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A Hot Body is Placed in a Closed Room Maintained at a Lower Temperature. is the Number of Photons in the Room Increasing?

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प्रश्न

A hot body is placed in a closed room maintained at a lower temperature. Is the number of photons in the room increasing?

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उत्तर

As the hot body is placed in a closed room maintained at a lower temperature, there will be transfer of heat in the room through convection and radiation. Heat radiation also consists of photons; therefore, photons will be emitted by the hot body. Hence, the number of photons in the room will increase.

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  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 42: Photoelectric Effect and Wave-Particle Duality - Short Answers [पृष्ठ ३६३]

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एचसी वर्मा Concepts of Physics Volume 1 and 2 [English]
पाठ 42 Photoelectric Effect and Wave-Particle Duality
Short Answers | Q 5 | पृष्ठ ३६३

संबंधित प्रश्‍न

Light of intensity 10−5 W m−2 falls on a sodium photo-cell of surface area 2 cm2. Assuming that the top 5 layers of sodium absorb the incident energy, estimate time required for photoelectric emission in the wave-picture of radiation. The work function for the metal is given to be about 2 eV. What is the implication of your answer?


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?


When the intensity of a light source in increased,
(a) the number of photons emitted by the source in unit time increases
(b) the total energy of the photons emitted per unit time increases
(c) more energetic photons are emitted
(d) faster photons are emitted


Photoelectric effect supports quantum nature of light because
(a) there is a minimum frequency below which no photoelectrons are emitted
(b) the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity
(c) even when the metal surface is faintly illuminated the photoelectrons leave the surface immediately
(d) electric charge of the photoelectrons is quantised


A 100 W light bulb is placed at the centre of a spherical chamber of radius 20 cm. Assume that 60% of the energy supplied to the bulb is converted into light and that the surface of the chamber is perfectly absorbing. Find the pressure exerted by the light on the surface of the chamber.

(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)


In photoelectric effect the photo current ______.


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?


Consider a 20 W bulb emitting light of wavelength 5000 Å and shining on a metal surface kept at a distance 2 m. Assume that the metal surface has work function of 2 eV and that each atom on the metal surface can be treated as a circular disk of radius 1.5 Å.

  1. Estimate no. of photons emitted by the bulb per second. [Assume no other losses]
  2. Will there be photoelectric emission?
  3. How much time would be required by the atomic disk to receive energy equal to work function (2 eV)?
  4. How many photons would atomic disk receive within time duration calculated in (iii) above?
  5. Can you explain how photoelectric effect was observed instantaneously?

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


Which of the following options represents the variation of photoelectric current with property of light shown on the x-axis?






Which three factors are varied to examine how photocurrent behaves?


Which part collects electrons emitted from the metal surface?


Which part provides an entry point for incident radiation?


Which apparatus provides monochromatic radiation for illuminating emitter plate C?


Which apparatus applies a potential difference between the plates?


After applying a potential difference, how is the resulting photocurrent measured?


What happens when the collector is made negative with respect to the emitter?


When are photoelectrons emitted in relation to the threshold frequency?


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