Dual Nature of radiation and Matter important questions with Answers PDF
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Q.(1)- What should be main characteristics in metals used in thermionic emission?
Answer- metals used in thermionic
emission
(i) should have high melting point
so that they do not melt on heating.
(ii) Should have small
work-function so that at low temperature large number of free electrons are
emitted.
Q.(2)- How electrons of $\beta $ emission is different from photo electric emission?
Answer- They are exactly same particles but have different kinetic energies.
Photo electrons are emitted from metal surface with energy around few electron volts obtained from photons. But beta particles are emitted from nucleus with energy tenth of mega electron volt because $\beta $ emission is a nuclear phenomena and more energy is produced in nuclear phenomena. .
So energy of electrons in $\beta $ emission will be more than that of electrons in photo electric emission.
Q.(3)- Electrons
are emitted by light of constant wave length. If intensity of light is
increased. How will the energy and number of emitted electrons be effected?
Answer- Since rate of electron emission is directly
proportional to intensity of incident light. Hence if intensity of light is
increased then number of emitted electrons will be increased.
But energy of emitted electrons is directly proportional to the
frequency of incident light (not of intensity of incident light).So energy of electrons is not effected by increase in intensity of light.
Q.(4)- What is de-Broglie wave? Write an expression for its wavelength.
Bihar Board- 2013
Answer- Wave associated with moving particles is called de-Broglie wave.
Wavelength of de-Broglie wave = h/p = h/mv
Where h= plank’s constant
P= mv= momentum of the particles
Q.(5)- Define stopping potential.
Bihar Board- 2014
Answer- Stopping potential- potential difference required to stop photoelectric current is called
stopping potential.
* It is denoted by ${{V}_{0}}$.
${{V}_{0}}=\frac{h}{e}\nu
-\frac{{{\varphi }_{0}}}{e}$
h=plank's constant
e=charge of an electron
$\nu $= frequency of incident light
${{\varphi }_{0}}$= work function
Q.(6)- Define threshold frequency, work function, and stopping potential with
reference to photoelectric effect.
Bihar Board- 2014
Answer- Threshold frequency-
Minimum frequency of incident radiation required to cause photoelectric
emission is called threshold frequency.
• The threshold frequency is just able to eject electrons from metal surface
without giving them addition energy. Work function- minimum energy required to remove an electron
from a metal surface is called work function.
• It is denoted by ${{\varphi }_{0}}$.
${{\varphi
}_{0}}=h{{\nu }_{0}}$
Stopping potential- potential difference required to stop photoelectric current is called stopping potential.
* It is denoted by ${{V}_{0}}$.
${{V}_{0}}=\frac{h}{e}\nu -\frac{{{\varphi }_{0}}}{e}$
h=plank's constant
e=charge of an electron
$\nu $= threshold frequency
${{\varphi }_{0}}$= work function
Q.(7)- Show that the de Broglie wavelength of electron of energy E is given by the relation \[\lambda =\frac{h}{\sqrt{2mE}}\].
Bihar Board- 2009
Answer- Kinetic energy of the electron = E
$\frac{1}{2}m{{v}^{2}}=E$
$\frac{1}{2m}\times {{m}^{2}}{{v}^{2}}=E$
$\frac{1}{2m}\times {{P}^{2}}=E$
${{P}^{2}}=2mE$
$P=\sqrt{2mE}$
now, debroglie wavelength of the electron=\[\lambda =\frac{h}{P}\]=$\frac{h}{\sqrt{2mE}}$
chapter 1 ELECTRIC CHARGES AND FIELDS short Q-A
chapter 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
chapter 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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