Case Study Questions Class 12 Physics Chapter 12 Atoms
CBSE Class 12 Case Study Questions Physics Atoms. Term 2 Important Case Study Questions for Class 12 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Atoms.
At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.
CBSE Case Study Questions Class 12 Physics Atoms
Case study 1:
Each element is having specific properties as it emits or shows the specific emission spectrum of radiation. The emission line spectrum has bright lines on the dark surface. The hydrogen spectrum consist of series namely Balmer, Lyman, Paschen, Brackett and Pfund series. The Lyman series is formed in the ultraviolet region while Paschen, Brackett and Pfund series are in the infrared region. According to Bohr’s first postulate, electrons are revolving in particular stable orbits without radiating any form of energy. And in his second postulate he told that, these electrons are revolving around the nucleus in stable orbits which are having angular momentum equal to integral multiple of h/2π. And third postulate tells us that, when electron jumps from higher energy state to lower energy state it will emits some amount of energy and which is equal to the energy difference between those energy levels.
And he gave the energy of an electron in an hydrogen atom as
En = -13.6/ n2 eV
The negative sign shows that electron is tightly bound with the nucleus. And when n = 1, then corresponding energy of electron is called as ground state energy. Bohr’s model is only applicable to single electron system like hydrogen and it cannot be applicable to helium atom also which is having two electrons.
Questions:
Q 1.) In hydrogen atom, the ground state energy is given by___
a) +13.6 eV
b) -13.6 J
c) -13.6 KJ
d) -13.6 eV
Q 2.) According to Bohr’s second postulate, the angular momentum L is given by
a) L= h/2π
b) L = nh/2π
c) L = 2π/h
d) L = 2π/ nh
Q 3.) What is the shortest wavelength in the Balmer series
a) 656.3 nm
b) 364.6 nm
c) 656.3 mm
d) 364.6 mm
Q 4.) What are the Ha, HB and Hv lines in the emission spectrum of hydrogen atom?
Q 5.) Give the Balmer’s formula?
Answer key:
Q 1.) d) -13.6 eV
Q 2.) b) L = nh/2π
Q 3.) b) 364.6 nm
Q 4.) In Balmer series, the line having longest wavelength 656.3 nm which is red in colour is called as Ha line. Then next line with wavelength 486.1 nm in the blue green colour is called as HB line. And the third line with wavelength 434.1 nm in the violet colour is called as Hv line.
Q 5.) The Balmer’s formula is given by
1/wavelength = R*( 1/22 – 1/n2)
Where n = 3, 4, 5,…
Case study 2:
Electrons are revolving around the nucleus in particular stable orbits. The energy of the electron is increasing as we go from the orbit closer to nucleus to outer side. The ground state energy is the lowest energy and it is -13.6 eV for hydrogen atom. Thus, the minimum amount of energy required to remove or free the electron from the ground state is the ionisation energy and it has value +13.6 eV. When electrons jumps from higher energy orbit to lower energy orbit emits energy in the form of photons which are in the form of spectral lines and called as emission lines. The light emitted by the ordinary source of light consist of different wavelength. But the laser light is the monochromatic one which emits light of single wavelength. In case of hydrogen atom, the ground state energy is that energy state for which n = 1. And the states for which n > 1, all are the excited states. Where n shows the principal quantum number.
Questions:
Q 1.) In hydrogen atom, the energy corresponding to principal quantum number n =2 is___
a) -13.6 eV
b) -3.4 eV
c) +13.6 eV
d) +3.4 eV
Q 2.) For ground state of hydrogen atom the value of principal quantum number is___
a) n = 2
b) n = 0
c) n = 1
d) n = infinity
Q 3.) The minimum energy required to remove the electron from the ground state of the hydrogen atom is called as___
a) excitation energy
b) ionisation energy
c) ground state energy
d) excited state energy
Q 4.) The acronym LASER stands for?
Q 5.) If n = infinity then what is the energy of the state and what does it means?
Answer key:
Q 1.) b) -3.4 eV
Q 2.) c) n = 1
Q 3.) b) ionisation energy
Q 4.) The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation.
Q 5.) When the principal quantum number n = infinity then the corresponding state is having energy 0 eV. And this energy of atom is possible only when electron is totally removed from the nucleus and hence it goes to rest.