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Define the Term: Threshold Frequency and - Physics

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प्रश्न

Define the term: threshold frequency

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उत्तर

Threshold frequency is the lowest frequency of electromagnetic radiation that will result in the emission of electrons from a specified metal surface.

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2018-2019 (March) 55/1/3

संबंधित प्रश्न

The work function for the following metals is given: 

Na: 2.75 eV; K: 2.30 eV; Mo: 4.17 eV; Ni: 5.15 eV

Which of these metals will not give photoelectric emission for a radiation of wavelength 3300 Å from a He-Cd laser placed 1 m away from the photocell? What happens if the laser is brought nearer and placed 50 cm away?


Let nr and nb be the number of photons emitted by a red bulb and a blue bulb, respectively, of equal power in a given time.


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.


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)


Define the term: stopping potential in the photoelectric effect.


Do all the electrons that absorb a photon come out as photoelectrons?


The work function for a metal surface is 4.14 eV. The threshold wavelength for this metal surface is ______.


If photons of ultraviolet light of energy 12 eV are incident on a metal surface of work function of 4 eV, then the stopping potential (in eV) will be :


Read the following paragraph and answer the questions.

The figure shows the variation of photoelectric current measured in a photocell circuit as a function of the potential difference between the plates of the photocell when light beams A, B, C and D of different wavelengths are incident on the photocell. Examine the given figure and answer the following questions:

  1. Which light beam has the highest frequency and why?
  2. Which light beam has the longest wavelength and why?
  3. Which light beam ejects photoelectrons with maximum momentum and why?

How would the stopping potential for a given photosensitive surface change if the intensity of incident radiation was decreased? Justify your answer.


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