sentence-transformers/squad huggingface dataset:
Passage: The assumption that black-body radiation is thermal leads to an accurate prediction: the total amount of emitted energy goes up with the temperature according to a definite rule, the Stefan–Boltzmann law (1879–84). But it was also known that the colour of the light given off by a hot object changes with the temperature, so that "white hot" is hotter than "red hot". Nevertheless, Wilhelm Wien discovered the mathematical relationship between the peaks of the curves at different temperatures, by using the principle of adiabatic invariance. At each different temperature, the curve is moved over by Wien's displacement law (1893). Wien also proposed an approximation for the spectrum of the object, which was correct at high frequencies (short wavelength) but not at low frequencies (long wavelength). It still was not clear why the spectrum of a hot object had the form that it has (see diagram).

Question: What do scientists assume black body radiation is?

Question: What kind of prediction does the assumption that black body radiation is thermal lead to?

Question: What type of changes in the light a hot object emits as the object's temperature changes?

Question: What law describes the changes in light emitted by a hot object?

Question: What assumption that black-body radiation is what leads to an accurate prediction?

Question: What does the Stefan-Boltzmann law state?

Question: What about a hot object changes with the temperature?

Question: What color is hotter than "red hot"?

Question: What did Wilhelm Wien discover?

Question: What rule predicts that emitted energy increases with temperature?

Question: What characteristic of the light emitted by a hot object changes with temperature?

Question: Who discovered the mathematical relationship between peaks and curves of light at different temperatures?

Question: The rule that adjust the curve at different temperatures is known as what?

Question: Wien's spectrum model could not predict accurate at what end of the spectrum?
Passage: Prior to Planck's work, it had been assumed that the energy of a body could take on any value whatsoever – that it was a continuous variable. The Rayleigh–Jeans law makes close predictions for a narrow range of values at one limit of temperatures, but the results diverge more and more strongly as temperatures increase. To make Planck's law, which correctly predicts blackbody emissions, it was necessary to multiply the classical expression by a complex factor that involves h in both the numerator and the denominator. The influence of h in this complex factor would not disappear if it were set to zero or to any other value. Making an equation out of Planck's law that would reproduce the Rayleigh–Jeans law could not be done by changing the values of h, of the Boltzmann constant, or of any other constant or variable in the equation. In this case the picture given by classical physics is not duplicated by a range of results in the quantum picture.

Question: Before Planck, it was assumed that the energy of a body could take on what value?

Question: The Rayleigh-Jeans law makes close predictions for what amount of values?

Question: What does Planck's law correctly predict?

Question: In making Planck's law, what was in both the numerator and denominator of the formula that was used?

Question: Planck's work disproved what assumption?

Question: What rule predicted narrow range of energy values at lower temperatures?

Question: Planck's law involved what necessary mathematical step to correctly predict blackbody emission?

Question: Changing values of n, the Boltzmann constant, or other variables resulted in learning what about Planck's law?

Question: The disparity between Planck's law and the Rayleigh-Jeans law led to what conclusion?
Passage: The black-body problem was revisited in 1905, when Rayleigh and Jeans (on the one hand) and Einstein (on the other hand) independently proved that classical electromagnetism could never account for the observed spectrum. These proofs are commonly known as the "ultraviolet catastrophe", a name coined by Paul Ehrenfest in 1911. They contributed greatly (along with Einstein's work on the photoelectric effect) to convincing physicists that Planck's postulate of quantized energy levels was more than a mere mathematical formalism. The very first Solvay Conference in 1911 was devoted to "the theory of radiation and quanta". Max Planck received the 1918 Nobel Prize in Physics "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta".

Question: Einstein and what other two individuals revisited the black-body problem in 1905?

Question: Who came up with the term, "ultraviolet catastrophe"?

Question: When did Paul Ehrenfest come up with the name "ultraviolet catastrophe"?

Question: When was the first Solvay Conference held?

Question: Who received the Nobel Prize in Physics in 1918?

Question: What did Rayleigh & Jeans and Einstein prove independently in 1905?

Question: What name did Paul Ehrenfest give to the proofs from Einstein and Rayleigh & Jeans?

Question: When was the first Solvay Conference held?

Question: What was the topic of the first Solvay Conference?

Question: In what year did Planck receive the Nobel Prize in Physics for his discovery of energy quanta?
Passage: The photoelectric effect is the emission of electrons (called "photoelectrons") from a surface when light is shone on it. It was first observed by Alexandre Edmond Becquerel in 1839, although credit is usually reserved for Heinrich Hertz, who published the first thorough investigation in 1887. Another particularly thorough investigation was published by Philipp Lenard in 1902. Einstein's 1905 paper discussing the effect in terms of light quanta would earn him the Nobel Prize in 1921, when his predictions had been confirmed by the experimental work of Robert Andrews Millikan. The Nobel committee awarded the prize for his work on the photo-electric effect, rather than relativity, both because of a bias against purely theoretical physics not grounded in discovery or experiment, and dissent amongst its members as to the actual proof that relativity was real.

Question: Who first observed the photoelectric effect?

Question: When was the photoelectric effect first observed?

Question: Who published the first thorough investigation of the photoelectric effect?

Question: Who received the Nobel Prize in 1921 for his work on the photoelectric effect?

Question: What did Einstein with the 1921 Nobel Prize for?

Question: What is the photoelectric effect?

Question: Who first observed the photoelectric effect?

Question: Einstein's paper on the photoelectric effect earned him the Nobel Prize in what year?

Question: Einstein's photoelectric effect work was rewards as opposed to his work on what other topic?
Passage: Prior to Einstein's paper, electromagnetic radiation such as visible light was considered to behave as a wave: hence the use of the terms "frequency" and "wavelength" to characterise different types of radiation. The energy transferred by a wave in a given time is called its intensity. The light from a theatre spotlight is more intense than the light from a domestic lightbulb; that is to say that the spotlight gives out more energy per unit time and per unit space(and hence consumes more electricity) than the ordinary bulb, even though the colour of the light might be very similar. Other waves, such as sound or the waves crashing against a seafront, also have their own intensity. However, the energy account of the photoelectric effect didn't seem to agree with the wave description of light.

Question: Before Einstein, electromagnetic radiation was considered to behave as what?

Question: What terms describe different types of radiation?

Question: What other types of wave besides light has its own intensity?

Question: What is the energy transferred by a wave in a given time called?

Question: Prior to Einstein's work, light behavior was modeled as what?

Question: What is the name for the amount of energy transfered by a wave in a given time?

Question: What portion of the photoelectric effect was in disagreement with the believed description of light behavior?

Question: What does it mean for a light source to be more intense than another?
Passage: The "photoelectrons" emitted as a result of the photoelectric effect have a certain kinetic energy, which can be measured. This kinetic energy (for each photoelectron) is independent of the intensity of the light, but depends linearly on the frequency; and if the frequency is too low (corresponding to a photon energy that is less than the work function of the material), no photoelectrons are emitted at all, unless a plurality of photons, whose energetic sum is greater than the energy of the photoelectrons, acts virtually simultaneously (multiphoton effect) Assuming the frequency is high enough to cause the photoelectric effect, a rise in intensity of the light source causes more photoelectrons to be emitted with the same kinetic energy, rather than the same number of photoelectrons to be emitted with higher kinetic energy.

Question: What is emitted as a result of the photoelectric effect?

Question: What does the kinetic energy of a photoelectron depend on?

Question: What happens if the photoelectron's frequency is too low?

Question: What is the term used when photoelectrons act virtually at the same time?

Question: What type of energy due photoelectrons emitted due to the photoelectric effect have?

Question: What factor of the initial light source does the energy of the photoelectrons depend on?

Question: When the photon energy is less than the work function of the material the light is shone upon, how many photoelectrons are emitted?

Question: If the photoelectric effect is occuring, increasing the intensity of the light source causes what?
Passage: Niels Bohr introduced the first quantized model of the atom in 1913, in an attempt to overcome a major shortcoming of Rutherford's classical model. In classical electrodynamics, a charge moving in a circle should radiate electromagnetic radiation. If that charge were to be an electron orbiting a nucleus, the radiation would cause it to lose energy and spiral down into the nucleus. Bohr solved this paradox with explicit reference to Planck's work: an electron in a Bohr atom could only have certain defined energies En

Question: Who introduced the first quantized model of the atom?

Question: When was the first quantized model of the atom introduced?

Question: Why was the first quantized model of the atom introduced?

Question: In classical electrodynamics, a charge moving in a circle should do what?

Question: Who modeled the atom in 1913, challenging Rutherford's model?

Question: What was predicted to happen to a nucleus-orbiting electron under Rutherford's model?

Question: What statement did Bohr make about the electron of an atom, citing Planck's work?
Passage: Bohr also introduced the quantity , now known as the reduced Planck constant, as the quantum of angular momentum. At first, Bohr thought that this was the angular momentum of each electron in an atom: this proved incorrect and, despite developments by Sommerfeld and others, an accurate description of the electron angular momentum proved beyond the Bohr model. The correct quantization rules for electrons – in which the energy reduces to the Bohr model equation in the case of the hydrogen atom – were given by Heisenberg's matrix mechanics in 1925 and the Schrödinger wave equation in 1926: the reduced Planck constant remains the fundamental quantum of angular momentum. In modern terms, if J is the total angular momentum of a system with rotational invariance, and Jz the angular momentum measured along any given direction, these quantities can only take on the values

Question: Who introduced the reduced Planck constant?

Question: What is the reduced Planck constant also known as?

Question: Who helped to give the correct quantization rules for electrons in 1925?

Question: Who helped to give the correct quantization rules for electrons in 1926?

Question: According to Heisenberg and Schrödinger, the reduced Planck constant remains what?

Question: Bohr introduced what value as the quantum of angular momentum?

Question: What incorrect belief did Bohr hold about the reduced Planck constant?

Question: What scientist used matrix mechanics to bring electron behavior in line with the Bohr model?

Question: When was the Schrödinger wave equation proposed?
Passage: where the uncertainty is given as the standard deviation of the measured value from its expected value. There are a number of other such pairs of physically measurable values which obey a similar rule. One example is time vs. energy. The either-or nature of uncertainty forces measurement attempts to choose between trade offs, and given that they are quanta, the trade offs often take the form of either-or (as in Fourier analysis), rather than the compromises and gray areas of time series analysis.

Question: What measurable value obeys a similar rule of angular momentum?

Question: What forces measurement attempts to choose between trade-offs, in quanta?

Question: What form do measurement attempt trade-offs for quanta take the form of?

Question: How is uncertainly measured in this experience?

Question: What type of analysis fits the either-or nature of the uncertainty?

Question: What example is given as another paired relationship of uncertainly related to standard deviation?
Passage: The Bohr magneton and the nuclear magneton are units which are used to describe the magnetic properties of the electron and atomic nuclei respectively. The Bohr magneton is the magnetic moment which would be expected for an electron if it behaved as a spinning charge according to classical electrodynamics. It is defined in terms of the reduced Planck constant, the elementary charge and the electron mass, all of which depend on the Planck constant: the final dependence on h1/2 (r2 > 0.995) can be found by expanding the variables.

Question: What is the unit of magentic properties of the electron?

Question: What is the unit of magentic properties of atomic nuclei?

Question: The Bohr magneton is the magnetic moment of an electron under what restriction?

Question: What three terms define the Bohr magneton value?
Passage: In principle, the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons, and this is how its value was first calculated in the early twentieth century. In practice, these are no longer the most accurate methods. The CODATA value quoted here is based on three watt-balance measurements of KJ2RK and one inter-laboratory determination of the molar volume of silicon, but is mostly determined by a 2007 watt-balance measurement made at the U.S. National Institute of Standards and Technology (NIST). Five other measurements by three different methods were initially considered, but not included in the final refinement as they were too imprecise to affect the result.

Question: How was the Planck constant calculated in the early 20th century?

Question: The value quoted here for the Planck constant is based on a measurement in what year?

Question: Where was this measurement made?

Question: What method was was used to obtain the measurement?

Question: One other measure involved the molar volume of what element?
Passage: There are both practical and theoretical difficulties in determining h. The practical difficulties can be illustrated by the fact that the two most accurate methods, the watt balance and the X-ray crystal density method, do not appear to agree with one another. The most likely reason is that the measurement uncertainty for one (or both) of the methods has been estimated too low – it is (or they are) not as precise as is currently believed – but for the time being there is no indication which method is at fault.

Question: What is a main practical difficulty in determining n?

Question: Why does this difficulty occur?

Question: Which method is at fault or the discrepancy?
Passage: The theoretical difficulties arise from the fact that all of the methods except the X-ray crystal density method rely on the theoretical basis of the Josephson effect and the quantum Hall effect. If these theories are slightly inaccurate – though there is no evidence at present to suggest they are – the methods would not give accurate values for the Planck constant. More importantly, the values of the Planck constant obtained in this way cannot be used as tests of the theories without falling into a circular argument. Fortunately, there are other statistical ways of testing the theories, and the theories have yet to be refuted.

Question: Other than the X-ray crystal density method, other methods rely on what two effects?

Question: Why does relying on these effects create concern?

Question: Using Planck constant values from these effects would lead to what logical issue?

Question: What is the saving grace of relying on these theories?
Passage: A watt balance is an instrument for comparing two powers, one of which is measured in SI watts and the other of which is measured in conventional electrical units. From the definition of the conventional watt W90, this gives a measure of the product KJ2RK in SI units, where RK is the von Klitzing constant which appears in the quantum Hall effect. If the theoretical treatments of the Josephson effect and the quantum Hall effect are valid, and in particular assuming that RK = h/e2, the measurement of KJ2RK is a direct determination of the Planck constant.

Question: What is a watt balance?

Question: What value does RK represent?

Question: If the effects are valid, for RK = n/e2, what is the measurement of KJ2RK equal to?
Passage: The gyromagnetic ratio γ is the constant of proportionality between the frequency ν of nuclear magnetic resonance (or electron paramagnetic resonance for electrons) and the applied magnetic field B: ν = γB. It is difficult to measure gyromagnetic ratios precisely because of the difficulties in precisely measuring B, but the value for protons in water at 7002298150000000000♠25 °C is known to better than one part per million. The protons are said to be "shielded" from the applied magnetic field by the electrons in the water molecule, the same effect that gives rise to chemical shift in NMR spectroscopy, and this is indicated by a prime on the symbol for the gyromagnetic ratio, γ′p. The gyromagnetic ratio is related to the shielded proton magnetic moment μ′p, the spin number I (I = 1⁄2 for protons) and the reduced Planck constant.

Question: The gyromagnetic ratio is the constant proportion between the magentic field and what?

Question: How does the water molecule impact the effect of magnetic fields on protons?

Question: What three factors impact the gyromagnetic ratio?

Question: The gyromagnetic ratio is often difficult to determine due to difficulty accurately determining the value of what?
Passage: A further complication is that the measurement of γ′p involves the measurement of an electric current: this is invariably measured in conventional amperes rather than in SI amperes, so a conversion factor is required. The symbol Γ′p-90 is used for the measured gyromagnetic ratio using conventional electrical units. In addition, there are two methods of measuring the value, a "low-field" method and a "high-field" method, and the conversion factors are different in the two cases. Only the high-field value Γ′p-90(hi) is of interest in determining the Planck constant.

Question: How many methods of measuring the gyromagnetic ratio are there?

Question: How do conversion factors compare in "low-field" and "high-field" methods of measuring the gyromagnetic ratio?

Question: Which method is of interest in determining the Planck constant?

Question: Why is the measurement of electric current an issue in the estimate of the gyromagnetic ratio?
Passage: The Faraday constant F is the charge of one mole of electrons, equal to the Avogadro constant NA multiplied by the elementary charge e. It can be determined by careful electrolysis experiments, measuring the amount of silver dissolved from an electrode in a given time and for a given electric current. In practice, it is measured in conventional electrical units, and so given the symbol F90. Substituting the definitions of NA and e, and converting from conventional electrical units to SI units, gives the relation to the Planck constant.

Question: What is the Faraday constant?

Question: How is the Faraday constant determined?

Question: How does the Faraday constant relate to the Planck constant?

Question: How is the Farday constant value quickly calculated?
Passage: The X-ray crystal density method is primarily a method for determining the Avogadro constant NA but as the Avogadro constant is related to the Planck constant it also determines a value for h. The principle behind the method is to determine NA as the ratio between the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance. Crystals of silicon are used, as they are available in high quality and purity by the technology developed for the semiconductor industry. The unit cell volume is calculated from the spacing between two crystal planes referred to as d220. The molar volume Vm(Si) requires a knowledge of the density of the crystal and the atomic weight of the silicon used. The Planck constant is given by

Question: What is the primary method for determining the Avogadro constant?

Question: The Avogadro constant is determined to be the ratio between what two factors in the X-ray crystal density method?

Question: What element is used typically to establish Avogadro's constant?

Question: How is unit cell volume calculated?

Question: Calculating molar volume requires knowledge of what two factors?
Passage: There are a number of proposals to redefine certain of the SI base units in terms of fundamental physical constants. This has already been done for the metre, which is defined in terms of a fixed value of the speed of light. The most urgent unit on the list for redefinition is the kilogram, whose value has been fixed for all science (since 1889) by the mass of a small cylinder of platinum–iridium alloy kept in a vault just outside Paris. While nobody knows if the mass of the International Prototype Kilogram has changed since 1889 – the value 1 kg of its mass expressed in kilograms is by definition unchanged and therein lies one of the problems – it is known that over such a timescale the many similar Pt–Ir alloy cylinders kept in national laboratories around the world, have changed their relative mass by several tens of parts per million, however carefully they are stored, and the more so the more they have been taken out and used as mass standards. A change of several tens of micrograms in one kilogram is equivalent to the current uncertainty in the value of the Planck constant in SI units.

Question: What measurement is deemed most important to redefine in terms of physical constants?

Question: What is the shape of the object that establishes the base unit of the kilogram?

Question: What alloy is the base unit of the kilogram made from?

Question: Where is the base unit for the kilogram kept?