class 12 physics chapter 12 atoms important questions with answers pdf
Dear students class 12 physics chapter 12 atoms important questions with answers pdf have been collected at one place to get you all prepared for your 12th Bihar board exam, as well as for UP board exams ,Jharkhand board exam ,MP board exams ,Rajsthan board exams ,cbse board exams and other board exams. Visit my nawendu classes youtube channel for more help.
Answer- In alpha scattering
experiment, we know that alpha rays at larger
distances from nucleus go (without deflected) in straight lines. Because
repulsive force is very small due to larger distance.
As alpha rays
goes close to nucleus, distance is small so repulsion force is large and they
are deflected at angles larger than 90 degree. So repulsion force between alpha particle
and nucleus is indirectly proportional to square of distance between them.
So
coulomb’s law is true for atomic distances.
Q.(2)- For large
angle of scattering of alpha particles nucleus of atom is responsible. Why not
electron?
Answer- Mass of electron is 1/10000 th of the mass of alpha particle. So electron is very light (of low
mass) in comparison to alpha particle so it cannot scatter alpha particle at large
angles.
Hence nucleus of an atom is responsible for alpha particles scattering at large angles.
Q.(3)- Describe Rutherford's model of atom developed on the basis of his alpha
particle scattering experiment.
Bihar Board- 2009
Answer- read in Nawendu classes notes.
Q.(4)- Describe the two shortcomings of Bohr model of atom.
Bihar Board- 2019
Answer- the two shortcomings of Bohr model are followings
(i) Bohr model is valid only for single electron system like hydrogen,$H{{e}^{+}}$,$L{{i}^{2+}}$, $B{{e}^{3+}}$ etc but when it is applied to other elements the experimental data were different than theoretical calculations.
(ii) Bohr assumed that electron moved in a circular orbit around a nucleus but according to Summerfield orbits are elliptical.
Q.(5)- What do you mean by Paschen series?
Bihar Board- 2021
Answer- Paschen series are the series of lines in the spectrum of the hydrogen atom which corresponds to transition between the state with principal quantum number n=3 and successive higher States.
• Paschen series lie in infrared region.
• These series where named after the German physicist Friedrich paschen, who first observed them in 1908.
Q.(6)- What do you mean by Bohr’s Stable orbit?
Bihar Board- 2020
Answer- According to Bohr, every atom has a number of stable orbits in which an electron can reside without emission of radiation (energy). Angular momentum of an electron in a stable orbit is equal to integer multiple of $\frac{h}{2\pi }$.
$mvr=\frac{nh}{2\pi }$
Q.(7)- State any four important characteristics of laser Ray.
Bihar Board- 2011
OR
Write two main features of laser rays.
Bihar Board- 2013, 2015
Answer- followings are four important characteristics of laser Ray
(i) Laser rays are monochromatic.
(ii) Laser rays are coherent.
(iii) Laser rays are unidirectional.
(iv) Laser rays are collimated.
Q.(8)- Find expression for closest approach for an alpha particle moving towards nucleons with kinetic energy k = ½ mv².
Answer- Let closest approach of alpha particle towards nucleus is at r distance from nucleus.
Charge of nucleus= +Ze
charge of alpha particle=2e
At closest approach, total kinetic energy of alpha particle will convert into electric potential energy of alpha particle and nucleus.
kinetic energy of alpha particle =potential energy of nucleus and alpha particle
\[K=\frac{1}{4\pi
{{\varepsilon }_{0}}}\times \frac{Ze\times 2e}{r}\]
\[K=\frac{1}{4\pi
{{\varepsilon }_{0}}}\times \frac{2Z{{e}^{2}}}{r}\]
\[r=\frac{1}{4\pi
{{\varepsilon }_{0}}}\times \frac{2Z{{e}^{2}}}{K}\]
This is expression for closest approach of alpha particle towards nucleus .
chapter 1 ELECTRIC CHARGES AND FIELDS short Q-Achapter 2 ELECTROSTATIC POTENTIAL AND CAPACITANCE short Q-A
chapter 3 CURRENT ELECTRICITY short Q-A
chapter 4 MOVING CHARGES AND MAGNETISM short Q-A
chapter 5 MAGNETISM AND MATTER short Q-A
chapter 6 ELECTROMAGNETIC INDUCTION short Q-A
chapter 7 ALTERNATING CURRENT short Q-A
chapter 8 ELECTROMAGNETIC WAVES short Q-A
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