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Dual Nature of Radiation and Matter Test - 58

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Dual Nature of Radiation and Matter Test - 58
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  • Question 1
    1 / -0
    What is the de-Broglie wavelength of the $$\alpha$$- particle accelerated through a potential difference $$V$$
    Solution
    As we know,
    $$\lambda =\dfrac {h}{\sqrt{2mE}}=\dfrac {h}{\sqrt{2m_{\alpha}Q_{\alpha}V}}$$
    On putting $$Q_{\alpha}=2\times 1.6\times 10^{-19}\ C$$
    $$m_{\alpha }=4m_p=4\times 1.67 \times 10^{-27}\ kg\Rightarrow \lambda =\dfrac {0.101}{\sqrt V}\ A^o$$
  • Question 2
    1 / -0
    The kinetic energy of electron and proton is $$10^{-32}\ J$$. Then the relation between their de-Broglie wavelength is 
    Solution
    According to the question,
    By using $$\lambda =\dfrac {h}{\sqrt{2mE}}\ E=10^{-32}\ J$$= Constant for both 
    particles. Hence $$\lambda \propto \dfrac {1}{\sqrt m}$$ Since $$m_p > m_e$$ so $$\lambda_p < \lambda_e$$.
  • Question 3
    1 / -0
    If a photon has velocity $$c$$ and frequency $$v$$, then which of the following represents its wavelength
    Solution
    If a photon has velocity c and frequency v, then
    $$E=\dfrac{hc}{\lambda}\Rightarrow \lambda =\dfrac{hc}{E}$$
  • Question 4
    1 / -0
    The de-Broglie wavelength of a neutron at $$27^oC$$ is $$\lambda$$. What will be its wavelength at $$927^oC$$
    Solution
    As we know,
    $$\lambda_{neutron } \propto \dfrac {1}{\sqrt T}\Rightarrow \dfrac {\lambda_1}{\lambda_2}=\sqrt{\dfrac {T_2}{T_1}}$$

    $$\Rightarrow \dfrac {\lambda}{\lambda_2}=\sqrt{\dfrac{(273+927)}{(273+27)}}=\sqrt{\dfrac{1200}{300}}=2\Rightarrow \lambda_2=\dfrac {\lambda}{2}$$
  • Question 5
    1 / -0
    For moving ball of cricket, the correct statement about de-Broglie wavelength is 
    Solution
    de Broglie wavelength associated with the particle 
    $$\lambda =\dfrac hp$$
    where  h is the Planck's constant
    now we know thwt ,
    $$E=\dfrac12 mv^2$$  and  $$p=mv$$
    by mutiplying by m on both sides we get,
    $$p=\sqrt{2mE}$$
    hence,
    $$\lambda =\dfrac h{\sqrt{2mE}}$$
  • Question 6
    1 / -0
    The mass of the electron varies with
    Solution
    Mass is basically a constant term for any physical application at low velocity. But in accordance with Einstein's theory of relativity, at higher speeds the mass of the particle change according to formula

    $$m=\dfrac{m}{\sqrt{1-(v^2/c^2)}}$$
  • Question 7
    1 / -0
    The de-Broglie wavelength is proportional to 
    Solution
    As we know,
    $$\lambda =\dfrac hp $$

    $$\Rightarrow \lambda \propto \dfrac 1p$$
  • Question 8
    1 / -0
    When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface then
    Solution
    $$\lambda_r > \lambda_y > \lambda_g$$. Here threshold wavelength $$< \lambda_y$$. 
    hence, no electrons are emitted.
  • Question 9
    1 / -0
    de-Broglie wavelength of a body of mass $$m$$ and kinetic energy $$E$$ is given by 
    Solution
    de Broglie wavelength associated with the particle 
    $$\lambda =\dfrac hp$$
    where  h is the Planck's constant
    now we know thwt ,
    $$E=\dfrac12 mv^2$$  and  $$p=mv$$
    by mutiplying by m on both sides we get,
    $$p=\sqrt{2mE}$$
    hence,
    $$\lambda =\dfrac h{\sqrt{2mE}}$$
  • Question 10
    1 / -0
    A proton and an $$\alpha$$ particle are acclerated through a potential difference of $$100\ V$$. The ratio of the wavelength associated with the proton to that associated with an $$\alpha$$- particle is 
    Solution
    As we know,
    $$\lambda =\dfrac{h}{\sqrt{2mQV}}\Rightarrow \propto \dfrac{1}{\sqrt{mQ}}\Rightarrow \dfrac{\lambda_p}{\lambda_{\alpha}}=\sqrt{\dfrac{m_{\alpha}Q_{\alpha}}{m_p Q_p}}$$
    $$=\sqrt{\dfrac{4m_p\times 2Q_p}{m_p\times Q_p}}=2\sqrt 2$$
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