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 Multiple Choice QuestionsMultiple Choice Questions

1.

This question has Statement 1 and statement 2. Of the four choices given after the statements, choose the one that best describes the two statements :
Statement 1 :
A metallic surface is irradiated by a monochromatic light of frequency v > v0 (the threshold frequency). The maximum kinetic energy and the stopping potentials are Kmax and V0 respectively. If the frequency incident on the surface is doubled, both the Kmax and V0 are also doubled.
Statement 2 :
The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light.

  • Statement 1 is true, statement2 is false.

  • Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1

  • Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1

  •  Statement 1 is false, Statement 2 is true


D.

 Statement 1 is false, Statement 2 is true

hv = hv0 + kmax
kmax = hv - hv0

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2.

An electron beam is accelerated by a potential difference V to hit a metallic target to produce X-rays. It produces continuous as well as characteristic X-rays.If λmin is the smallest possible wavelength of X-ray in the spectrum, the variation of log λ min with log V is correctly represented in


C.

hc over straight lambda subscript min space equals space eV
1 over straight lambda subscript min space equals space eV over hc
calligraphic l space n open parentheses 1 over lambda subscript m i n end subscript close parentheses space equals </div>		</div>
		<div class= 441 Views

3.

The anode voltage of a photocell is kept fixed. The wavelength λ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows:


D.

As λ is increased, there will be a value of λ above which photoelectrons will cease to come out. So, photocurrent will be zero.

354 Views

4.

STATEMENT – 1
When ultraviolet light is incident on a photocell, its stopping potential is V0 and the maximum kinetic energy of the photoelectrons is Kmax. When the ultraviolet light is replaced by X–rays, both V0 and Kmax increase.

STATEMENT – 2
Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.

  • Statement – 1 is True, Statement – 2 is False.

  • 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 the correct explanation for Statement – 1.

  • Statement – 1 is False, Statement – 2 is True.


A.

Statement – 1 is True, Statement – 2 is False.

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5.

Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see in the figure).



If a strong diffraction peak is observed when electrons are incident at an angle ‘i’ from the normal to the crystal planes with distance’ between them (see figure), de Broglie wavelength λdB of electrons can be calculated by the relationship (n is an integer) 

  • d sin i = nλdB

  • 2d cos i = nλdB

  • 2d sin i = nλdB

  • d cos i = nλdB


D.

d cos i = nλdB

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6.

In a Young's double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is

  • 9.75 mm

  • 15.6 mm

  • 1.56 mm

  • 7.8 mm


D.

7.8 mm

For common maxima
n1λ1 = n2λ2
n1 × 650 = n2 × 520
straight n subscript 1 over straight n subscript 2 space equals space 4 over 5
yd over straight D space equals space nλ
straight y space equals fraction numerator 4 space straight x space 650 space straight x space 10 to the power of negative 9 end exponent space straight x space 1.5 over denominator 0.5 space straight x space 10 to the power of negative 3 end exponent end fraction space
space straight y space equals space 7.8 space mm

315 Views

7.

A photon of frequency v has a momentum associated with it. If c is the velocity of light, the momentum is

  • v /c

  • h v c

  • h v /c2

  • h v /c


D.

h v /c

straight P space equals space fraction numerator straight h over denominator space straight lambda end fraction space equals hv over straight c
340 Views

8.

Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see in the figure).



In an experiment, electrons are made to pass through a narrow slit of width’ comparable to their de Broglie wavelength. They are detected on a screen at a distance ‘D’ from the slit (see figure). 

Which of the following graph can be expected to represent the number of electrons ‘N’ detected as a function of the detector position ‘y’(y = 0 corresponds to the middle of the slit)? 


D.

Diffraction pattern will be wider than the slit

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9.

Match List – I (Fundamental Experiment) with List – II (its conclusion) and select the correct option from the choices given below the list:


List I 
List  II
(A) Franck-Hertz Experiment (i) Particle nature of light
(B) Photo-electric experiment  (ii) Discrete energy levels of atom
 (C) Davison – Germer Experiment  (iii) Wave nature of electron
  (iv) Structure of atom
  
  • A B C
    1 4 3
  • A B C
    2 4 3
  • A B C
    2 1 3
  • A B C
    4 3 2

C.

A B C
2 1 3

a) Frank-Hertz experiments are associated with the discrete energy level of the atom.
b) The photo-electric experiment is associated with particle nature of light.
c) Davisson -Germer experiment is associated with wave nature of the electron.

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10.

The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is (hc = 1240 eV nm)

  • 3.09 eV

  • 1.41 eV

  • 151 eV

  • 1.68 eV


B.

1.41 eV

hc over straight lambda space equals straight ϕ space plus space left parenthesis KE right parenthesis subscript max
rightwards double arrow space 1240 over 400 space equals space straight ϕ plus space 1.68
rightwards double arrow space straight ϕ space equals space 1.41 space eV
171 Views