# A 200W sodium street lamp emits yellow light of wavelength  Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is  (1) $1.5×{10}^{20}$                                (2) $6×{10}^{18}$ (3) $62×{10}^{20}$                                  (4) $3×{10}^{19}$

Subtopic:  Electron Emission |
68%
From NCERT
NEET - 2012
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Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V.The threshold frequency of the material is:

(1)$4×{10}^{15}Hz$

(2)$5×{10}^{15}Hz$

(3)$1.6×{10}^{15}Hz$

(4)$2.5×{10}^{15}Hz$

Subtopic:  Einstein's Photoelectric Equation |
64%
From NCERT
NEET - 2012
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An $$\alpha -$$ particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of $$0.25 \mathrm{~Wb} / \mathrm{m}^2$$. The de-Broglie wavelength associated with the particle will be:

 1 $$1~\mathring {\text{A}}$$ 2 $$0.1~\mathring {\text{A}}$$ 3 $$10~\mathring {\text{A}}$$ 4 $$0.01~\mathring {\text{A}}$$
Subtopic:  De-broglie Wavelength |
56%
From NCERT
NEET - 2012
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If the momentum of an electron is changed by p, then the de-Broglie wavelength associated with it changes by 0.5%. What is the initial momentum of the electron?

1. 200p

2. 400p

3. $\frac{\mathrm{p}}{200}$

4. 100p

Subtopic:  De-broglie Wavelength |
60%
From NCERT
NEET - 2012
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In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by

1. increasing the filament current

2. decreasing the filament current

3. decreasing the potential difference between the anode and filament

4. increasing the potential difference  between the anode and filament

Subtopic:  Davisson & Germer Experiment (OLD NCERT) |
70%
From NCERT
NEET - 2011
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A radioactive nucleus of mass M emits a photon

of frequency $\nu$ and the nucleus recoils. The recoil

energy will be:

(1)

(2) zero

(3) h$\nu$

(4) ${\mathrm{Mc}}^{2}-\mathrm{h\nu }$

Subtopic:  De-broglie Wavelength |
51%
From NCERT
NEET - 2011
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Photoelectric emission occurs only when the incident light has more than a certain minimum

1. wavelength

2. intensity

3. frequency

4. power

Subtopic:  Photoelectric Effect: Experiment |
78%
From NCERT
NEET - 2011
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The threshold frequency for a photo-sensitive metal is  If the light of frequency  is incident on this metal, the cut-off voltage for the photo-electric emission is nearly:

1. 2 V                                        2. 3 V

3. 5 V                                         4. 1 V

Subtopic:  Photoelectric Effect: Experiment |
64%
From NCERT
NEET - 2011
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The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface having a work function of 5.01 eV when ultraviolet light of 200 nm falls on it is:

 1 2.4 V 2 - 1.2 V 3 - 2.4 V 4 1.2 V
Subtopic:  Einstein's Photoelectric Equation |
57%
From NCERT
NEET - 2010
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When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2I what is the number of emitted electrons and their maximum kinetic energy?

 1 N and 2T 2 2N and T 3 2N and 2T 4 N and T
Subtopic:  Photoelectric Effect: Experiment |
81%
From NCERT
NEET - 2010
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