Light with an energy flux of \(25\times 10^{4}~\text{Wm}^{-2}\) falls on a perfectly reflecting surface at normal incidence. If the surface area is \(15~\text{cm}^2\), then the average force exerted on the surface is:
1. \(1.25\times 10^{-6}~\text{N}\)
2. \(2.5\times 10^{-6}~\text{N}\)
3. \(1.2\times 10^{-6}~\text{N}\)
4. \(3.0\times 10^{-6}~\text{N}\)

Subtopic:  Particle Nature of Light |
 62%
NEET - 2014
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When the energy of the incident radiation is increased by \(20\%\), the kinetic energy of the photoelectrons emitted from a metal surface increases from \(0.5\) eV to \(0.8\) eV. The work function of the metal will be:
1. \(0.65\) eV
2. \(1.0\) eV
3. \(1.3\) eV
4. \(1.5\) eV
Subtopic:  Einstein's Photoelectric Equation |
 67%
From NCERT
NEET - 2014
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What will be the percentage change in the de-Broglie wavelength of the particle if the kinetic energy of the particle is increased to \(16\) times its previous value?
1. \(25\)
2. \(75\)
3. \(60\)
4. \(50\)

Subtopic:  De-broglie Wavelength |
 69%
From NCERT
NEET - 2014
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The wavelength \(\lambda_{e}\) of an electron and \(\lambda_{p}\) of a photon of the same energy \(E\) are related as:
1. \(\lambda_p \propto \lambda^2_e\)
2. \(\lambda_p \propto \lambda_e\)
3. \(\lambda_p \propto \sqrt{\lambda_e}\)
4. \(\lambda_p \propto \frac{1}{\sqrt{\lambda_e}}\)

Subtopic:  De-broglie Wavelength |
 54%
From NCERT
NEET - 2013
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A 200W sodium street lamp emits yellow light of wavelength 0.6 μm. 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) 1.5×1020                               

(2) 6×1018

(3) 62×1020                                 

(4) 3×1019

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)4×1015Hz                               

(2)5×1015Hz

(3)1.6×1015Hz                           

(4)2.5×1015Hz

Subtopic:  Einstein's Photoelectric Equation |
 64%
From NCERT
NEET - 2012
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An \(\alpha\text-\)particle moves in a circular path of radius \(0.83\) cm in the presence of a magnetic field of \(0.25 ~\text{Wb/m}^2\). The de-Broglie wavelength associated with the particle will be:
1. \(1~\mathring{A}\) 2. \(0.1~\mathring{A}\)
3. \(10~\mathring{A}\) 4. \(0.01~\mathring{A}\)
Subtopic:  De-broglie Wavelength |
 57%
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. \(\frac{p}{200}\)
4. \(100p\)

Subtopic:  De-broglie Wavelength |
 61%
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 ν and the nucleus recoils. The recoil

energy will be:

(1) h2ν2/2 Mc2

(2) zero

(3) hν

(4) Mc2-

Subtopic:  De-broglie Wavelength |
 51%
From NCERT
NEET - 2011
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