{"id":3988,"date":"2021-06-06T10:08:40","date_gmt":"2021-06-06T10:08:40","guid":{"rendered":"https:\/\/www.guyhowto.com\/?p=3988"},"modified":"2024-02-21T14:05:04","modified_gmt":"2024-02-21T14:05:04","slug":"photoelectric-effect","status":"publish","type":"post","link":"https:\/\/www.guyhowto.com\/photoelectric-effect\/","title":{"rendered":"Photoelectric Effect with MCQs"},"content":{"rendered":"
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Definition of Photo-Electric Effect<\/strong><\/p>\n

The emission of electrons from a metal surface area when the light of ideal frequency is incident on it is called the photoelectric effect The emitted electrons are called photoelectrons.<\/p>\n<\/div>\n

Historical Perspective of Photoelectric Effect<\/strong><\/h5>\n

The photoelectric effect, found by Hertz in 1887, is the basis of some of the most effective techniques capable of examining the electronic structure of condensed-matter systems– the techniques collectively identified as “photoemission spectroscopy.” Even before the advancement of such methods, the photoelectric effect had a fundamental influence on the history of modern-day science.<\/p>\n

Experiment by Heinrich Hertz<\/strong><\/h5>\n

Hertz carried out an experiment in which a spark gap generator was used. The sparks produced between two small metal spheres in a transmitter induce sparks that jump between two different metal spheres in a receiver.<\/p>\n

Hertz found that he could increase the level of sensitivity of his spark gap device by illuminating it with visible or ultraviolet light. Later research studies by J.J. Thomson showed that this increased sensitivity was the outcome of light pushing on electrons– a particle that he discovered in 1897.<\/p>\n

The primary turning points after Hertz’s work were Thompson’s 1897 discovery of the electron, Einstein’s 1905 hypothesis on the photon, and Millikan’s 1918 reluctant experimental validation of Einstein’s hypothesis. Einstein derived the photon hypothesis with a purely thermodynamic argument and utilized it to predict the frequency threshold in the photoelectric effect, which was not experimentally confirmed till the late 1910s.<\/p>\n

Working of Photoelectric Effect<\/strong><\/h5>\n

The target substance works as the anode, which ends up being the emitter of photoelectrons when it is lit up by monochromatic radiation. We call this electrode the photoelectrode. Photoelectrons are collected at the cathode, which is kept at a lower potential with respect to the anode.<\/p>\n

The potential difference between the electrodes can be increased or reduced, or its polarity can be reversed. The electrodes are enclosed in an evacuated glass tube so that photoelectrons do not lose their kinetic energy on collisions with air particles in the area in between electrodes.<\/p>\n

\"Working-Photo-electric\"<\/p>\n

When the target material is not exposed to radiation, no current is observed in this circuit due to the fact that the circuit is broken (because there is a gap in between the electrodes). But when the target material is connected to the negative terminal of a battery and exposed to radiation, a current is observed in this circuit; this presentation is called the photocurrent.<\/p>\n

Suppose that we now reverse the potential difference between the electrodes so that the target substance now gets in touch with the positive terminal of a battery, and after that, we slowly increase the voltage. The photocurrent slowly dies out and eventually stops flowing totally at some value of this reversed voltage.<\/p>\n

Maximum Energy of Photoelectrons<\/strong><\/h5>\n

The maximum energy of electrons can be figured out by reversing the terminals of the battery in the circuit. In this case, the photoelectrons are repelled by anode A and the photoelectrical current decreases. If the potential is made more and more negative then photoelectric current approaches to absolutely zero. Even the electrons of maximum energy are not able to reach the collector plate.<\/p>\n

So, the maximum energy of photoelectron is,<\/p>\n

K.E (max) = V<\/strong>\u1d52 <\/sub><\/strong>e<\/strong><\/p>\n

\u00bd mv2 <\/sup>= V<\/strong>\u1d52 <\/sub><\/strong>e<\/strong><\/p><\/blockquote>\n

Results of Experiment<\/strong><\/h5>\n
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  1. The electrons are emitted with different energies.<\/li>\n
  2. The maximum energy of photoelectrons depends upon the surface area of metal and the frequency of incident light.<\/li>\n
  3. There is a minimum frequency below which no photon emission happens.<\/li>\n
  4. Electrons are discharged spontaneously.<\/li>\n
  5. The variety of released photoelectrons relies on the intensity of light.<\/li>\n<\/ol>\n

    \"Results-photo-electric\"<\/p>\n

    Stopping Potential<\/strong><\/h5>\n

    The negative potential of the anode at which the photoelectric current becomes absolutely zero is called the stopping potential.<\/p>\n

    Threshold Frequency<\/strong><\/h5>\n

    The minimum value of frequency of incident light, at which electrons are emitted from a metal surface area, is called threshold frequency.<\/p>\n

    It varies from metal to metal and denoted by Fo<\/sub>.<\/p>\n

    MCQs<\/h3>\n
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