An electron of mass m with an initial velocity \(\vec v= v_0\hat i\)\( ( v_o > 0 ) \) enters in an electric field\(\vec E = -E_0 \hat i (E_0 = \text{constant}>0)\) at \(t=0\). If \(\lambda_0\)\(\lambda_0\), is its de-Broglie wavelength initially, then what will be its de-Broglie wavelength at time \(t\)?
1. \(\frac{\lambda_0}{\left(1+ \frac{eE_0}{mv_0}t\right)}\)
2. \(\lambda_0\left(1+ \frac{eE_0}{mv_0}t\right)\)
3. \(\lambda_0 t\)
4. \(\lambda_0\)

Subtopic:  De-broglie Wavelength |
 67%
From NCERT
NEET - 2018
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When the light of frequency \(2\nu_0\) (where \(\nu_0\) is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is \(v_1\). When the frequency of the incident radiation is increased to \(5\nu_0,\) the maximum velocity of electrons emitted from the same plate is \(v_2\). What will be the ratio of \(v_1\) to \(v_2\)?
1. \(1:2\)
2. \(1:4\)
3. \(4:1\)
4. \(2:1\)

Subtopic:  Einstein's Photoelectric Equation |
 73%
From NCERT
NEET - 2018
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What is the de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m?

1. hmkT

2. h3mkT

3. 2h3mkT 

4. 2hmkT

Subtopic:  De-broglie Wavelength |
 80%
From NCERT
NEET - 2017
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The photoelectric threshold wavelength of silver is \(3250\times 10^{-10}~\text{m}\). What will be the velocity of the electron ejected from a silver surface by the ultraviolet light of wavelength \(2536\times 10^{-10}~\text{m}\)? (Given \(h= 4.14\times 10^{-15}~\text{eVs}\) and \(c= 3\times 10^{8}~\text{m/s}\))
1. \(\approx 0.6\times 10^{6}~\text{m/s}\)
2. \(\approx 61\times 10^{3}~\text{m/s}\)
3. \(\approx 0.3\times 10^{6}~\text{m/s}\)
4. \(\approx 0.3\times 10^{5}~\text{m/s}\)

Subtopic:  Einstein's Photoelectric Equation |
 50%
From NCERT
NEET - 2017
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If an electron of mass m with a de-Broglie wavelength of \(\lambda\) falls on the target in an X-ray tube, the cut-off wavelength ( λ0) of the emitted X-ray will be:

1. λ0=2mcλ2h         

2. λ0=2hmc

3. λ0=2m2c2λ3h2       

4. λ0=λ

Subtopic:  De-broglie Wavelength |
From NCERT
NEET - 2016
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Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectron will reach the anode A, if the stopping potential of A relative to C is:

1. +3 V

2. +4 V

3. - 1V

4. -3 V

Subtopic:  Einstein's Photoelectric Equation |
 52%
From NCERT
NEET - 2016
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An electron of mass m and a photon have the same energy E. Find the ratio of de-Broglie wavelength associated with the electron to that associated with the photon. (c is the velocity of light)

1. E2m1/2

2. c2mE1/2

3. 1c2mE1/2

4. 1cE2m1/2

 

Subtopic:  De-broglie Wavelength |
 59%
From NCERT
NEET - 2016
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​​​When a metallic surface is illuminated with radiation of wavelength \(\lambda\), the stopping potential is \({V}\). If the same surface is illuminated with radiation of wavelength \(2\lambda\), the stopping potential is \(\frac{{V}}{4}\). The threshold wavelength for the metallic surface is:
1. \(5\lambda\)
2. \(\frac{5}{2} \lambda\)
3. \(3\lambda\)
4. \(4\lambda\)
Subtopic:  Einstein's Photoelectric Equation |
 76%
From NCERT
NEET - 2016
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