# 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 $\mathrm{}$$$c= 3\times 10^{8}~\text{m/s}$$${}^{}$) 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 |
From NCERT
NEET - 2017
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An electron of mass m with an initial velocity $$\vec v= v_0\hat i$$$\stackrel{}{}$$$( v_o > 0 )$$ enters in an electric field $$\vec E = -E_0 \hat i$$$$(E_0 = \text{constant}>0)$$ at $$t=0$$. If $$\lambda_0$$${\mathrm{}}_{}$$$\lambda_0$$, 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 |
72%
From NCERT
NEET - 2018
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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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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)

$1.$ ${\left(\frac{E}{2m}\right)}^{1/2}$

$2.$ $c{\left(2mE\right)}^{1/2}$

$3.$ $\frac{1}{c}{\left(\frac{2m}{E}\right)}^{1/2}$

$4.$ $\frac{1}{c}{\left(\frac{E}{2m}\right)}^{1/2}$

Subtopic:  De-broglie Wavelength |
59%
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 |
51%
From NCERT
NEET - 2016
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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. ${\lambda }_{0}=\frac{2mc{\lambda }^{2}}{h}$

2. ${\lambda }_{0}=\frac{2h}{mc}$

3. ${\lambda }_{0}=\frac{2{m}^{2}{c}^{2}{\lambda }^{3}}{{h}^{2}}$

4. ${\lambda }_{0}=\lambda$

Subtopic:  De-broglie Wavelength |
From NCERT
NEET - 2016
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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. $\frac{h}{\sqrt{mkT}}$

2. $\frac{h}{\sqrt{3mkT}}$

3. $\frac{2h}{\sqrt{3mkT}}$ 

4. $\frac{2h}{\sqrt{mkT}}$

Subtopic:  De-broglie Wavelength |
80%
From NCERT
NEET - 2017
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