JEE Physics Atoms MCQs Set A

Question: An alpha particle colliding with one of the electrons in a gold atom loses

• a) Little of its energy
• b) Most of its momentum
• c) Most of its energy
• d)

  

Answer: Little of its energy

Question: According to classical theory, Rutherford atom was

• a) Electrostatically stable
• b) Electrodynamically unstable
• c) Semi stable
• d) Stable

Answer: Electrostatically stable

Question: The angular momentum of an electron in a hydrogen atom is proportional to (where r is radius of orbit)

• a)

  

• b)

  

• c)

  

• d) none of these

Answer:

Question: When a hydrogen atom is raised from the ground state to third state

• a) Potential energy increases and kinetic energy decreases
• b) Both kinetic energy and potential energy decrease
• c) Both kinetic energy and potential energy increase
• d) Potential energy decreases and kinetic energy increases

Answer: Potential energy increases and kinetic energy decreases

Question:  What is the angular momentum of an electron in Bohr’s hydrogen atom whose energy is –3.4 eV?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The ground state energy of H - atom is –13.6 eV. The energy needed to ionise H - atom from its second excited state is

• a) 1.51 eV
• b) 3.4 eV
• c) 13.6 eV
• d) 12.1 eV

Answer: 1.51 eV

Question: If element with principal quantum number n > 4 were not allowed in nature, then the number of possible elements would be

• a) 60
• b) 32
• c) 4
• d) 64

Answer: 60

Question: The angular speed of electron in the nth orbit of hydrogen atom is

• a)

  

• b)

  

• c) Inversely proportional to n
• d) None of these

Answer:

Question: Of the various series of the hydrogen spectrum, the one which lies completely in the ultraviolet region is

• a) Lyman series
• b) Balmer series
• c) Paschen series
• d) Brackett series

Answer: Lyman series

More Questions..............................

Question: As the n (number of orbit) increases, the difference of energy between the consecutive energy levels

• a) Decreases
• b) Remains the same
• c) Increases
• d) Sometimes increases and sometimes decreases

Answer: Decreases

Question: The magnetic field induction produced at the centre of orbit due to an electron revolving in n^th orbit of hydrogen atom is proportional to

• a) n^–5
• b) n^–3
• c) n⁵
• d) n³

Answer: n^–5

Question: The speed of an electron in the orbit of hydrogen atom in the ground state is

• a) c/137
• b) c/2
• c) c/10
• d) c

Answer: c/137

Question: If the radius of the first orbit of hydrogen atom is 5.29 × 10^–11 m, the radius of the second orbit will be

• a) 21.16 × 10^–11 metre
• b) 15.87 × 10^–11 metre
• c) 10.58 × 10^–11 metre
• d) 2.64 × 10^–11 metre

Answer: 21.16 × 10^–11 metre

Question: The ratio of minimum to maximum wavelength of radiation emitted by transition of an electron to ground state of Bohr’s hydrogen atom is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: In Bohr’s model of the hydrogen atom, the ratio between the period of revolution of an electron in the orbit of n = 1 to the period of revolution of the electron in the orbit n = 2 is

• a) 1 : 8
• b) 1 : 4
• c) 2 : 1
• d) 1 : 2

Answer: 1 : 8

Question: How many times does the electron go round the first Bohr orbit in a second?

• a) 6.57 × 10¹⁵
• b) 6.57 × 10¹³
• c) 6.57 × 10¹⁰
• d) 6.57 × 10⁵

Answer: 6.57 × 10¹⁵

Question: The ratio of the energies of the hydrogen atom in its first excited state to second excited state is

• a) 9/4
• b) 4
• c) 4/9
• d) 1/4

Answer: 9/4

Question: Which of the following transitions in a hydrogen atom emit photons of lowest frequency?

• a) n = 4 to n = 3
• b) n = 3 to n = 1
• c) n = 4 to n = 2
• d) n = 2 to n = 1

Answer: n = 4 to n = 3

Question: The energy of hydrogen-atom in its ground state is –13.6 eV. The energy of the level corresponding to n = 5 is

• a) –0.544 eV
• b) –5.40 eV
• c) –0.85 eV
• d) –2.72 eV

Answer: –0.544 eV

Question: If the electron in hydrogen atom jumps from third orbit to second orbit, the wavelength of the emitted radiation is given by

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The total energy of an electron in the hydrogen atom in the ground state is –13.6 eV. The kinetic energy of this electron is

• a) 13.6 eV
• b) 0
• c) –13.6 eV
• d) 6.8 eV

Answer: 13.6 eV

Question: Using Bohr’s formula for energy quantization, the ionisation potential of the ground state of Li⁺⁺ atoms is

• a) 122 V
• b) 13.6 V
• c) 3.4 V
• d) 10.2 V

Answer: 122 V

Question: Which series of hydrogen atom lie in infra red region?

• a) Brackett, Paschen and Pfund
• b) Lyman
• c) Balmer
• d) All of these

Answer: Brackett, Paschen and Pfund

Question: When an electron is excited to n^th energy state in hydrogen, the possible number of spectral lines emitted are

• a)

  

• b)

  

• c) 2n
• d) n

Answer:

Question: Which state of triply ionised beryllium (Be3⁺) has the same orbital radius as that of the ground state of hydrogen?

• a) 2
• b) 3
• c) 4
• d) 1

Answer:  2

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) a < b, b > c
• b) a > b, b > c
• c) a > b, b < c
• d) a < b, b < c

Answer: a < b, b > c

Question: X-rays incident on a material

• a) All of these
• b) Will transfer energy to it
• c) Will exert a force on it
• d) May cause emission of electrons

Answer: All of these

Question: A situation of population inversion is related to

• a) LASER
• b) Matter wave
• c)

  

• d)

  

Answer: LASER

Question: In He-Ne laser, metastable state exists in

• a) Ne
• b) He
• c) Neither He nor Ne
• d) Both

Answer: Ne

Question: If the emitted radiation falls in the microwave region, the device is termed as

• a) MASER
• b) LASER
• c) Both
• d) None of these

Answer: MASER

Question: Laser is/are

• a) All of these
• b) Highly monochromatic
• c) Highly coherent
• d) Highly directional

Answer: All of these

Question: If the potential difference V applied to the coolidge tube is doubled, then the cut off wavelength

• a) Is halved
• b) Is quadrupled
• c) Is doubled
• d) Remains unchanged

Answer: Is halved

Question: Penetrating power of X-rays increases with increase in

• a) Accelerating potential
• b) Mass number of the target material
• c) Wavelength
• d) Filament current

Answer: Accelerating potential

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: An X-ray tube has a short wavelength end at 0.45Å. The voltage of tube is

• a) 27500 V
• b) 60600 V
• c) 9600 V
• d) 450000 V

Answer: 27500 V

Question: X-rays of a particular wavelength are used to irradiate sodium and copper surfaces in two separate experiments and stopping potentials are determined. The stopping potentials are

• a) Greater for sodium
• b) Greater for copper
• c) Infinite in both cases
• d) Equal in both cases

Answer: Greater for sodium

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: When a hydrogen atom emits a photon of energy 12.09 eV, its orbital angular momentum changes by (where h is Planck’s constant)

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A hydrogen atom is in ground state. In order to get six lines in its emission spectrum, wavelength of incident radiation should be

• a) 970 Å
• b) 1025 Å
• c) 825 Å
• d) 800 Å

Answer: 970 Å

Question: The X-ray beam coming from the X-rays tube will be

• a) Having all wavelengths greater than a certain minimum wavelength
• b) Dichromatic
• c) Monochromatic
• d) Having all wavelengths between a minimum and maximum wavelengths

Answer: Having all wavelengths greater than a certain minimum wavelength

Question: If the energy in the first excited state in hydrogen atom is 23.8 eV then the potential energy of a hydrogen atom in the ground state can be assumed to be

• a) Zero
• b) – 13.6 eV
• c) 23.3 eV
• d) 10 eV

Answer: Zero

Question:

• a) 83.9 eV
• b) 29.5 eV
• c) 24.9 eV
• d) 54.4 eV

Answer: 83.9 eV

Question: The maximum wavelength that a sample of hydrogen atoms can absorb is

• a) 1216 Å
• b) 912 Å
• c) Infinite
• d) 1028 Å

Answer: 1216 Å

Question: The lines in Balmer series have their wavelengths lying between

• a) 3647 Å to 6563 Å
• b) Zero to infinity
• c) 642 Å to 3000 Å
• d) 1266 Å to 3647 Å

Answer: 3647 Å to 6563 Å

Question: If an electron in hydrogen atom jumps from third orbit to second orbit, the frequency of the emitted radiation is given by (c is speed of light)

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question: Identify the incorrect relationship

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 4
• b) 3
• c) 2
• d) 1

Answer: 4

Question: If radius of first orbit of hydrogen atom is 5.29 × 10^–11 m, the radius of fourth orbit will be

• a) 8.46 Å
• b) 10.23 Å
• c) 9.22 Å
• d) 9.48 Å

Answer: 8.46 Å

Question: Ratio of magnetic dipole moment to the angular momentum for hydrogen like atoms is (e and m are electronic charge and mass respectively)

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The ratio of energies of hydrogen atom in its first excited state to third excited state is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: What should be the ratio of minimum to maximum wavelength of radiation emitted by transition of an electron to ground state of Bohr’s hydrogen atom?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The product of angular speed and tangential speed of electron in n^th orbit of hydrogen atom is

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question: Ground state energy of H-atom is –13.6 eV. The energy needed to ionise H-atom from its second excited state is

• a) 1.51 eV
• b) 3.4 eV
• c) 13.6 eV
• d) 12.1 eV

Answer: 1.51 eV