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Physics 28 Years Past year papers for NEET/AIPMT Class 12

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The document Notes | EduRev is a part of the NEET Course Physics 28 Years Past year papers for NEET/AIPMT Class 12.
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Q.1. An electron is accelerated through a potential difference of 10,000 V. Its de-Broglie wavelength is, (nearly) : (me = 9 × 10–31 kg)     (2019)
A: 12.2 × 10–13 m
B: 12.2 × 10–12 m
C: 12.2 × 10–14 m
D: 12.2 nm
Ans: B
Solution:

For an electron accelerated through a potential V

 Notes | EduRev

Q.2. An electron of mass m with an initial velocity Notes | EduReventers an electric field  Notes | EduRevE0 = constant > 0) at t = 0. If λ0 is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is :-    (2018)
A:

 Notes | EduRev


B:

 Notes | EduRev
C: λ0t
D: λ0
Ans: 
A
Solution:

 Notes | EduRev
 Notes | EduRev
 Notes | EduRev

Q.3. When the light of frequency 2v0 (where v0 is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is v1. When the frequency of the incident radiation is increased to 5 v0, the maximum velocity of electrons emitted from the same plate is v2. The ratio of v1 to v2 is :-     (2018)
A: 1 : 2
B: 1 : 4
C: 4 : 1
D: 2 : 1
Ans: 
A
Solution:
 Notes | EduRev
 Notes | EduRev

Q.4. The photoelectric threshold wavelength of silver is 3250 × 10–10m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 × 10–10 m is :-     (2017)
(Given h = 4.14 × 10–15 eVs and c = 3 × 108 ms–1)
A: ≈ 0.6 × 106 ms–1
B: ≈ 61 × 103 ms–1
C: ≈ 0.3 × 106 ms–1
D: ≈ 6 × 105 ms
–1
Ans: A
Solution:

 Notes | EduRev

Q.5. When a metallic surface is illuminated with radiation of wavelength λ the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is V/4. The threshold wavelength for the metallic surface is :    (2016)
A: 3λ
B: 4λ
C: 5λ
D: 5/2λ
Ans:
A
Solution:
When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V.
Photoelectric equation can be written as,
 Notes | EduRev
Now, when the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is V/4. So, photoelectric equation can be written as,
 Notes | EduRev
From equations (i) and (ii), we get
 Notes | EduRev
When a metallic surface is illuminated with radiation of wavelength λ stopping potential is V.
Photoelectric equation can be written as,
 Notes | EduRev
Now, when the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is V/4. So, photoelectric equation can be written as,
 Notes | EduRev
From equations (i) and (ii), we get
 Notes | EduRev

Q.6. An electron of mass m and a photon have same energy E. The ratio of de-Broglie wavelengths associated with them is:    (2016)
A:
 Notes | EduRev
B:

 Notes | EduRev
C:

 Notes | EduRev
D: c(2mE)1/2
Ans: 
B
Solution:

Given that electron has a mass m.
De-Broglie wavelength for an electron will be given as,
 Notes | EduRev
where,
h is the Planck's constant, and
p is the linear momentum of electron
Kinetic energy of electron is given by,  Notes | EduRev
 Notes | EduRev
From equation (i) and (ii), we have
 Notes | EduRev
Energy of a photon can be given as,
 Notes | EduRev
Hence, λP is the de-Broglie wavelength of photon.
Now, dividing equation (iii) by (iv), we get
 Notes | EduRev

Q.7. A certain metallic surface is illuminated with monochromatic light of wavelength, λ. The stopping potential for photo-electric current for this light is 3V0. If the same surface is illuminated with light of wavelength 2λ, the stopping potential is V0. The threshold wavelength for this surface for photoelectric effect is :    (2015)
A: λ/6
B: 6λ
C: 4λ
D: λ/4
Ans: 
C
Solution:
We have,

 Notes | EduRev
where W is the work function and (3V0) is the stopping potential when monochromatic light of wavelength λ is used.

 Notes | EduRev
where V0 is the stopping potential when monochromatic light of wavelength 2λ is used.
Subtracting equation (2) from equation (1)
We get,
 Notes | EduRev
 Notes | EduRev
Substituting in equation (2) we get,
 Notes | EduRev
∴   Notes | EduRev
The threshold wavelength is therefore 4λ.

Q.8. Which of the following figures represent the variation of particle momentum and the associated de-Broglie wavelength?    (2015)
A:

 Notes | EduRev
B:

 Notes | EduRev
C:
 Notes | EduRev


D:

 Notes | EduRev
Ans: 
C
Solution:

The de-Broglie wavelength is given by
 Notes | EduRev

This equation is in the form of yx = c, which is the equation of a rectangular hyperbola.
The de-Broglie wavelength is given by
 Notes | EduRev
This equation is in the form of yx = c, which is the equation of a rectangular hyperbola.


Q.9. When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is :     (2014)
A: 1.3 eV
B: 1.5 eV
C: 0.65 eV
D: 1.0 eV
Ans: 
D
Solution:
Original energy of photon be E0
 Notes | EduRev
From equation (i) and (ii)
 Notes | EduRev

Q.10. If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de−Broglie wavelength of the particle is :    (2014)
A: 60
B: 50
C: 25
D: 75
Ans: 
D
Solution:

 Notes | EduRev

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