Chapter # 18 The Atomic Physics

PHYSICS

CHAPTER # 18 The Atomic Spectra

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The central part of atom, “nucleus” was discovered by _______ in 1911: a) Rutherford b) Joule c) Maxwell d) Henry According to electromagnetic theory, an electron moving in a circular orbit radiate _______ continuously in the form of radiations and until falls in the nucleus: a) When an electron jumps from higher energy level b) Energy c) Spectrum d) None of these When an electron jumps from higher energy level to lower energy level, it _______ energy: a) Radiates b) Absorb c) Positive d) Spectrum Bohr’s formula for the allowed frequencies of emitted radiations was correct for the experimental verification of the _______ of hydrogen atom: a) Atom b) Series c) Spectrum d) Compton The hydrogen atom spectrum was consisted of _______ sseries: a) Three b) Two c) Four d) Five First time, _______ calculated different wavelengths in the spectrum of hydrogen: a) Henry b) John Glander c) Johaun Balmer d) None of these The Balmer empirical formula is given as _______: 1 1  1 1   1  1  2  2  2 2 n  4 n n   n =R  a) =R  2 b) 1   1  2 2 n  c) =R  5 d) None of these 1 1   1  2  2  n  , “R” is known as _______ constant: In the formula n = R  2 a) Bohr’s b) Rydberg’s c) John’s d) None of these The value of “R” is _______: a) 4.119  10-4 m-1 b) 1.419  10-4 m-1 c) 1.0974  107 m-1 d) None of these The formula for “Paschen” series for hydrogen spectrum is _______ when, n = 4,5,6, _______: 1  1   1  1 1 1  2 2  2 2 n  n  a)  = R  3 b)  = R  2

A B

A C

D C A

1 n

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11. 12.

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1   1 1  2 2 n  c)  = R  4 d) None of these Neil Bohr’s model was introduced in _______: a) 1903 b) 1923 c) 1931 d) 1913 According to Bohr, the angular momentum of the electron is integral multiple of h/2  , so, we can write it as _______: nh nh mv 2  2 a) mvr = b) r =  2 c) mvr = nh d) None of these If electron moves about its own orbits then its total energy remains _______: a) Change b) Constant c) Positive d) None of these When an electron in hydrogen atom jumps from higher orbit into second orbit. The set of lines emitted is called _______: a) Balmer series b) Lyman series c) Joule series d) None of these

Bahadur Ali Qureshi

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PHYSICS

CHAPTER # 18 The Atomic Spectra

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18.

Balmer series _______ in visible region: a) Moves b) Lies c) Meet d) Radiate Lyman series lies in _______: a) Visible region b) Hydrogen atoms c) Ultraviolet region d) None of these Radius of hydrogen atom is given as _______ for n = 1,2,3, _______: a) rn = n2  0.053 nM b) rn = 0.053  n3 nM 1 c) rn = 0.53  n4 nM d) None of these The formula for nth number of orbit for hydrogen atom is _______ when n = 1,2,3, _______: 1 n 2h 2 .e2K 2 2 a) rn = 4  0 b) rn = 4 Ke m n2

19. 20. 21. 22. 23.

24.

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26. 27. 28.

C A

B

h2

2 2 2 2 c) rn = 4 Ke m d) rn =  Ke m When we put n =1, then the value of radius of first orbit is _______: a) r1 = 0.053 nM b) r1 = 5.30 nM c) r1 = 0.412 nM d) None of these When we put n =2 then the value of radius of second orbit is _______: a) 0.492 nM b) 9.123 nM c) 0.212 nM d) 2.12 nM When we put n = 9 then the value of r9 = ? a) r9 = 4.293 nM b) r9 = 0.293 nM c) r9 = 13.214 nM d) None of these We can say that the radii of the orbits are in the ratio _______: a) 1 : 4 : 19 b) 1 : 4 : 9 c) 4 : 14 : 24 d) 1 : 9 : 18 In nth orbit, the K. E. of electron is given by _______: Ke 2 Ke 3 2r n a) (K.E)n = b) (K.E)n = 2rn Ke K 2rn 2rn c) (K.E)n = d) (K.E)n = Potential energy of an electron in nth orbit is given as _______: Ke 2  Ke 2 2r n rn a) (P.E)n = b) (P.E)n = 2 Ke r c) (P.E)n = n d) None of these The total energy of an electron in nth orbit is _______ when n=1,2,3, …..:  Ke 2 Ke 2 2rn 2rn a) En = b) En = 2 e e3 r 2r c) En = n d) En = n The first ground state energy “E1” is given as _______: a) 1.43 ev b) -13.6 ev c) 4.13 ev d) 3.136 ev The value of third ground state energy “E3” is given as _______: a) -1.51 ev b) 1.51 ev c) 5.15 ev d) 1.63 ev The value of Rhydberg’s constant “RH” is _______: a) 5.134  10-7 m b) 1.0974  107 m-1 -7 c) 9.013  10 m d) 0.193  107 m-1

Bahadur Ali Qureshi

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PHYSICS

CHAPTER # 18 The Atomic Spectra

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The amount of energy required to lift an electron to atom from its lower state to higher is called: a) Excitation energy b) Photon energy c) Electron energy d) None of these The P.D. applied to move an electron from lower energy state to higher for the required excitation energy is called _______: a) Excitation energy b) Excitation Potential c) Required energy d) None of these The energy required to remove an electron from the atom is called _______: a) Ionization energy b) Potential energy c) Kinetic energy d) None of these An electronin the ground state of hydrogen atom possesses energy 13.6 ev, then the accelerating voltage required to ionize it is _______: a) 13.6 v b) 3.16 v c) 6.13 v d) 3.61 v The ionization potentials of an element are equal to the number of _______ in its atoms: a) Protons b) Electrons c) Visible radiations d) None of these X-rays travel in _______ line with the speed of light: a) Straight b) Parallel c) Equal d) None of these X-rays produce _______ in gases: a) Straight b) Parallel c) Ionization d) None of these X-rays can _______ living tissues: a) Damage b) Produce c) Ultraviolet d) None of these X-rays were discovered by _______: a) John Marrey b) Roentgen c) Maxwell d) Einstein X-rays were discovered in _______: a) 1895 b) 1985 c) 1805 d) 1920 The rest mass of x-ray photon is _______: a) One b) 1.63  104 m/s c) Zero d) Two X-rays are _______: a) Electromagnetic waves b) Positive c) Solid d) Laser Laser is a device which can produce _______: a) Gas lasers b) Solid lasers c) An intense, coherent and monochromatic beam of light d) None of these Lasers are classified as _______: a) Solids b) LIquids c) Gases d) All of these The radiation emitted from hydrogen filled discharge tube, when viewed by dispersing devices such as prism, gratings etc. shows ______: a) a line spectrum b) continuous spectrum c) linear spectrum d) all of the above When an electron jumps from higher to lower orbit: a) energy is absorbed b) energy is emitted c) neither absorbed nor emitted d) none of these When electron in hydrogen atom jumps from higher orbit into first orbit. The set of lines emitted is called: a) Balmer series b) Lyman series c) Bracket series d) Paschen series When an electron in hydrogen atom jumps from higher orbit into second orbit. The set of lines emitted is called: a) Balmer series b) Lyman series c) Bracket series d) Paschen series

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B A C A B A C A C

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PHYSICS

CHAPTER # 18 The Atomic Spectra

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When an electron in hydrogen atom jumps from higher orbit into third orbit. The set of lines emitted D is called: a) Balmer series b) Lyman series c) Bracket series d) Paschen series When an electron in hydrogen atom jumps from higher orbit into fourth orbit. The set of lines C emitted is called: a) Balmer series b) Lyman series c) Bracket series d) Paschen series Mathematically Balmer series is represented as, where R is called Rydberg’s constant: B 1 1  1 1   1  1  2  2  2 2 n n n  , n = 3,3,4 n  , n = 2,3,4 a) =R  1 b) =R  2

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1  1 1   1  1  2 2  2 2 n 3 n 4 n     , n = 5,3,4 c) =R , n = 4,3,4 d) =R Mathematically Lyman series is represented as, where R is called Rydberg’s constant: 1 1  1 1   1  1  2  2  2 2 n  n  , n = 3,3,4 n  , n = 2,3,4 n =R  2 a) =R  1 b)

A

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1  1 1   1  1  2 2  2 2 n n  , n = 4,3,4 n  , n = 5,3,4 c) =R  3 d) =R  4 Mathematically Paschen series is represented as, where R is called Rydberg’s constant: 1 1  1 1   1  1  2  2  2 2 n n n  , n = 3,3,4 n  , n = 2,3,4 a) =R  1 b) =R  2

C

1 n

1 n

1  1 1   1  1  2 2  2 2 n 3 n 4 n     , n = 5,3,4 c) =R , n = 4,3,4 d) =R Lyman series lies in: a) Visible region b) Ultraviolet region c) Infrared region d) None of the above Balmer series lies in: a) Visible region b) Ultraviolet region c) Infrared region d) None of the above Paschen series lies in: a) Visible region b) Ultraviolet region c) Infrared region d) None of the above Brackett series lies in: a) Visible region b) Ultraviolet region c) Infrared region d) None of the above Pfund series lies in: a) Visible region b) Ultraviolet region c) Infrared region d) None of the above Which of the following series in the spectrum of the hydrogen lies in the visible region of the electromagnetic spectrum? a) Paschen series b) Balmer series c) Lyman series d) Bracket series Which one of the following is NOT a fundamental postulate of Bohr’s theory of hydrogen atom? a) The toal energy of the electron in one of its allowed orbit remains constant as long as it remains in the same orbit b) An electron can not revolve in an arbitrary orbit. Only those orbits are possible for which the h 2 angular momentum of the electron about the nucleus is an integral multiple of  c) The electron can move in all possible orbits d) An atom radiates energy only when an electron jumps from an allowed orbit of higher energy E n to one of the lower energy Ep 1 n

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PHYSICS

CHAPTER # 18 The Atomic Spectra

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According to Bohr’s theory of hydrogen atom, an electron can revolve around a proton indefinitely if its path is: a) a perfect circle of any radius b) a circle of constantly decreasing radius c) a circle of an allowed radius d) an ellipse 65. In a hydrogen atom the radius of the electron orbit is governed by Bohr’s quantum rule which states that: a) the linear momentum of the electron is quantised b) the angular momentum of the electron is quantised c) the linear velocity of the electron is quantised d) the angular velocity of the electron is quantised 66. According to Bohr’s theory of hydrogen atom the angular momentum of the electron about the nucleus is an integral multiple of _______: 1 a) h b) h h h c)  d) 2 67. According to Bohr’s theory of hydrogen atom the radii r n of stationary electron is given by the equation: ke 2 ke 2 a) rn =

mv n 3 e2

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b) vn = n 2 m rn h2 he 2 2 m rn 2 m rn c) vn = n d) vn = n According to Bohr’s theory of hydrogen atom, the total energy of the hydrogen atom with its D electron revolving in the nth stationary orbit is: a) Proportional to n b) Proportional to n2 c) Inversely proportional to n d) Inversely proportional to n2 When an electron jumps from the nth (higher orbit) orbit to the pth orbit (lower orbit), the difference A of energy is given by the equation: a) hf = En - Ep b) hf = En + Ep c) hf = En d) hf = Ep - En The frequency f of electromagnetic radiation is given by the equation: C (where c is the velocity of light.) 1 a) f = c b) f =  a) vn = n

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B

2 b) rn = mv n he 2

2 2 c) rn = mv n d) rn = mv n According to Bohr’s theory of hydrogen atom the speed vn of an electron is given by the equation: ke 2 h

2 m rn

C

c  c) f = d) None of the above If the electron in the hydrogen atom jumps from an orbit whose quantum number is n to an orbit A whose quantum number is p, it emits a photon of wavelength  , given by:  1  1 1  1  1 1     n 2  p2   p2 n2    a)  = RH  b)  = RH   1 1 1  1  1  1 1     p2 n2  p n R  c)  = RH  d)  = H  The transitions of inner-shell electrons in heavy atoms give rise to _______: D   a) -rays b) -rays c)  -rays d) x-rays

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PHYSICS

CHAPTER # 18 The Atomic Spectra

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X-rays are a part of electromagnetic spectrum and are characterized by frequencies higher than those of: a) visible radiations b) infrared radiations c) ultraviolet radiations d) none of the above X-rays are: a) positively charged particles b) negatively charged particles c) neutral particles d) none of these The study of the spectrum of characteristic x-rays helps us to: a) measure the energy of the incident electrons b) measure the wavelength of the incident electrons c) measure the energy of the emitted x-rays d) identify the element of which the target is made The maximum frequency limit of the continuous x-rays spectrum depends upon _______: a) the atomic number of the atoms of the target b) the kinetic energy of the incident electrons c) the maximum frequency limit of the characteristic x-rays spectrum d) the degree of vacuum in the x-ray tube The device that produces an intense, monochromatic and coherent beam of light based on ----emission of photons from atoms, is called: a) laser b) x-rays c) discharge tube d) cyclotron An interesting application of laser is the production of three dimensional images called: a) polygons b) holgrams c) ovals d) none of these The laser device used to fragment gallstones and kidney stones is called: a) laser beam b) laser scanner c) laser lithotropter d) ruby laser The wavelength of x-rays is of the order of: a) 10-12 m b) 10-10 m -8 c) 10 m d) 10-6 m When fast moving electrons strike a metal target inside a partially evacuated tube: a) cathode rays are produced b) cosmic rays are produced c) x-rays are produced d) alpha rays are produced Production of x-rays is a reverse phenomenon of: a) Photoelectric effect b) Compton effect c) Pair production d) Annihilation of matter Choose the wrong statement out of the following: a) x-rays are not refracted as they pass from one medium to another b) like visible light, x-rays are diffracted at an obstacle c) x-rays can cause ionization of the atoms of a liquid d) x-rays are deflected by electric and magnetic fields In an x-ray electrons are accelerated by applying a high voltage V. If e is the electronic charge and h the Planck’s constant, the highest frequency Vmax of the emitted x-rays is given by: 1 e2V2 eV 2 a) Vmax = h b) Vmax = 2 h

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eh e2h 2 2 c) Vmax = 2 V d) Vmax = V X-rays were discovered by: B a) Madam Curie b) Roentgen c) Coolidge d) Laue X-rays are produced when an element of high atomic weight is bombarded by high energy: B a) Protons b) Electrons c) Neutrons d) Photons Which one of the following parameters of the emitted x-rays increases when the potential difference B between the electrodes of an x-ray tube is increased? a) Intensity b) Frequency c) Wavelength d) Speed

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