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CBSE Questions for Class 12 Medical Physics Dual Nature Of Radiation And Matter Quiz 7 - MCQExams.com

The minimum intensity of light to be detected by human eye is 1010W/m2. The number of photons of wavelength 5.6×107m entering the eye, with pupil area 106m2, per second for vision will be nearly
  • 100
  • 200
  • 300
  • 400
If alpha particle, proton and electron move with the same momentum, then their respective de-Broglie wavelengths λα,λp,λe are related as
  • λα=λp=λe
  • λα<λp<λe
  • λα>λp>λe
  • λp>λe>λα
  • λp<λe<λα
De-Broglie wavelength of a body of mass 1kg moving with velocity of 2000m/s is?
  • 3.32×1027oA
  • 1.5×107oA
  • 0.55×1022oA
  • None of these
In a photoemissive cell with exciting wave length λ, the fastest electron has a speed v. If the exciting wavelength is change to 3λ/4, then the speed of the fastest emitted electron will be
  • v(34)12
  • v(43)12
  • Less than v(43)12
  • Greater than v(43)12
The de-Broglie wavelength of a neutron at 27oC is λ. What will be its wavelength at 927oC?
  • λ/2
  • λ/3
  • λ/4
  • λ/9
Threshold wavelength of a metal is 4000oA. If light of wavelength 3000oA irradiates the surface, the maximum kinetic energy of photoelectron is?
  • 1.7eV
  • 1.6eV
  • 1.5eV
  • 1.0eV
The de-Broglie wavelength of an electron and the wavelength of a photon are the same. The ratio between the energy of that photon and the momentum of that electron is (c =velocity of light, h= Planck's constant)
  • h
  • c
  • 1c
  • None of these
The speed of an electron having a wavelength of 1010m is
  • 4.24×106m/s
  • 5.25×106m/s
  • 6.26×106m/s
  • 7.25×106m/s
If alpha particle and deutron move with velocity v and 2v respectively, the ratio of their de-Broglie wavelength will be _____
  • 2:1
  • 1:2
  • 1:1
  • 2:1

The energies of the incident photons are 3,4,5eV. The work functions of the metals are 0.5,1.5,2.5eV. The maximum K.E.s of the photoelectrons are in the ratio:

  • 3:4:5
  • 1:3:5
  • 1:1:1
  • 5:3:1
If the kinetic energy of free electron is made double; the new de-Broglie wavelength will be __________ times that of initial wavelength.
  • 12
  • 2
  • 2
  • 12
Light of wavelength λ falls on a metal having work function hcλ0. Photoelectric effect will take place only if
  • λλ0
  • λ2λ0
  • λλ0
  • λ=4λ0
A body of mass 100g moves at the speed of 36km/h. The de-Broglie wavelength related to it is of the order _________ m.
(h=6.626×1034Js)
  • 1024
  • 1014
  • 1034
  • 1044
If the linear momentum of a particle is 2.2×104kgms1, then what will be its de-Broglie wavelength ? (Take hr. 6.6×1034Js
  • 3×1029m
  • 3×1029nm
  • 6×1029m
  • 6×1029nm
The wavelength λ of a photon and the de-Broglie wavelength of an electron have the same value. Find the ratio of energy of photon of the kinetic energy of electron in terms of mass m, speed of light c and planck constant.
  • λmch
  • hmcλ
  • 2hmcλ
  • 2λmch
What is the photon flux and photon density at 2 m from the lamp?
  • 5.9×1014photonscm2,2×104photonscm2
  • 2×104photonscm2,5.9×1014photonscm2
  • 5.9×1010photonscm2,2×103photonscm2
  • 2×103photonscm2,5.9×1010photonscm2
An electron in an electron microscope with initial velocity v0i enters a region of a stray transverse electric field E0j. The time taken for the change in its de Broglie wavelength from the initial value of λ to λ3 is proportional to.
  • E0
  • 1E0
  • 1E0
  • E0
The approximate number of photons in a femtosecond (1015s) pulse of 600 nanometers wavelenghth light from a 10-kilowatt peak-power dye laser is
  • 103
  • 107
  • 1011
  • 1015
  • 1018
An electron and a photon have same wavelength of 109m. If E is the energy of the photon and p is the momentum of the electron, the magnitude of E/p in SI units is?
  • 1.00×109
  • 1.50×108
  • 3.00×108
  • 1.20×107
The energy of a K-electron in tungsten is 20keV and of an L-electrons is 2keV. The wavelength of X-rays emitted when there is electron jump from L to K shell:
  • 0.3443˚A
  • 0.6887˚A
  • 1.3982˚A
  • 2.78˚A
The formula of kinetic mass of photon is? Where h is Planck's constant, v is frequency of the photon and c is its speed.
  • hvc
  • hvc2
  • hcv
  • c2hv
A particle is projected horizontally with a velocity 10 m/s. What will be the ratio of de-Broglie wavelengths of the particle, when the velocity vector makes an angle 30 and 60 with the horizontal?
  • 3:1
  • 1:3
  • 2:3
  • 3:2
de-Broglie wavelength of atom at TK absolute temperature will be
  • hmKT
  • h3mKT
  • 2mKTh
  • 2mKT
The momentum associated with photon is given by __________.
  • hυ
  • hυc
  • hE
  • hλ
An electron of mass m with an initial velocity V=V0ˆi(V0>0) enters an electric field E=E0ˆi(E0=constant >0) at t=0. If λ0 is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is?
  • λ0(1+eE0mV0t)
  • λ0t
  • λ0(1+eE0mV0t)
  • λ0
A charged particle is accelerated from rest through a certain potential difference. The de Broglie wavelength is λ1 when it is accelerated through V1 and is λ2 when accelerated through V2. The ratio λ1/λ2 is
  • V3/21:V3/22
  • V1/22:V1/21
  • V121:V122
  • V21:V2
An electron of mass m and a photon have same energy E.Find out the ratio of de-Brogile wavelength associated with them is (c- velocity of light)
  • c[2mE]12
  • 1c[2mE]12
  • 1c[E2m]12
  • [E2m]12
A material particle with a rest mass m0 is moving with a velocity of light c. Then determine the wavelength of the de Broglie wave associated with it is.
  • (h/m0c)
  • zero
  • (m0c/h)
The frequencies of X-rays, γ rays and Ultra violet rays are respectively incident on a metal, having work function is 0.5eV. The ratio of maximum speed of emtted electrons is
  • p<q,q>r
  • p>q,q>r
  • p<q,q<r
  • p>q,q<r
About 5% of the power of a 100W light bulb is converted to visible radiation.What is the average intensity of visible radiation at distance of 10 m.
  • 0.4 W / m2
  • 0.04 W / m2
  • 0.004 W / m2
  • 0.0004 W / m2
Choose the correct answer from the alternatives given.
The photon energy in units of eV for electromagnetic waves of wavelength 2 cm is then
  • 2.5×1019
  • 5.2×1016
  • 3.2×1016
  • 6.2×105
A 100W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The  wavelength of the sodium light is 589nm. The number of photons delivered per second to the sphere is
  • 3×1015
  • 3×1010
  • 3×1020
  • 3×1019
A blue lamp mainly emits light of wavelength 4500 ˚A. The lamp is rated at 150 W and 8% of the energy is emitted as visible light. The number of photons emitted by the lamp per second is:
  • 3×1019
  • 3×1024
  • 3×1020
  • 3×1018
Which of the following functions is performed by a photo-electric cell?
  • It converts electrical energy into light
  • It converts light energy into electrical energy
  • It conserves sound energy
  • It converts electrical energy into sound
If h is Plancks constant, the momentum of a photon of wavelength 0.01 Ao is
  • 102h
  • h
  • 102
  • 1012h
A laser beam is for locating distant objects because
  • it is monochromatic
  • it is constant
  • it is not observed
  • it has small angular spread
The maximum value of photoelectric current is called:
  • base current
  • Saturation current
  • collector current
  • emitter current
The energy flux of sunlight reaching the surface of the earth is 1.388×103Wm2. The photons in the sunlight have an average wavelength of 550 nm. How many photons per square metre are incident on the earth per second?
  • 4×1021
  • 4×1034
  • 4×1031
  • 4×1028
The wavelength of light in the visible region is about 390nm for violet colour and about 760nm for red colour. The energy of photon in eV at violet end is
  • 2.32
  • 3.19
  • 1.42
  • 4.13
The linear momentum of a 3 MeV photon is:
  • 0.01 eVsm1
  • 0.02 eVsm1
  • 0.03 eVsm1
  • 0.04 eVsm1
A proton, a neutron, an electron and an α-particle have same energy. Then their de Broglie wavelengths compare as :
  • λp=λn>λe>λα
  • λα<λp=λn<λe
  • λe<λp=λn>λα
  • λe=λp=λn=λα
When the velocity of an electron increases, its de Broglie wavelength:
  • increases
  • decreases
  • remains same
  • may increase or decrease
The de Broglie wavelength of an electron in a metal at 27C is (Givenme=9.1×1031kg,kB=1.38×1023JK1) 
  • 6.2×109m
  • 6.2×1010m
  • 6.2×108m
  • 6.2×107m
A monochromatic light of frequency 3×1014Hz is produced by a LASER, emits the power of 3×103W. Find how many numbers of photons are emitted per second.
  • 1.5×1016
  • 2.5×1016
  • 4.5×1016
  • 8.5×1016
A particle of mass 4m at rest decays into two particles of masses m and 3m having non-zero velocities. The ratio of the de Broglie wavelengths of the particles 1 and 2 is:
  • 12
  • 14
  • 2
  • 1
There are two sources of light, each emitting with a power of 100 W. One emits X-rays of wavelength 1 nm and the other visible light of 500 nm. The ratio of number of photons of X-rays to the photons of visible light of the given wavelength is:
  • 1:500
  • 1:400
  • 1:300
  • 1:200
Relativistic corrections become necessary when the expression for the kinetic energy 12mv2, becomes comparable with mc2, where m is the mass of the particle. At what de Broglie waxelength will relativistic corrections become important for an electron?
  • λ=lnm
  • λ=l0nm
  • λ=l01nm
  • λ=l04nm
Consider the four gases hydrogen, oxygen, nitrogen and helium at the same temperature. Arrange them in the increasing order of the de Broglie wavelengths of their molecules.
  • Hydrogen, helium, nitrogen, oxygen
  • Oxygen, nitrogen, hydrogen, helium
  • Oxygen, nitrogen, helium, hydrogen
  • Nitrogen, oxygen, helium, hydrogen
Two particles A1 and A2 of masses m1,m2(m1>m2) have the same de Broglie wavelength. Then
  • their momenta are the same.
  • their energies are the same.
  • momentum of A1 is less than momentum of A2
  • energy of A1 is more than the energy of A2
A particle A of mass m and initial velocity v collides with a particle B of mass m2 which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths λA and λB after the collision is :
  • λAλB=12
  • λAλB=13
  • λAλB=2
  • λAλB=23
0:0:1


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