1. What are the key points in the Quantum Theory of Light?
The quantum theory states that particles are waves and waves are particles or in other words, with all particles of matter, waves are associated. I...
2. What is the importance of the Quantum Theory of Light?
The quantum theory of light was the reason why quantum mechanics came into being. Had it not been Einstein who gave the quantum theory of light fir...
3. Which theory best explains every characteristic of light?
Planck's Quantum theory explains all the characteristics of light. According to this theory, light energy is released from the source discreetly in...
4. Define the following terms: Wavelength, Crest, Trough, Amplitude, and Frequency.
Wavelength is the distance between two consecutive waves.The crest is the highest point in a wave.The trough is the lowest point in a wave.The ampl...
5. Write some drawbacks in Newton’s Corpuscular theory, Huygens Wave theory, and Electromagnetic wav...
Some Drawbacks in Corpuscular Theory was:The theory could not explain the phenomena of interference, diffraction, the polarization of light, etc.Ac...
Which theory states that light emitted by luminous objects consists of tiny particles of matter called?
Corpuscular Theory: This theory was given in the seventeenth century by Sir Isaac Newton, which states that light emitted by luminous objects consists of tiny particles of matter called corpuscles. This corpuscle when hit the surface, each particle is reflected back.
What is the behavior of light waves?
Diffraction and interference are one of the behaviors of waves. Maxwell proposed that light is an electromagnetic wave that travels at the speed of light through space. The light frequency is related to its wavelength according to the following relation. (Image to be added soon)
What is light energy?
According to this theory, light energy is released from the source discreetly in the form of energy packets of specific frequencies called photons or quanta. Photons propagate like waves and interact with matter as particles. 2. Define the following terms: Wavelength, Crest, Trough, Amplitude, and Frequency. Wavelength is the distance between two ...
What is the particle behavior of light?
Particle Behaviour of Light. In the Photoelectric experiment, the electron is emitted by the metal with a particular kinetic energy. There exists a critical frequency for every metal, lower than which no electrons are emitted.
What is the theory of light?
The theory states that the velocity of light changes with the change in density of the medium. This theory could explain three main phenomena of light that is the reflection, refraction, and rectilinear propagation of light. Wave Theory: This theory was discovered by Christian Huygens in the seventeenth century.
What is quantum theory?
Introduction to Quantum Theory of Light. Many theories were proposed before the actual discovery of the effects of light. Though light is in existence since the existence of the sun, the effects of light were not discovered muchlater. These theories explain the properties of light and how light transmits. Some of the most popular theories on light ...
Which theory of light travels faster, refraction or interference?
This theory successfully explains the phenomena of reflection, refraction, interference, and diffraction phenomena of light. According to Newton’s theory, light traveling from air to water will increase the speed, while light entering from air to water will decrease the speed. Huygens disagreed with newton’s theory and said ...
What is quantum of light?
A quantum of light is a particle of light which can disappear, giving its energy to an atomic or particle system, or appear, taking energy away from a particle or atomic system. A quantum of light of wavelength λ is the minimum amount of energy which can be stored in an electromagnetic wave at that wavelength, ...
What does amplitude f k mean?
For any given momentum k, the amplitude f ~ ( k) represents the contribution of the sine wave with that frequency to the overall wave. Now, classically the value of [ f ~ ( k)] 2 at each k represents a bona fide contribution to the energy of the light. But the assumption that makes quantum theory quantum is that [ f ~ ( k)] 2 instead represents the probability that there is a contribution to the energy of the light coming from that frequency. The actual contribution that can come from any given frequency can only be one of a set of specific values, which are integer multiples of some unit ℏ c / k. "Quantum" is the word for that unit of energy.
What is a photon in light?
Wikipedia defines a photon as a quantum of light , which it further explains as some kind of a wave-packet. What exactly is a quantum of light?
What is the name of the particle that interacts with matter?
Light (or in general EM radiation) propagates through space as a wave, but it interacts with matter as a particle which we call photons . The Photoelectric effect experimentally showed this (by accident in fact) and in 1905 Einstein provided the proof.
What is the meaning of "back up"?
Making statements based on opinion; back them up with references or personal experience.
Is a photon a wave?
The photon is not related to the wave in any concrete way, the classical wave is a superposition of a large number of photons which are coherent. Just a remark that might be helpful to understand what photon is: the "wavelengths of light" seems to be just a theoretical value calculated with the help of Planck model.
Do photons have energy quanta?
But a quantum of light is often thought of as a discrete amount of energy that the photon of light can have. That is to say the energy is quantized and no longer continuous. So the photons themselves have energy quanta. Share. Improve this answer.
How did Einstein explain the photon effect?
Einstein supported his photon hypothesis with an analysis of the photoelectric effect , a process, discovered by Hertz in 1887, in which electrons are ejected from a metallic surface illuminated by light. Detailed measurements showed that the onset of the effect is determined solely by the frequency of the light and the makeup of the surface and is independent of the light intensity. This behaviour was puzzling in the context of classical electromagnetic waves, whose energies are proportional to intensity and independent of frequency. Einstein supposed that a minimum amount of energy is required to liberate an electron from a surface—only photons with energies greater than this minimum can induce electron emission. This requires a minimum light frequency, in agreement with experiment. Einstein’s prediction of the dependence of the kinetic energy of the ejected electrons on the light frequency, based on his photon model, was experimentally verified by the American physicist Robert Millikan in 1916.
What is blackbody radiation?
Blackbody radiation refers to the spectrum of light emitted by any heated object; common examples include the heating element of a toaster and the filament of a light bulb. The spectral intensity of blackbody radiation peaks at a frequency that increases with the temperature of the emitting body: room temperature objects (about 300 K) emit radiation with a peak intensity in the far infrared; radiation from toaster filaments and light bulb filaments (about 700 K and 2,000 K, respectively) also peak in the infrared, though their spectra extend progressively into the visible; while the 6,000 K surface of the Sun emits blackbody radiation that peaks in the centre of the visible range. In the late 1890s, calculations of the spectrum of blackbody radiation based on classical electromagnetic theory and thermodynamics could not duplicate the results of careful measurements. In fact, the calculations predicted the absurd result that, at any temperature, the spectral intensity increases without limit as a function of frequency.
What is a photoemitting detector?
Photoemissive detectors, such as photomultiplier tubes, collect electrons emitted by the photoelectric effect; in photoconductive detectors the absorption of a photon causes a change in the conductivity of a semiconductor material. A number of subtle influences of gravity on light, predicted by Einstein’s general theory of relativity, ...
How much energy does a photon have?
The energy of a photon of visible light is very small, being on the order of 4 × 10 −19 joule. A more convenient energy unit in this regime is the electron volt (eV). One electron volt equals the energy gained by an electron when its electric potential is changed by one volt: 1 eV = 1.6 × 10 −19 joule. The spectrum of visible light includes photons with energies ranging from about 1.8 eV (red light) to about 3.1 eV (violet light). Human vision cannot detect individual photons, although, at the peak of its spectral response (about 510 nm, in the green), the dark-adapted eye comes close. Under normal daylight conditions, the discrete nature of the light entering the human eye is completely obscured by the very large number of photons involved. For example, a standard 100-watt light bulb emits on the order of 10 20 photons per second; at a distance of 10 metres from the bulb, perhaps 10 11 photons per second will enter a normally adjusted pupil of a diameter of 2 mm.
What is the Compton effect?
His formula matched his experimental findings, and the Compton effect, as it became known, was considered further convincing evidence for the existence of particles of electromagnetic radiation.
How to find the effective mass of a photon?
Through the famous relativity equation E = mc2, a photon of frequency f and energy E = hf can be considered to have an effective mass of m = hf / c2. Note that this effective mass is distinct from the “rest mass” of a photon, which is zero. General relativity predicts that the path of light is deflected in the gravitational field of a massive object; this can be somewhat simplistically understood as resulting from a gravitational attraction proportional to the effective mass of the photons. In addition, when light travels toward a massive object, its energy increases, and its frequency thus increases (gravitational blueshift). Gravitational redshift describes the converse situation where light traveling away from a massive object loses energy and its frequency decreases.
What was Maxwell's first major discovery?
James Clerk Maxwell ’s synthesis of electric, magnetic, and optical phenomena and the discovery by Heinrich Hertz of electromagnetic waves were theoretical and experimental triumphs of the first order. Along with Newtonian mechanics and thermodynamics, Maxwell’s electromagnetism took its place as a foundational element of physics.
What is the intensity of radiation?
The intensity of radiation is a measure of the energy emitted per unit area. A plot of the intensity of blackbody radiation as a function of wavelength for an object at various temperatures is shown in Figure 7.3. 2. One of the major assumptions of classical physics was that energy increased or decreased in a smooth, continuous manner. For example, classical physics predicted that as wavelength decreased, the intensity of the radiation an object emits should increase in a smooth curve without limit at all temperatures, as shown by the broken line for 6000 K in Figure 7.3. 2. Thus classical physics could not explain the sharp decrease in the intensity of radiation emitted at shorter wavelengths (primarily in the ultraviolet region of the spectrum), which was referred to as the “ultraviolet catastrophe.” In 1900, however, the German physicist Max Planck (1858–1947) explained the ultraviolet catastrophe by proposing (in what he called "an act of despair") that the energy of electromagnetic waves is quantized rather than continuous. This means that for each temperature, there is a maximum intensity of radiation that is emitted in a blackbody object, corresponding to the peaks in Figure 7.3. 2, so the intensity does not follow a smooth curve as the temperature increases, as predicted by classical physics. Thus energy could be gained or lost only in integral multiples of some smallest unit of energy, a quantum.
What is blackbody radiation?
One phenomenon that seemed to contradict the theories of classical physics was blackbody radiation, which is electromagnetic radiation given off by a hot object. The wavelength (i.e. color) of radiant energy emitted by a blackbody depends on only its temperature, not its surface or composition.
How does the energy of the emitted electrons depend on the frequency of the light?
When a metal is struck by light with energy above the threshold energy Eo, the number of emitted electrons is proportional to the intensity of the light beam , which corresponds to the number of photons per square centimeter , but the kinetic energy of the emitted electrons is proportional to the frequency of the light. Thus Einstein showed that the energy of the emitted electrons depended on the frequency of the light, contrary to the prediction of classical physics. Moreover, the idea that light could behave not only as a wave but as a particle in the form of photons suggested that matter and energy might not be such unrelated phenomena after all.
What is the quantization hypothesis?
Only five years after he proposed it, Planck’s quantization hypothesis was used to explain a second phenomenon that conflicted with the accepted laws of classical physics. When certain metals are exposed to light, electrons are ejected from their surface (Figure 7.3. 3 ). Classical physics predicted that the number of electrons emitted and their kinetic energy should depend on only the intensity of the light, not its frequency. In fact, however, each metal was found to have a characteristic threshold frequency of light; below that frequency, no electrons are emitted regardless of the light’s intensity. Above the threshold frequency, the number of electrons emitted was found to be proportional to the intensity of the light, and their kinetic energy was proportional to the frequency. This phenomenon was called the photoelectric effect (A phenomenon in which electrons are ejected from the surface of a metal that has been exposed to light).
Why did Planck not explain the quantization of energy?
Initially, his hypothesis explained only one set of experimental data—blackbody radiation. If quantization were observed for a large number of different phenomena, then quantization would become a law.
Which two scientists proposed a connection between the quantized nature of energy and the properties of individual atoms?
Both theories are based on the existence of simple building blocks, atoms in one case and quanta of energy in the other. The work of Planck and Einstein thus suggested a connection between the quantized nature of energy and the properties of individual atoms.
Which region of the spectrum is the ultraviolet catastrophe?
2. Thus classical physics could not explain the sharp decrease in the intensity of radiation emitted at shorter wavelengths (primarily in the ultraviolet region of the spectrum), which was referred to as the “ultraviolet catastrophe.”.
What are the characteristics of a photon?
Based upon the Photon Theory of Light, the photons central characteristics include the following: 1 They maintain movement at a constant velocity, c = 2.9979 x 108 m/s (the speed of light) in free space. 2 They are known to possess zero mass and zero rest energy. 3 They carry energy and momentum, which correlate with the frequency nu (n), and wavelength lamdba (l), (and p, the momentum) of the electromagnetic wave by E = hn and p = h/l. 4 They have the potential of being destroyed or created when radiation is absorbed or emitted. 5 They have the ability to have particle-like interactions, for instance, collisions with electrons and other minute' fragments.
Why is the problem of connecting the wave function with probabilities solely for one photon a non-issue?
Thus, under the new theory, because the photon only marginally goes into each of the two respective components , the problem of connecting the wave function with probabilities solely for one photon becomes a non-issue. In this structure, each photon can then only run interference with itself , eliminating the possible occurrence of two photons.
How does a laser work?
For a Laser to effectively function, it critically needs to have a stimulated emission of light. The stimulated emission of light serves to provide the amplification necessary to properly conduct imaging work.
What is the unique feature of quantum physics?
Unique to quantum physics is the idea that observing something can actually influence the physical processes that are taking place. For instance, in what is known as wave particle duality, light waves act like particles and those particles also act like waves. Said another way, light has properties of both particles and waves, and the behavior of light can be explained by either theory.
Why are laser beams narrow?
3. Collimated. Because they must pass between mirrors numerous times at highly perpendicular angles, the paths which are affected by amplification are known for their ability to resiliently bounce back between mirrored ends of a Laser cavity. For this reason, Laser beams have been designed to be very narrow and limited in their expansion ability.
What is the purpose of quantum physics?
We bring this up when discussing the quantum nature of light to define the term quantum physics so that you understand that its purpose is to show the statistical probability of the electron's location at any given moment. Therefore when the term is combined with "the nature of light," you will have a firm grasp on the general working concept.
Which focuses specifically on the behavior of light (photons)?
The one that focuses specifically on the behavior of light (photons) is known as Quantum Optics. When studying Quantum Optics , you will find the activity patterns of individual photons (light beams) have direct impact upon the outgoing light. The highly specialized and useful device known as the LASER is only one of the many invaluable byproducts ...
