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Physics NEET MCQ
Particle Nature Of Light Mcq
Quiz 10
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Q.1
A photon of energy 8eV is incident on a metal surface of threshold frequency 1.6×1015 Hz. The maximum kinetic energy of photoelectrons emitted is ... [ GUJCET 2008]
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a) 2.8 eV
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b) 4.2 eV
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c)0.8 eV
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d)1.4eV
Explanation
Answer: (d)
Q.2
The photoelectric threshold wavelength for potassium having workfunction of 2eV is ... [GUJCET 2008]
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a) 310.7 nm
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b) 1240 nm
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c)618.7 nm
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d)618.7 mm
Explanation
Answer:(c)
Q.3
Ultraviolet light of wavelength 200 nm is incident on polished surface of Fe. Work function of the surface is 4.71 eV. What will be the stopping potential? [GUJCET 2008]
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a) 2.5 V
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b) 1.5 V
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c) 0.5 V
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d) none of above
Explanation
Answer: (b)
Q.4
The number of photons of wavelength 660 nm emitted per second by an electric bulb of 60W is [ GUJCET 2008]
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a)2 × 1020
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b) 2 × 10-20
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c)1.5 × 1020
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d)3 × 1020
Explanation
power=nhc/λ ( here n is the number of photons emitted per second)Answer: (a)
Q.5
An alpha particle and a deuteron are moving with velocities v and 2v respectively. What will be the ratio of their de_broglie wavelengths? [ GUJCET 2008]
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a) 2:1
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b) 1:√2
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c)√2 : 1
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d)1 : 1
Explanation
Answer: (b)
Q.6
In photoelectric effect, the threshold wavelength of sodium is 5000Å. Find its work function [ GUJCET 2009]
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a) 7.5 eV
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b) 2.5 eV
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c)10 eVV
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d)5 eV
Explanation
Answer:(b)
Q.7
If the linear momentum of a particle is 2.2 × 104 kgm/s then what will be its de-Broglie wavelength [ GUJCET 2009]
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a) 3 × 10-29 m
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b) 3 × 10-29 nm
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c) 6 × 10-29 m
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d) 6 × 10-29 nm
Explanation
Answer: (b)
Q.8
Sodium and Copper have workfunction 2.3eV and 4.5eV respectively. The ratio their threshold wavelength is nearest to ... [AIEEE2002]
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a)1 : 2
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b) 4 :1
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c)2 : 1
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d)1 : 4
Explanation
Answer: (c)
Q.9
Formation of covalent bonds in compound exhibits .... of electron [ AIEEE 2002]
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a) wave nature
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b) particle nature
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c)both wave and particle nature
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d)none of these
Explanation
Answer: (a)
Q.10
According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from metal vs frequency of the incident radiation gives straight line whose slope .... [ AIEEE 2004]
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a)depends on the nature of the material used
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b) depends on the intensity of the radiation
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c)depends both on the intensity of the radiation and the metal used
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d)is same for all metals and independent of the intensity of radiation
Explanation
value of slope is h Answer:(d)
Q.11
Time taken by a photoelectron to come out after the photon strikes is approximately ... [ AIEEE 2006]
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a) 10-4 s
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b) 10-10s
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c) 10-16s
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d) 10-1 s
Explanation
Answer: (b)
Q.12
If a strong diffraction peak is observed when electrons are incident at an angle of i from the normal to crystal planes with distance d between them ( as shown) de-Broglie wavelength of electrons can be calculates by the relationship... ( n is an integer) [ AIEEE 2008]
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a) dsin i=n λ
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b) 2dcos i=n λ
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c)2dsin i=n λ
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d)dcos i=nλ
Explanation
from the figure θ=90 - iFrom Bragg's law path difference n λ=2dsin θfor constructive interference 2d sin(90- i)=n λ 2dcos i=n λ here n=1, 2, 3, ....Answer: (b)
Q.13
Electrons accelerated by potential V are diffracted from a crystal ( as shown). If d=1Å and i=30° V should be
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a) 2000 V
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b) 50 V
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c)500 V
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d)1000 V
Explanation
We know that for n=1Path difference 2dcos i=λ and λ=h / √(2meV) 2d cos i=h / √(2meV) on substituting the values we get V ≈ 50 VAnswer: (b)
Q.14
The threshold frequency for a metallic surface corresponds to an energy of 6.2eV and the stopping potential for a radiation incident on this surface is 5V. The incident radiation lies in the .... [ AIEEE 2006]
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a) UV region
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b) IR region
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c)visible region
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d)X -ray region
Explanation
eVo=hc/λ - φ ∴ hc/λ=6.2+5.0=11.2 eV on substituting values λ=1100 Å which is in the range of UV region Answer:(a)
Q.15
The cathode of a photoelecric cell is changed such that the work function changes from W1 to W2 ( W2 > WIf the current before and after changes are I1 and I2, all other conditions remaining unchanged, then ....( Assume hf > W2)[ CPMT 1992]
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a) I1=I2
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b) I1 < I2
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c) I1 > I2
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d) I1 < I2 < 2I1
Explanation
The work function has no effect on photoelectric current so long as hf > Wo. The photoelecric current is proportional to the intensity of incident light, since there is no change in the intensity of light. Hence I1=I2 Answer: (a)
Q.16
When light of wavelength 300nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however, light of 600nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the to emitters? [ CPMT 1993]
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a)1 : 2
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b) 2 : 1
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c)4 : 1
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d)1 : 4
Explanation
Answer: (b)
Q.17
A electron of mass m, when accelerated through a potential difference V, has de-Broglie wavelength λ. The de-Broglie wavelength associated with a proton of mass M accelerated through the same potential difference, will be ... [CPMT 1995]
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a) λ(M/m)
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b) λ(m/M)
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c) λ√(M/m)
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d)λ√(m/M)
Explanation
Momentum of electron p=√(2meV) and momentum of proton p'=√(2MeV) Answer: (d)
Q.18
If a photon has a velocity c and frequency f, then which of the following represents its wavelength? [ CPMT 1996]
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a) hf/c
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b) hf
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c)hc/E
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d)hf/c2
Explanation
E=hc/λ ∴ λ=hc/E Answer:(c)
Q.19
In a photo emissive cell with exciting wavelength λ, the fastest electron has speed v. If the exciting wavelength is changed to 3λ/4, the speed of the fastest emitted electron will be ... [ CPMT 1998]
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a) v(3/4)1/2
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b) v(4/3)1/2
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c) less than v(4/3)1/2
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d) greater than v(4/3)1/2
Explanation
½ m v2=hc/λ - φ thus v ∝ (hc/λ - φ)1/ similarly v' ∝ (4hc/3λ - φ)1/ since 4hc/3λ > hc/λ speed of the fastest emitted electron will be grater than v(4/3)1/2 Answer: (d)
Q.20
A photo-cell is illuminated by a source of light, which is placed at a distance d from the cell. If the distance become d/2, then number of electrons emitted per second will be ...[ CPMT 2001]
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a)remains same
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b) four times
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c)two times
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d)one-fourth
Explanation
Answer: (b)
Q.21
Particle nature of and wave nature of electromagnetic waves and electrons can be represented by ..[ [AIIMS 2000]
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a) photo electricity and electron microscopy
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b) light is refracted and diffracted
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c)X-ray is diffracted, reflected by thick metal sheet
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d)electrons have small mass, deflected by the metal sheet
Explanation
Answer: (a)
Q.22
In an electron microscope the accelerating voltage is increased from 20kV to 80 kV, the resolving power of the microscope will become..... [ AIIMS 2000]
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a) 2R
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b) R/2
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c)4R
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d)3R
Explanation
We know that λ ∝ 1/√V and Resolving power R ∝ 1/λThus resolving power R ∝ √V potential is increased four times thus resolving power will increase two times Answer:(a)
Q.23
The speed of an electron having wavelength of 10-10m is .... [ AIIMS 2002]
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a) 4.24 × 106 m/s
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b) 5.25 ×106 m/s
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c) 6.25 × 106 m/s
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d) 7.25 × 106 m/s
Explanation
use formula p=h/λ Answer: (d)
Q.24
A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1kV, its kinetic energy will be ....[ AIIMS 2003]
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a)1840 keV
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b) (1/1840) keV
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c)1 keV
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d)920 keV
Explanation
Answer: (c)
Q.25
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if light is ... [ AIIMS 2003]
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a) polarised
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b) of longer wavelength
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c)of shorter wavelength
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d)of higher intensity
Explanation
Answer: (c)
Q.26
If the momentum of a particle is doubled then its d-Broglie wavelength will become... [ AFMC 1998]
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a) unchanged
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b) four times
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c)two times
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d)half time
Explanation
Answer:(d)
Q.27
X-ray region lies between [ JIPMER 1998]
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a) short radio waves and visible light
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b) visible light and ultraviolet region
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c) gamma rays and ultraviolet rays
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d) short radio waves and long radio waves
Explanation
Answer: (c)
Q.28
The wavelenght λ of the Kα X-ray line of an anticathode element of atomic number z is nearly proportional to ...[ MPPMT 1987]
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a)Z2
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b) (Z - 1)2
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c)1/Z-1
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d)1 / (Z-1)2
Explanation
Answer: (d)
Q.29
Both γ-rays and X-rays are electromagnetic waves. the basic difference in them is [ raj.PMT 1997]
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a) The production of X-rays is a nuclear property whereas the production of γ-rays is an atomic property
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b) The production of X-rays is an atomic property whereas the production of γ-rays is a nuclear property
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c)γ rays have less frequency than X-rays
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d)the velocity of γ rays is more than that of X-rays
Explanation
Answer: (b)
Q.30
X-rays passing through a strong uniform magnetic field [ CPMT 1998]
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a) get deflected in the direction of the field
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b) get deflected in the direction opposite to that of field
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c)get deflected in the direction perpendicular to that of the field
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d)do not get deflected at all
Explanation
Answer:(d)
0 h : 0 m : 1 s
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