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P is It Always True that for Two Sources of Equal Intensity, the Number of Photons Emitted in a Given Time Are Equal? - Physics

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प्रश्न

Is it always true that for two sources of equal intensity, the number of photons emitted in a given time are equal?

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उत्तर

Let the source's area be A, and intensity of the source be I. The energy of each emitted photonis E. Then, the number of photons emitted in a given time will be `n = I/(AE)`

If the areas of the sources and the wavelengths of light emitted by the two sources are different, then the number of photons emitted will be different.

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Experimental Study of Photoelectric Effect
  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 20: Photoelectric Effect and Wave-Particle Duality - Short Answers [पृष्ठ ३६३]

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एचसी वर्मा Concepts of Physics Vol. 2 [English] Class 11 and 12
पाठ 20 Photoelectric Effect and Wave-Particle Duality
Short Answers | Q 2 | पृष्ठ ३६३

संबंधित प्रश्‍न

Define the term 'intensity of radiation' in terms of photon picture of light.


The photoelectric cut-off voltage in a certain experiment is 1.5 V. What is the maximum kinetic energy of photoelectrons emitted?


Can we find the mass of a photon by the definition p = mv?


It is found that yellow light does not eject photoelectrons from a metal. Is it advisable to try with orange light or with green light?


The equation E = pc is valid


A photon of energy hv is absorbed by a free electron of a metal with work-function hv − φ.


A beam of white light is incident normally on a plane surface absorbing 70% of the light and reflecting the rest. If the incident beam carries 10 W of power, find the force exerted by it on the surface.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


Find the maximum magnitude of the linear momentum of a photoelectron emitted when a wavelength of 400 nm falls on a metal with work function 2.5 eV.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


When a metal plate is exposed to a monochromatic beam of light of wavelength 400 nm, a negative potential of 1.1 V is needed to stop the photo current. Find the threshold wavelength for the metal.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


The electric field associated with a light wave is given by `E = E_0 sin [(1.57 xx 10^7  "m"^-1)(x - ct)]`. Find the stopping potential when this light is used in an experiment on photoelectric effect with the emitter having work function 1.9 eV.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


A small piece of cesium metal (φ = 1.9 eV) is kept at a distance of 20 cm from a large metal plate with a charge density of 1.0 × 10−9 C m−2 on the surface facing the cesium piece. A monochromatic light of wavelength 400 nm is incident on the cesium piece. Find the minimum and maximum kinetic energy of the photoelectrons reaching the large metal plate. Neglect any change in electric field due to the small piece of cesium present.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


Answer the following question.
Plot a graph of photocurrent versus anode potential for radiation of frequency ν and intensities I1 and I2 (I1 < I2).


In photoelectric effect, the photoelectric current started to flow. This means that the frequency of incident radiations is ______.


Consider a metal exposed to light of wavelength 600 nm. The maximum energy of the electron doubles when light of wavelength 400 nm is used. Find the work function in eV.


Two monochromatic beams A and B of equal intensity I, hit a screen. The number of photons hitting the screen by beam A is twice that by beam B. Then what inference can you make about their frequencies?


The graph shows the variation of photocurrent for a photosensitive metal

  1. What does X and A on the horizontal axis represent?
  2. Draw this graph for three different values of frequencies of incident radiation ʋ1, ʋ2 and ʋ33 > ʋ2 > ʋ1) for the same intensity.
  3. Draw this graph for three different values of intensities of incident radiation I1, I2 and I3 (I3 > I2 > I1) having the same frequency.

How would the stopping potential for a given photosensitive surface change if the frequency of the incident radiation were increased? Justify your answer.


  • Assertion (A): For the radiation of a frequency greater than the threshold frequency, the photoelectric current is proportional to the intensity of the radiation.
  • Reason (R): Greater the number of energy quanta available, the greater the number of electrons absorbing the energy quanta and the greater the number of electrons coming out of the metal.

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