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Earn 100

The remote control of a TV emits infra-red light of wavelength 900nm. The TV detector is made of a semiconductor whose band gap is x eV. The detector is shielded by a semiconductor optical filter whose band gap is y eV. From the four options below, select the best option for the TV to function.

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Important Questions on Dual Nature of Radiation and Matter

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Given below are two statements:

Statement I: Two photons having equal linear momenta have equal wavelengths.

Statement II: If the wavelength of the photon is decreased, then the momentum and energy of a photon will also decrease.

In the light of the above statements, choose the correct answer from the options given below.

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A monochromatic source of radiation is operating at 100 W power. The source emits 2×1020 photons per second. The wavelength of light will be h=6.67×10-34 J s
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The wavelength of 1 keV photon is 1.24×10-9 m. What is the frequency of 1 MeV photon?
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A radio transmitter operates at a frequency 880kHz and a power of 10 kW. What is the number of photons emitted per second?
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A 2 mW laser operates at a wavelength of  500 nm . The number of photons that will be emitted per second is:
[Given Planck's constant h=6.6×10-34 J s, speed of light  c=3.0×108 m/s ]
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_____ is the wavelength of photon of energy 35 KeV.

h=6.625×10-34J-s, c=3×108ms-1, 1 eV=1.6×10-19J.
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A potassium chloride crystal has an energy band gap of 6 eV. What wavelength of light for which the crystal is completely transparent? (Assume hc=1242 eV mm)
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If a semiconductor photo diode can detect a photon with a maximum wavelength of 400 nm, then its band gap energy is: Planck's constant h=6.63×10-34 J s 
Speed of light c=3×108 m s-1.
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Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of the same power 200 W. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is:
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A photon of frequency 'v' has a momentum associated with it. If 'c' is the velocity of light then momentum is _______
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A 160 W light source is radiating light of wavelength 6200 A° uniformly in all directions. The photon flux at a distance of 1.8 m is of the order of (Planck's constant=6.63×10-34 J s,
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The energy associated with light of which of the following colours is minimum:
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If the energy of photons corresponding to wavelength of 6000 A is 3.2×10-19 J. The photon energy for wavelength of 4000 A will be _____
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If vgvX and vm, are the speeds of gamma rays, X-rays and microwaves respectively in vacuum, then
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The momentum of an X-ray photon is 3×10-23 kg m s-1. The energy of this photon is
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The momentum of a photon of frequency ν is
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To excite the spectral line of wavelength 4960 A of an atom, an excitation energy of 7.7 eV is required. The ground state energy of the atom is 10.5 eV. The energies of two levels involved in the emission of 4960 A line are (Assume, hc=1240 eV nm, where h is Planck's constant and c is speed of light)
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Light is incident normally on a completely absorbing surface with an energy flux of  25 W cm-2 . If the surface has an area of  25 cm2 , the momentum transferred to the surface in 40min time duration will be:
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A pulse of light of duration 100 ns is absorbed completely by a small object initially at rest. Power of the pulse is 30 mW and the speed of light is 3×108 m s-1. The final momentum of the object is