. The characteristic x-rays appear as:


101. The value of radius of 1st Bohr’s orbit is


102. The energy of electron in ground State of hydrogen atom is -13.6ev, then its energy in forth orbit


103. Balmer series is obtained when all the transitions of electron terminate on:


104. How many postulates are upon which the Bohr’s theory of hydrogen
atom is based


105. The transition’s of electrons in the hydrogen atom result in the emission of spectral lines in the:


106. The reverse phenomenon of photoelectric effect is called as:


107. The penetrating power of x-rays depends upon their:


108. According to Rutherford nuclear model, the major constituents of the nucleus are:


109. When X-rays are passed through successive aluminum sheets, their hardness


110. Which is not true for x-rays


111. If the radius of first orbit of hydrogen atom is 0.53A⁰ , the radius of
second orbit will be


112. Which of the following series lies in the ultraviolet region?


113. The simplest spectrum is that of


114. The reverse process of photo-electric effect is called:


115. In the state n=∞ of hydrogen atom, total energy of electron is


116. The following gas was identified in the sun using spectroscopy:


117. Bohr’s postulates explained by:              


118. If the radius of first orbit of hydrogen atom is 0.053nm , the radius of
second orbit will be


119. The characteristic x-rays spectrum is due to:


120. The idea of laser was introduced by:      


121. The first theory about the structure of an atom was introduced by. 


122. The radius of 1 st Bohr’s orbit for hydrogen is:


123. The energy of the 4th orbit in hydrogen atom is


124. The excited atoms return to their ground state in


125. The spectral series that contains transitions terminating on the ground level of hydrogen is called:


126. Atom can reside in metastable state for


127. According to Bohr, the angular momentum of an electron in the
allowed orbit is given by


128. Study of hydrogen visible spectrum in:


129. The x-rays diffraction with crystal was first studied by:


130. Brackett series lies in the


131. The energy of the electron in the first allowed orbit of hydrogen atom


132. The dimensions of Planck’s constant is same as that of


133. Quality of x-rays depends upon:             


134. The diameter of an atom is of the order of:


135. If an electron jumps from lower to higher orbit it will


136. Wavelength shorter than violet is called


137. X-rays can be:


138. Electromagnetic rays which lies above the x-rays region are called:


139. X-rays were discovered by


140. During the transition of electron of hydrogen atom from higher orbit to a third orbit, a photon of:


141. Laser can be made by creating:  


142. Which of the following series of H-Spectrum lies in ultraviolet region:


143. X-rays are diffracted by crystal but not by a diffraction grating because:


144. K-series of characteristic x-rays spectrum results when all the transitions of inner-shell electrons terminate an:


145. In Bohr atomic model, the electron does not fall into the nucleus because:


146. In hydrogen atom, which one of the following series lies in the infrared region:


147. Speed of the electron in the first Bohr’s orbit is:


148. Life time of excited state is


149. The penetrating power of x-rays is comparable with that of:


150. Most efficient tube for production of x-rays was designed by:


151. Rutherford’s nuclear model predicted:              


152. When electron absorbs energy, it jumps to


153. In Helium-Neon laser, discharge tube is filled with Neon gas:


154. Which series lies in the ultraviolet region?


155. The SI unit of Rydberg constant is:        


156. The value of Planck’s constant is:


157. Braking radiation causes:


158. Laser beam can be used to generate three dimensional images of object in a process called:


159. Which is not characteristic of LASER?


160. X-rays are


161. If electrons jumps from second orbit to first orbit in hydrogen atom it emits photon of:


162. Radius of 3rd Bohr orbit in hydrogen atom is greater than radius of 1 orbit by


163. The rest mass of x-ray photon is


164. Rutherford concluded that central part of an atom is:


165. Real mass of an electron is


166. Net force on an electron in an orbit around the nucleus will be:


167. The numerical value of ground state energy of an electron in an orbit is the measure of:


168. The Bracket series is obtained when all the transitions of electron
terminate on


169. Reflecting mirrors in laser is used to:    


170. The unit of RH (Rydberg’s constant) is:


171. The first spectra line of K-series of characteristics x-rays spectrum results when:


172. What is speed of electron in the first Bohr orbit?


173. The transitions of inner shell electrons in heavy atoms give rise to the emission of:


174. Brackett series is obtained when electronic transitions terminate on the:


175. The uncertainty in its energy will be:


176. Balmer series lies in that region of electromagnetic wave spectrum, which is known as:


177. Laser is device which can produce:       


178. In a electronic transition atom cannot emit:


179. Atomic spectra are the examples of spectra.


Short Questions

1. Balmer series of hydrogen tom is photographed in the form of a number of lines whose wave length increase from left to right or extreme left line will be the brightest?
2. Bohr’s theory of hydrogen atom is based upon several assumptions. Do any of these assumptions contradict classical physics ?
3. Can an electron reside inside the atom ?
4. Can the electron in the ground state of hydrogen photon of energy 13.6 eV or greater than 13.6 eV?
5. Can x- rays be reflected, refracted, diffracted and polarized just like any other waves? Explain.
6. Compute the shorter wavelength radiation in the Balmer series?
7. Define excitation energy?
8. Define ionization energy?
9. Describe the atomic processes in the target of an X – rays tube whereby X – rays line spectra are produced?
10. Explain the terms:- (A). Excitation Potential (B). Ionization potential
11. Explain the working of a Cat – scanner?
12. Explain what is difference between laser light and light from incandescent light?
13. Explain why a glowing gas gives only certain wavelength of light and why that is capable of absorbing the same wavelength? Give a reason why it is transparent to other wavelengths?
14. Explain why laser action could not accur without population inversion between atomic levels?
15. Find the speed of an electron in the first Bohr orbit ?
16. How can the hydrogen spectrum contain so many lines although hydrogen contains one electron only?
17. How does a meta stable state differ from a normal excited state of an atom?
18. How many electronic orbits are there in a hydrogen atom ?
19. Hydrogen gas at atom – temperature absorbs tight of wavelengths equal to the lines in the Lyman series but not those of the Blamer series? Explain.
20. In what region does Balmer series lie?
21. In what region does Braket series lie?
22. In what region does Lyman series lie ?
23. In what region does Paschen series lie?
24. In what region does Pfund series lie ?
25. Is energy conserved when an atom emits a photon of light?
26. List the colour of line spectra of an excited hydrogen atom?
27. Name the types of lasers ?
28. Name the types of spectra ?
29. What is the value of Plank’s constant ?
30. When an atom is said to be ionized ?
31. State the three postulates of Bohr’s theory of atomic structure?
32. The electromagnetic wave energy emitted in space by a point source obeys inverse square law ?
33. The electron in a hydrogen atom requires an energy of 10.2 eV for excitation to a higher energy level . A photon and an electron each of energy 10.5 eV are incident upon the atom which of these can excite the atom? Give explanation in support of your answer?
34. The hydrogen atom contains only a single electron and yet the hydrogen spectrum contains may lines?
35. The orbital electron of a hydrogen atom moves with a speed of 5.456 x 10⁵ ms¹ find the value of quantum number ‘n’ associated with this electron ?
36. V. If these electrons were slowed down in a target. What will be the minimum wavelength of x-rays produced ?
37. What are characteristic X-rays ?
38. What are different kinds of lasers?
39. What are infra-red radiations ?
40. What are main characteristics of a line spectrum? Explain how line spectra can be used for the identification of elements?
41. What are the advantages of laser over ordinary light?
42. What are X –rays?
43. What do you mean by a stationary orbit as postulated by Bohr ?
44. What do you mean by helium-neon laser ?
45. What do you understand by excitation energy and ionization energy?
46. What does the name Laser stand for. Define it?
47. What is a CAT scanner?
48. What is atomic spectrum ?
49. What is band spectrum ?
50. What is continuous spectrum ?
51. What is difference between the terms normal population and population inversion ?
52. What is excited state ?
53. What is ground state ?
54. What is inner shell transition of electron?
55. What is laser principle?
56. What is Laser?
57. What is line spectrum ?
58. What is meant by a line spectrum? Explain, how line spectrum can be used for the identification of elements?
59. What is metastable state?
60. What is spectroscopy?
61. What is spectrum ?
62. What is spontaneous Emission?
63. What is stimulated emission ?
64. What is the energy of electron of hydrogen atom in the first orbit (ground state)?
65. What is the net force on an electron in an orbit revolving around the nucleus ?
66. What is the ordinary life time of an electron in the excited state ?
67. What is the total energy of an electron of hydrogen atom?
68. What is the value of ionization energy of hydrogen atom?
69. What is the value of radius of first Bohr orbit?
70. What is the value of Rydberg’s constant ?
71. What is the wave length range of x-rays ?
72. What is the word ‘laser’ stands for ?
73. What is uncertainty with the atom regarding to position of electrons ?
74. When an atom is said to be excited ?
75. When did Neil Bohr propose a model of hydrogen atom ?
76. When did Rontgen discover x-rays ?
77. Whether black body radiation spectrum is a continuous spectra ?
78. Whether molecular spectra are the example of band spectra ?
79. Which laser is mist commonly used ?
80. Why do you mean when say that the atom is excited?
81. Why does laser usually emit only one particular color of light rather than several colors?
82. Why does solids give rise to a continuous spectrum while hot gases gives rise to line spectrum?
83. Why does the frequencies of characteristic X – rays depend upon the type of material used for the target?
84. Write any four properties of x-rays ?
85. Write any four uses of x-rays ?
86. Write down some applications of laser?
87. Write some important uses of laser?

Long Questions

1. Explain atomic spectrum / spectra?
2. Write Bohr’s second postulate and find out formula for Bohr quantized radii.
3. Define spectroscopy. Derive expression for radii of quantized orbit.
4. What is hydrogen emission spectrum?
5. What are X-rays? How are they produced?
6. What is CAT-Scanner?
7. What is the biological effects of X-rays?
8. Explain characteristics X-rays and continuous X-ray spectra. Also write two uses of X-rays.
9. Explain the uncertainty within the atom.
10. What does the word laser stand for? Write any four uses of laser.
11. A hydrogen atom is in its ground state (n = 1). Using Bohr’s theory, calculate (a) the radius of the orbit, (b) the linear momentum of the electron, (c) the angular momentum of the electron, (d) the kinetic energy, (e) the potential energy, and (f) the total energy.
12. What are the energies in eV of quanta of wavelength 400, 500 and 700 nm?
13. An electron jumps from a level Ei = -3.5 x 10⁻¹⁹J to Ef = -2 x 10⁻¹⁸J. What is the wavelength of the emitted light?
14. Find the wavelength of the spectral line corresponding to the transition in hydrogen from n = 6 state to n = 3 state.
15. Compute the shortest wavelength radiation in the Balmer series? What value of n must be used?
16. Calculate the longest wavelength of radiation for the Paschen series.
17. Electron in an x-ray tube are accelerated through a potential difference of 3000V. If these electrons were slowed down in a target, what will be the minimum wavelength of x-ray produce?
18. The wavelength of K-x-ray from copper is 377 x 10⁻¹⁰ m. What is the energy difference between the two levels from which this transition results?
19. A tungsten target is struck by electrons that have been accelerated from rest through 40KV potential difference. Find the shortest wavelength of the bremsstrahlung radiation emitted?
20. The orbital electron of a hydrogen atom moves with a speed of 5.456 x 10⁵ ms⁻¹, (a) find the value of the quantum number ‘n’ associated with this electron, (b) calculate the radius of this orbit, and (c) the energy of the electron in this orbit?

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