When radiation strikes the target material in the electrode, electrons are emitted almost instantaneously, even at very low intensities of incident radiation. Let’s examine each of these characteristics. The photoelectric effect has three important characteristics that cannot be explained by classical physics: (1) the absence of a lag time, (2) the independence of the kinetic energy of photoelectrons on the intensity of incident radiation, and (3) the presence of a cut-off frequency. Characteristics of the Photoelectric Effect The voltmeter measures the electric potential difference between the electrodes, and the ammeter measures the photocurrent. The anode and cathode are enclosed in an evacuated glass tube. The potential difference at which the photocurrent stops flowing is called the stopping potential.įigure 6.8 An experimental setup to study the photoelectric effect. The photocurrent gradually dies out and eventually stops flowing completely at some value of this reversed voltage. Suppose that we now reverse the potential difference between the electrodes so that the target material now connects with the positive terminal of a battery, and then we slowly increase the voltage. But when the target material is connected to the negative terminal of a battery and exposed to radiation, a current is registered in this circuit this current is called the photocurrent. When the target material is not exposed to radiation, no current is registered in this circuit because the circuit is broken (note, there is a gap between the electrodes). The electrodes are enclosed in an evacuated glass tube so that photoelectrons do not lose their kinetic energy on collisions with air molecules in the space between electrodes. The potential difference between the electrodes can be increased or decreased, or its polarity can be reversed. Photoelectrons are collected at the anode, which is kept at a higher potential with respect to the cathode. We call this electrode the photoelectrode. The target material serves as the cathode, which becomes the emitter of photoelectrons when it is illuminated by monochromatic radiation. The experimental setup to study the photoelectric effect is shown schematically in Figure 6.8. Electrons that are emitted in this process are called photoelectrons. This phenomenon is known as the photoelectric effect. When a metal surface is exposed to a monochromatic electromagnetic wave of sufficiently short wavelength (or equivalently, above a threshold frequency), the incident radiation is absorbed and the exposed surface emits electrons. Describe how Einstein’s idea of a particle of radiation explains the photoelectric effect.Explain why the photoelectric effect cannot be explained by classical physics.Describe physical characteristics of the photoelectric effect.By the end of this section, you will be able to:
0 kommentar(er)
