CBSE Questions for Class 12 Medical Physics Dual Nature Of Radiation And Matter Quiz 13 - MCQExams.com

The wave nature of particles was studied using diffraction of particle beams by crystal lattices. The wavelength of the waves associated with fast moving particles was found to be in agreement with the de Broglie relation.
For a particle of mass $$m$$ moving with kinetic energy $$E$$, the de Broglie wavelength is
  • $$\displaystyle \dfrac{h}{2mE}$$
  • $$\displaystyle h\sqrt{2mE}$$
  • $$\displaystyle \dfrac{h}{\sqrt{2mE}}$$
  • $$\displaystyle h\sqrt{\dfrac{2}{mE}}$$
A photon of wavelength $$0.1\overset {o}{A}$$ is emitted by a helium atom as a consequence of the emission of photon. The K.E. gained by helium atom is :
  • 0.05eV
  • 1.05 eV
  • 2.05 eV
  • 3.05 eV
De Broglie wavelength of neutrons in thermal equilibrium is (given $$m_n=1.6\times 10^{-27} kg)$$
  • $$30.8/\sqrt T\,\overset {o}{A}$$
  • $$3.08/\sqrt T\,\overset {o}{A}$$
  • $$0.308/\sqrt T\,\overset {o}{A}$$
  • $$0.0308/\sqrt T\,\overset {o}{A}$$
A particle of mass $$M$$ at rest decays into two particles of masses $$m _ { 1 } \text { and } m _ { 2 }$$ having non zero velocities. The ratio of the de-Broglie wavelengths of the particles $$\lambda _ { 1 } / \lambda _ { 2 }$$ is
  • $$m _ { 1 } / m _ { 2 }$$
  • $$m _ { 2 } / m _ { 1 }$$
  • 1.0
  • $$\sqrt { m _ { 2 } } / \sqrt { m _ { 1 } }$$
Which of the following graphs correctly represents the variation of particle momentum with associated de Broglie wavelength?
An $$\alpha-particle$$ and a proton are fired through the same magnetic field which is perpendicular to their velocity vectors. The $$\alpha-particle$$ and the proton move such that radius of curvature of their paths is same. Find the ratio of their de Broglie wavelengths :
  • $$2:3$$
  • $$3:4$$
  • $$5:7$$
  • $$1:2$$
A modern 200 W sodium street lamp emits yellow light of wavelength $$0.6\mu m$$. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is :
  • $$62\times 10^{20}$$
  • $$3\times 10^{19}$$
  • $$1.5\times 10^{20}$$
  • $$6\times 10^{18}$$
The human eye can barely detect a yellow light $$(\lambda =6000\overset {o}{A})$$ that delivers $$1.7\times 10^{-18}$$ W to the retina. The number of photons per second falling on the eye is nearest to
  • $$5\times 10^9$$
  • 5000
  • 50
  • 5
A homogeneous ball $$(mass=m)$$ of ideal black material at rest is illuminated with a radiation having a set of photons $$(wavelength=\lambda)$$, each with the same momentum and the same energy. The rate at which photons fall on the ball is n. The linear acceleration of the ball is:
  • $$m\lambda / nh$$
  • $$nh/m\lambda$$
  • $$nh/(2\pi)(m\lambda)$$
  • $$2pm\lambda / nh$$
The eye can detect $$5\times 40^4$$ photons $$(m^2s)^{-1}$$ of green light $$(\lambda=5000\overset {o}{A})$$, while ear can detect $$10^{-13}W m^{-2}$$. As a power detector, which is more sensitive and by what factor?
  • Eye is more sensitive and by a factor of 5.00
  • Ear is more sensitive by a factor of 5.00
  • Both are equally sensitive
  • Eye is more sensitive by a factor of $$10^{-1}$$
An electron of mass $$m_e$$ and a proton of mass $$m_p$$ are accelerated through the same potential difference. The ratio of the de Broglie wavelength associated with an electron to that associated with proton is
  • 1
  • $$m_p /m_e$$
  • $$m_e/m_p$$
  • $$\sqrt {m_p/m_e}$$
A sensor is exposed for time t to a lamp of power P placed at a distance l. The sensor has an opening that is 4d in diameter. Assuming all energy of the lamp is given off as light, the number of photons entering the sensor if the wavelength of light is $$\lambda$$ is
  • $$N=P\lambda d^2t/hcl^2$$
  • $$N=4P\lambda d^2t/hcl^2$$
  • $$N=P\lambda d^2t/4hcl^2$$
  • $$N=P\lambda d^2t/16hcl^2$$
The kinetic energy of a particle is equal to the energy of a photon. The particle moves at 5% of the speed of light. The ratio of the photon wavelength to the de Broglie wavelength of the particle is
[No need to used relativistic formula for the particle.]
  • $$40$$
  • $$4$$
  • $$2$$
  • $$80$$
A laser used to weld detached retinas emits light with a wavelength of $$652nm$$ in pulses that are $$20.0ms$$ in duration. The average power during each pulse is $$0.6 W$$. Then
  • The energy of each photon is $$3.048\times 10^{19} J$$
  • The energy content in each pulse is $$12 mJ$$
  • The number of photons in each pulse is nearly $$4\times 10^{15}$$
  • The energy of each photon is nearly $$1.9 eV$$
A 100 W point source emits monochromatic light of wavelength $$6000\overset {o}{A}$$. Calculate the photon flux (in SI unit) at a distance of 5 m from the source. Given $$h=6.6\times 10^{34}$$ J s and $$C=3\times 10^8 ms^{-1}$$
  • $$10^{15}$$
  • $$10^{18}$$
  • $$10^{20}$$
  • $$10^{22}$$
The light sensitive compound on most photographic films is silver bromide AgBr. A film is exposed when the light energy absorbed dissociates this molecule into its atoms. The energy of dissociation of AgBr is $$10^5 J mol^{-1}$$. For a photon that is just able to dissociate a molecule of AgBr, the photon energy is
  • 1.04 eV
  • 2.08 eV
  • 3.12 eV
  • 4.16 eV
 Determine the number of photons emitted by the laser each second.
  • $$3.18\times 10^{15}$$
  • $$4.5\times 10^{16}$$
  • $$1.2\times 10^{15}$$
  • $$2.9\times 10^{17}$$
A photon has same wavelength as the de Broglie wavelength of electrons. Given $$C=$$ speed of light, $$v=$$ speed of electron. Which of the following relation is correct? [Here $$E_e=$$ kinetic energy of electron, $$E_{ph}=$$ energy of photon, $$P_e=$$ momentum of electron and $$P_{ph}=$$ momentum of photon]
  • $$E_e/E_{ph}=2C/v$$
  • $$E_e/E_{ph}=v/2C$$
  • $$P_e/P_{ph}=2C/v$$
  • $$P_e/P_{ph}=C/v$$
Two identical non-relativistic particles A and B move at right angles to each other, processing de Broglie wavelengths $$\lambda_1$$ and $$\lambda_2$$ respectively. The de Broglie wavelength of each particle in their centre of mass frame of reference is :
  • $$\lambda_1+\lambda_2$$
  • $$2\lambda_1\lambda_2/(\sqrt {\lambda_1^2+\lambda_2^2})$$
  • $$\lambda_1\lambda_2/(\sqrt {|\lambda_1^2+\lambda_2^2|})$$
  • $$(\lambda_1+\lambda_2)/2$$
The human eye is most sensitive to green light of wavelength 505 nm. Experiments have found that when people are kept in a dark room until their eyes adapt to the darkness, a single photon of green light will trigger receptor cells in the rods of the retina. The velocity of typical bacterium of mass $$9.5\times 10^{-12}$$g, if it had absorbed all energy of photon, is nearly:
  • $$9\times10^{-3} ms^{-1}$$
  • $$10^{8} ms^{-1}$$
  • $$10^{-10} ms^{-1}$$
  • $$10^{-13} ms^{-1}$$
Two electrons are moving with same speed $$v$$. One electron enters a region of uniform electric field while the other enters a region of uniform magnetic field, when after some time de Broglie wavelengths of two are $$\lambda_1$$ and $$\lambda_2$$, respectively. Now :
  • $$\lambda_1 < \lambda_2$$
  • $$\lambda_1=\lambda_2$$
  • $$\lambda_1 > \lambda_2$$
  • $$\lambda_1$$ can be greater than or less than $$\lambda_2$$
The magnitude of the de-Broglie wavelength $$(\lambda)$$ of electron (e), proton (p), neutron (n) and $$\alpha$$-particle $$(\alpha)$$ all having the same energy of 1MeV, in the increasing order will follow the sequence
  • $$\lambda _e, \lambda _p, \lambda _n, \lambda _\alpha $$
  • $$\lambda _e, \lambda _n, \lambda _p, \lambda _\alpha $$
  • $$\lambda _\alpha , \lambda _n, \lambda _p, \lambda _e $$
  • $$\lambda _p , \lambda _e, \lambda _\alpha , \lambda _n $$
If $$10,000V$$ are applied across an X-ray tube, find the ratio of wavelength of the incident electrons and  the shortest wavelength of X-ray coming out of the X-ray tube, given $$e/m$$ of electron $$=1.8\times10^{11}\space C\space kg^{-1}$$.
  • $$1:10$$
  • $$10:1$$
  • $$5:1$$
  • $$1:5$$
The electron cannot exist inside the nucleus because
  • de-Broglie wavelength associated with electron in $$\beta$$ -decay is much less than the size of nucleus
  • de-Broglie wavelength associated with electron in $$\beta$$ -decay is much greater than the size of nucleus
  • de-Broglie wavelength associated with electron in $$\beta$$ -decay is equal to the size of nucleus
  • de-Broglie negative charge cannot exist in the nucleus
The number of photons that each pulse delivers to the blemish is
  • $$1.5\times 10^{16}$$
  • $$1.5\times 10^{8}$$
  • $$3\times 10^{16}$$
  • $$3\times 10^{8}$$
The circumference of the second Bohr orbit of electron in hydrogen atom is $$600nm$$. The potential difference that must be applied between the plates so that the electrons have the de Broglie wavelength corresponding in this circumference is
  • $$10^{-5}\space V$$
  • $$\displaystyle\frac{5}{3}\times10^{-5}\space V$$
  • $$5\times10^{-5}\space V$$
  • $$3\times10^{-5}\space V$$
A particle of mass M at rest decays into two particles of masses $$m_1$$ and $$m_2$$, having non-zero velocities. The ratio of the de Broglie wavelengths of the particles $$\lambda_1/\lambda_2$$ is :
  • $$m_1/m_2$$
  • $$m_2/m_1$$
  • $$1$$
  • $$\sqrt {m_2}/\sqrt {m_1}$$
The energy of the photons causing the photoelectric emission is
  • $$2.55\space eV$$
  • $$0.73\space eV$$
  • $$1.82\space eV$$
  • Information insufficient
The de-Broglie wavelength of a neutron at $$972^o C$$ is $$\lambda$$.
What will be its wavelength at $$27^o C$$ ? 
  • $$\dfrac{\lambda}{2}$$
  • $$\lambda$$
  • $$2\lambda$$
  • $$4\lambda$$
A steel ball of mass m is moving with a kinetic energy 'K'. The de-Broglie wavelength associated with the ball is 
  • $$\dfrac{h}{2mK}$$
  • $$\sqrt{\dfrac{h}{2 mk}}$$
  • $$\dfrac{h}{\sqrt{2mK}}$$
  • Meaningless
Two insulating plates are both uniformly charged in such a way that the potential difference between them is $$V_2-V_1=20 V$$. (i.e., plate 2 is at a higher potential). The plates are separated by $$d=0.1$$ m and can be treated as infinitely large. An electron is released from rest on the inner surface of plate $$1$$. What is its speed when it hits plate $$2$$?
$$(e=1.6 \times 10^{-19} C, m_e=9.11 \times 10^{-31} kg)$$
  • $$2.65 \times 10^6 m/s$$
  • $$7.02 \times 10^{12} m/s$$
  • $$1.87 \times 10^6 m/s$$
  • $$32 \times 10^{-19} m/s$$
In case of electrons and photons having the same wavelength. What is same for them ?
  • Energy
  • Velocity
  • Momentum
  • Angular momentum
If 5% of the energy supplied to a bulb is radiated as visible light, the number of visible quanta emitted per second by a 100W bullb, assuming the wavelength of visible light to be $$5.6 \times 10^{-5}cm$$, is
  • $$1.4 \times 10^{19}$$
  • $$1.4 \times 10^{20}$$
  • $$2 \times 10^{19}$$
  • $$2 \times 10^{20}$$
For a photoelectric cell, the graph showing the variation of cut off voltage $$(V_0)$$ with frequency $$(v)$$ of incident light is:-
The de-Broglie  wavelength of a proton $$(mass=1.6 \times 10 ^{-27} kg)$$ accelerated through a potential difference of 1 kV is :
  • $$600 \mathring {A}$$
  • $$0.9 \times 10^{-12}m$$
  • $$7 \mathring { A } $$
  • $$0.9 \times 10^{-19}nm$$
A material particle with a rest mass $$'m_0\ '$$ is moving with speed of light 'c'. The de-Broglie wavelength associated is given by
  • $$\dfrac{h}{m_0c}$$
  • $$\dfrac{m_0c}{h}$$
  • Zero
  • $$\infty $$
A monochromatic source of light operating at 200 W emits $$4 \times 10^{20}$$ photons per second. Find the wavelength of light.
  • $$400 nm$$
  • $$200 nm$$
  • $$4 \times 10 ^{-10} \mathring { A } $$
  • None of these
A particle with rest mass $$'m_0\ '$$ is moving with speed of light 'c'. The de-Broglie wavelength associated with it will be
  • $$\infty $$
  • Zero
  • $$m_0 \, c/h$$
  • $$hv/m_0c$$
If $$E_1, E_2, E_3$$ are the respective kinetic energies of an electron, an $$\alpha$$-particle and a proton, each having the same de-Broglie wavelength, then
  • $$E_1 > E_3 > E_2$$
  • $$E_2 > E_3 > E_1$$
  • $$E_1 > E_2 > E_3$$
  • $$E_1 = E_2 = E_3$$
The de - Broglie wavelength associated with the electron in the $$n=4$$ level is :
  • half of the de-Broglie wavelength of the electron in the ground state
  • four times the de-Broglie wavelength of the electron in the ground state
  • $$1/4^{th}$$ of the de-Broglie wavelength of the electron in the ground state
  • two times the de-Broglie wavelength of the electron in the ground state
Saturation current in second case is
  • $$\displaystyle 9.2\mu A $$
  • $$\displaystyle 13.3\mu A $$
  • $$\displaystyle 15.1\mu A $$
  • $$\displaystyle 19.4\mu A $$
Each question contains statement 1 and statementChoose the correct answer (only one option is  correct) from the following options.

Statement-1 : The de-Broglie wavelength of a molecule (in a sample of ideal gas) varies inversely as the square root of absolute temperature.
Statement-2 : The rms velocity of a molecule (in a sample of ideal gas) depends on temperature.
  • Statement-1 is false, Statement -2 is true
  • Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for statement-1
  • Statement -1 is true, Statement-2 is true; Statement -2 is not correct explanation for statement-1
  • Statement-1 is true, Statement -2 is false
If velocity of a particle A is 50% of velocity of particle B and mass of B is 25% of mass of A then de-Broglie wavelength of B if wavelength of A is $$2\mathring A$$
  • $$4A^{\circ}$$
  • $$20A^{\circ}$$
  • $$6.0A^{\circ}$$
  • none
An LED (Light Emitting Diode) is constructed from a p-n junction based on a certain $$Ga-As-P$$ semi-conducting material whose energy gap is $$1.9eV$$.What is the wavelength of the emitted light?
  • $$650nm$$
  • $$65\mathring { A } $$
  • $$800nm$$
  • $$8000\mathring { A } $$
The de-Broglie wavelength of an electron (mass $$1\times { 10 }^{ -30 }kg$$, charge$$=1.6\times { 10 }^{ -19 }\ C$$) with kinetic energy of $$200eV$$ is: (Planck's constant $$6.6\times { 10 }^{ -34 }J$$):
  • $$9.60\times { 10 }^{ -11 }m$$
  • $$8.25\times { 10 }^{ -11 }m$$
  • $$6.25\times { 10 }^{ -11 }m$$
  • $$5.00\times { 10 }^{ -11 }m$$
A hydrogen atom makes a transition from $$n=3$$ to $$(n=1)$$ .The momentum of the emitted photon is $${h=Planck' constant,R=Rydberg constant)
  • $$\frac { 8hR }{ 9 } $$
  • $$\frac { 9hR }{ 9 } $$
  • $$\frac { 8h }{ 9 } $$
  • $$\frac { 8R }{ 9 } $$
When a microgram of matter is converted to energy, the amount of energy released will be?
  • $$9\times 10^{14}$$J
  • $$9\times 10^{10}$$J
  • $$9\times 10^7$$J
  • $$9\times 10^4$$J
The de-Broglie wavelength of an electron is the same as that of a $$50 keV$$ X-ray photon. The ratio of the energy of the photon to the kinetic energy of the electron is (the energy equivalent of electron mass is $$0.5 MeV$$):
  • $$1 : 50$$
  • $$1 : 20$$
  • $$20 : 1$$
  • $$50 : 1$$
The de-Broglie wavelength of an electron moving with a velocity of $$1.5\times 10^8\ m/s$$ is equal to that of a photon. The ratio of kinetic energy of the electron to that of the photon $$(c=3\times 10^8\ m/s)$$:
  • $$2$$
  • $$4$$
  • $$\displaystyle\frac{1}{2}$$
  • $$\displaystyle\frac{1}{4}$$
A proton when accelerated through a potential difference of $$V$$, has a de Broglie wavelength $$\lambda$$ associated with it. If an alpha particle is to have the same de Broglie wavelength $$\lambda$$, it must be accelerated through a potential difference of:
  • $$\displaystyle\frac{V}{8}$$
  • $$\displaystyle\frac{V}{4}$$
  • $$4V$$
  • $$8V$$
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