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Dual Nature of Radiation and Matter Test - 25

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Dual Nature of Radiation and Matter Test - 25
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  • Question 1
    1 / -0
    If $$E_{1},E_{2}$$ and $$E_{3}$$ are the kinetic energies of a proton, $$\alpha$$ -particle and deuteron respectively, which all have the same wavelength, then 
    Solution
    The wavelength $$\displaystyle \lambda$$ is same for all three particles.
    $$\displaystyle \lambda = \dfrac {h}{mu}$$
    $$\displaystyle m$$ is mass and $$\displaystyle u$$ is velocity.
    The product $$\displaystyle mu$$ will also be same.
    The particle with higher m value will have lower u value
    The kinetic energy $$\displaystyle = \dfrac {1}{2}mu^2 = \dfrac {1}{2}  \times mu \times u$$
    The particle with lower u value will have lower kinetic energy.
    Thus, the particle with higher $$m$$ value will have lower kinetic energy.
    The increasing order of mass is $$\displaystyle m_1 < m_3 < m_2$$.
    The decreasing order of kinetic energy is $$\displaystyle E_1 > E_3 > E_2$$.
    Note:, $$m_1$$, $$m_2$$ and $$m_3$$ are masses of proton, $$\displaystyle \alpha$$ particle and deuteron respectively.
  • Question 2
    1 / -0
    If electron is having a wavelength of 100 $$A^{0}$$, then momentum is $$(gm \  cm \ s^{-1})$$ units
    Solution
    Momentum =$$\dfrac{h}{\lambda }$$

    $$=\dfrac{6.6\times 10^{-34}}{100\times 10^{-10}}$$

    $$=6.6\times 10^{-26}\ kg\ m/s$$
    $$=6.6\times 10^{-26}\times 1000\times 100\ gm\ cm/s$$     ($$\because $$ 1kg=1000gm 1m=100cm)
    $$=6.6\times 10^{-21}\ gm\ cm/s.$$ 
    So, the answer is option (D).
  • Question 3
    1 / -0
    The de-broglie wavelength of an electron and the wavelength of a photon are same. The ratio between the energy of the photon and the momentum of the electron is
    Solution
    De-broglie wavelength :
    $$\lambda = \dfrac{h}{p}$$

    $$\therefore  \lambda_e= \dfrac{h}{m_{e}V}$$

    and for proton

    $$\lambda _p = \dfrac{hc}{E}$$

    $$given\ \lambda _e = \lambda _p$$ 

    $$\dfrac{h}{m_{e}V} = \dfrac{hc}{E}$$

    $$\dfrac{E}{P_e}= c$$
    So, the answer is option (B).
  • Question 4
    1 / -0
    The wavelength corresponding to a beam of electrons whose kinetic energy is 100 eV is 
    ($$h=6.6\times 10^{-34}$$ Js, $$1eV=1.6\times10^{-19}J$$ J,$$m_{e}= 9.1 \times 10^{-31}$$ kg)
    Solution
    $$\dfrac{1}{2}mv^{2}=\ 100eV$$

    $$mv=\sqrt{2\times 9.1\times 10^{-31}\times 100\times 1.6\times10^{-19}}$$

    $$so\ \lambda  =\dfrac{h}{mv}$$

    $$=\ 1.2\ A^{\circ}$$
    So, the answer is option (C).
  • Question 5
    1 / -0
    A proton and an alpha particle are accelerated through the same potential difference. The ratio of wavelengths associated with proton and alpha particle respectively is :
    Solution
    We know, $$\dfrac{1}{2}mv^2=eV$$

    $$mv = \sqrt{2meV}$$

    $$wavelength, \  \lambda = \dfrac{h}{mv}$$

    $$\lambda _p = \dfrac{h}{\sqrt{2m_{p}q_{p}V}}$$

    $$\lambda _p = \dfrac{h}{\sqrt{2meV}}$$

    $$\lambda _{\alpha} = \dfrac{h}{\sqrt{2m_{\alpha} q_{\alpha}V}}$$

    $$= \dfrac{h}{\sqrt{2\times4m\times2e\times V}}$$

    $$\dfrac{\lambda _p}{\lambda _{\alpha }}  = \dfrac{2\sqrt2}{1}$$

    So, the answer is option (C).
  • Question 6
    1 / -0
    A charged particle drops through V volts. Match the de Broglie wavelength for given particles 
     Particle                                                                         $$\lambda\ in\ A^o$$
    a. Electron e. $$\sqrt{\dfrac{0.0817}{V}}$$
     b. Deuteron f. $$\sqrt{\dfrac{0.0102}{V}}$$
     c. $$\alpha$$ particle g. $$\sqrt{\dfrac{150}{V}}$$
     d. Proton h.$$\sqrt{\dfrac{0.0409}{V}}$$
    .
    Solution
    $$\dfrac{1}{2}mv^{2}=qV$$

    $$mv=\sqrt{2qVm}$$

    $$\lambda =\dfrac{h}{mv}$$

    $$\lambda =\dfrac{h}{\sqrt{2mqV}}$$

    $$\lambda _{e}=\dfrac{h}{\sqrt{2m_e\times e\times V}}$$

    $$\lambda _{e}=\sqrt{\dfrac{150}{V}}$$

    $$\lambda _{\alpha }=\dfrac{h}{\sqrt{2\times 4\times m_p\times
    2\times e\times V}}$$

    $$\lambda _{\alpha }=\sqrt{\dfrac{0.0102}{V}}$$

    $$\lambda _p=\sqrt{\dfrac{0.0817}{V}}$$

    $$\lambda_d\ =\sqrt{\dfrac{0.0409}{V}}$$

    $$\left ( m_d=2m_p\ \ q_{d}=e \right )$$
    So, the answer is option (B).
  • Question 7
    1 / -0
    If $$\lambda_{0} $$ is the de Broglie wavelength for a proton accelerated through a potential difference of 100V, the de Broglie wavelength for $$\alpha $$ -particle accelerated through the same potential difference is
    Solution
    Proton is accelerated through a potential difference 100 V
    $$so,\ \dfrac{1}{2}mv^{2}= e\times 100$$

    $$mv= \sqrt{2m_{p}e\times 100}$$

    $$\lambda _o=\dfrac{h}{\sqrt{2me\times 100}}$$

    $$De \ broglie \ wavelength\ of\ \alpha -\ particle$$

    $$\lambda _{\alpha } = \dfrac{h}{\sqrt{2m_{\alpha }v_{\alpha }\times 100}}$$

    $$\lambda _{\alpha } = \dfrac{h}{\sqrt{2\times 4m\times 2e\times 100}}$$

    $$so\ \lambda _{\alpha} = \dfrac{\lambda _0}{2\sqrt{2}}$$
    So, the answer is option (C).
  • Question 8
    1 / -0
    If the energy of a particle is reduced to one fourth, then the percentage increase in its de Broglie wavelength will be :
    Solution
    We know,

    $$\dfrac{1}{2^{\cdot }}mv^{2}=E$$

    $$mv=\sqrt{2mE}$$         &

    $$\lambda =\dfrac{h}{mv}$$

    $$\lambda'=\dfrac{h}{\sqrt{2mE'}}$$

    $$\lambda ^{'}=\dfrac{h}{\sqrt{2m\dfrac{E}{4}}}$$

    $$\dfrac{\lambda ^{'}}{\lambda }=2$$

    $$\lambda ^{'}=2\lambda $$

    So, the answer is option (C).
  • Question 9
    1 / -0
    Two particles of masses m and 2m have equal kinetic energies. Their de Broglie wavelengths are in the ratio of 
    Solution
    $$\dfrac{1}{2}mv^{2}=E$$

    $$mv=\sqrt{2Em}$$
    De-broglie wavelength

    $$\lambda =\dfrac{h}{mv}$$

    $$\lambda_m=\dfrac{h}{\sqrt{2E\times m}}$$

    $$\lambda_{2m} =\dfrac{h}{\sqrt{2\times E\times 2m}}$$

    $$\dfrac{\lambda_m}{\lambda_{2m}}=\dfrac{\sqrt{2}}{1}$$

    So, the answer is option (D).
  • Question 10
    1 / -0
    If the velocity of a particle is increased three times, then the percentage decrease in its de Broglie wavelength will be :
    Solution
    Wavelength, $$\lambda =\dfrac{h}{mv}$$

    $$\lambda ^{'}=\dfrac{h}{3mv}$$

    $$\dfrac{\lambda ^{'}}{\lambda }=\dfrac{1}{3}$$

    $$\lambda ^{'}=\dfrac{\lambda }{3}$$

    $$\Delta \lambda =\lambda -\dfrac{\lambda }{3}$$

    $$=\dfrac{2\lambda }{3}$$

    $$=66.6$$% decrease in$$\lambda$$

    So, the answer is option (B).
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