Question 1

Dark lines in the spectra observed from stellar atmospheres indicate that

Accepted Answer

The dark lines in the spectra indicate that atoms are present in the atmosphere that are absorbing photons of those frequencies, causing a decrease in the intensity of those specific wavelengths. This can be caused by the atoms absorbing the photons and transitioning between energy levels, resulting in the missing frequencies being absorbed.

Question 2

What is the maximum wavelength photon that can produce a pair of tau particles (mass 1.777 GeV/c²) by pair production?

Accepted Answer

The energy threshold for producing a pair of tau particles is given by $E_{th} = 2m_{	au}c^2 = 3.554$ GeV. The energy of a photon is given by $E = hc/\lambda$. Therefore, the maximum wavelength photon that can produce a pair of tau particles is given by $\lambda_{max} = hc/E_{th} \approx 3.49 	imes 10^{-7}$ nm, which corresponds to choice B.

Question 3

An electron and positron, each having kinetic energy 10 MeV, annihilate and produce two photons. What is the wavelength of each photon?

Accepted Answer

The total energy of the electron and positron is given by E = 2(mc^2 + KE), where mc^2 is the rest energy of each particle and KE is the kinetic energy. Since the rest energy of an electron or positron is 0.511 MeV, we have E = 2(0.511 MeV + 10 MeV) = 21.022 MeV.

When the electron and positron annihilate, their total energy is converted into the energy of the two photons. Since each photon has energy E = hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength, we can solve for λ.

We have E = 2hc/λ, so λ = 2hc/E. Plugging in the values, we get:

λ = 2(6.626 x 10^-34 J s)(3 x 10^8 m/s)/(21.022 x 10^6 eV x 1.6 x 10^-19 J/eV)
   = 1.239 x 10^-6 m
   = 0.124 pm

Therefore, the wavelength of each photon is 0.124 pm, which corresponds to answer choice A.

Question 4

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the characteristic x-rays that are produced in such a situation?

Accepted Answer

When a beam of electrons strikes a heavy metal surface, the electrons in the metal atoms are excited to higher energy levels. When they fall back down to their original energy level, they emit x-rays with specific wavelengths that are characteristic of the metal. These wavelengths are independent of the energy of the electron beam used, so there are only a few specific wavelengths produced for a given metal. This is known as characteristic x-ray emission. Therefore, option C is the correct choice.

Question 5

A Compton scattering experiment is performed in which the scattered photons have a minimum energy of 17.2 keV. What was the incident energy of the photons used in this experiment?

Accepted Answer

The minimum energy of the scattered photons in Compton scattering is given by the equation Escat_min = Einc/(1 + (Einc/mc^2)*(1-cos(theta))), where Einc is the incident energy, mc^2 is the rest energy of the electron, and theta is the scattering angle. Since the minimum energy of the scattered photons is given as 17.2 keV, we can set Escat_min = 17.2 keV and solve for Einc. Using theta = 180 degrees (backscattering), we get:

17.2 keV = Einc/(1 + (Einc/511 keV)*(1-cos(180)))

17.2 keV = Einc/(1 + (-Einc/511 keV))

17.2 keV = Einc/(511 keV - Einc)

Multiplying both sides by (511 keV - Einc), we get:

17.2 keV*(511 keV - Einc) = Einc

Simplifying, we get:

8799.2 keV - 17.2 Einc = Einc

18.4 Einc = 8799.2 keV

Einc = 478.2 keV

Therefore, the incident energy of the photons used in this experiment was 478.2 keV. The closest answer choice is B: 18.4 keV.

Question 6

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a shorter wavelength. Which of the below differences is observed?

Accepted Answer

Electrons are ejected from the metal when they absorb photons with enough energy to overcome the metal's work function. A shorter wavelength means higher photon energy. Therefore, the lamp with shorter wavelength photons will provide higher energy photons, which leads to electrons with a higher maximum energy being ejected.

Question 7

Which of the following did the planetary model of the atom fail to explain?

Accepted Answer

The planetary model of the atom, although an improvement over earlier models, failed to explain why electrons in atoms don't radiate all their energy away rapidly. This led to the development of quantum mechanics and the electron cloud model of the atom. Options A, B, and C are related to the Rutherford model of the atom, which preceded the planetary model.

Question 8

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the bremsstrahlung x-rays that are produced in such a situation?

Accepted Answer

Bremsstrahlung x-rays are produced when a beam of electrons decelerate upon striking a heavy metal surface. The resulting x-ray spectrum is continuous and extends from a minimum energy (or wavelength) up to a maximum energy (or wavelength), with the minimum energy being dependent on the energy of the electron beam used. Thus, a continuous range of wavelengths is produced, down to a minimum that depends on the energy of the electron beam used.

Question 9

A photocell is a device that operates using the photoelectric effect. What metal would enable a photocell to be operated using visible light?

Accepted Answer

The metal with the lowest work function (φ) will enable a photocell to be operated using visible light. The work function of cesium is the lowest of the four metals listed, making it the best choice for a photocell that operates using visible light.

Question 10

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a shorter wavelength. What difference is observed in the number of electrons produced per unit time?

Accepted Answer

The answer of Ultraviolet light is shone on a piece...

Question 11

X-rays of wavelength 0.240 nm are scattered from a free electron at rest and the resulting scattered photons have wavelength 0.244 nm. Through what angle did these photons scatter relative to the initial direction?

Accepted Answer

The increase in wavelength ($\Delta \lambda = 0.004$ nm) due to the scattering of X-rays by a free electron can be explained by the Compton effect, which describes the change in wavelength of photons when they are scattered by particles such as electrons. The formula for the Compton shift is $\Delta \lambda = \lambda' - \lambda = \frac{h}{m_e c} (1 - \cos \theta)$, where $h$ is Planck's constant, $m_e$ is the electron mass, $c$ is the speed of light, and $\theta$ is the scattering angle. Given the values, solving for $\theta$ yields an angle close to 130°, indicating that the photons were scattered through this angle relative to their initial direction.

Question 12

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a longer wavelength. If the new photon energy is still sufficient to overcome the work function of the metal and eject electrons, what difference is observed in the number of electrons produced per unit time?

Accepted Answer

The answer of Ultraviolet light is shone on a piece...

Question 13

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. When the speed of the electrons in the beam is increased, this produces

Accepted Answer

The speed of the electrons in the beam is directly related to the energy of the resulting x-rays. As the speed increases, so does the energy of the x-rays produced, leading to higher energy x-rays.

Question 14

Light with the wavelength of peak intensity from a star can just barely produce photoelectrons from manganese (φ = 4.1 eV). What is the temperature of the star?

Accepted Answer

We can use the formula for finding the wavelength of peak intensity: $\lambda_{max} = \frac{2.898 	imes 10^{-3} mK}{T}$.

To find the energy of a photon with this wavelength, we can use the formula $E = hc/\lambda$, where $h$ is Planck's constant and $c$ is the speed of light.

Setting the energy equal to the work function, we get $4.1 = hc/\lambda_{max}$.

Combining these two equations and solving for $T$, we get $T = \frac{2.898 	imes 10^{-3} mK}{4.1 hc}$. Plugging in the values for $h$ and $c$, we get $T = 9600$ K.

Quiz 27: Early Quantum Physics and the Photon

Dark lines in the spectra observed from stellar atmospheres indicate that

What is the maximum wavelength photon that can produce a pair of tau particles (mass 1.777 GeV/c²) by pair production?

An electron and positron, each having kinetic energy 10 MeV, annihilate and produce two photons. What is the wavelength of each photon?

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the characteristic x-rays that are produced in such a situation?

A Compton scattering experiment is performed in which the scattered photons have a minimum energy of 17.2 keV. What was the incident energy of the photons used in this experiment?

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a shorter wavelength. Which of the below differences is observed?

Which of the following did the planetary model of the atom fail to explain?

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the bremsstrahlung x-rays that are produced in such a situation?

A photocell is a device that operates using the photoelectric effect. What metal would enable a photocell to be operated using visible light?

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a shorter wavelength. What difference is observed in the number of electrons produced per unit time?

X-rays of wavelength 0.240 nm are scattered from a free electron at rest and the resulting scattered photons have wavelength 0.244 nm. Through what angle did these photons scatter relative to the initial direction?

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. When the speed of the electrons in the beam is increased, this produces

Light with the wavelength of peak intensity from a star can just barely produce photoelectrons from manganese (φ = 4.1 eV) . What is the temperature of the star?

Quiz 27: Early Quantum Physics and the Photon

Dark lines in the spectra observed from stellar atmospheres indicate that

What is the maximum wavelength photon that can produce a pair of tau particles (mass 1.777 GeV/c2) by pair production?

An electron and positron, each having kinetic energy 10 MeV, annihilate and produce two photons. What is the wavelength of each photon?

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the characteristic x-rays that are produced in such a situation?

A Compton scattering experiment is performed in which the scattered photons have a minimum energy of 17.2 keV. What was the incident energy of the photons used in this experiment?

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a shorter wavelength. Which of the below differences is observed?

Which of the following did the planetary model of the atom fail to explain?

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the bremsstrahlung x-rays that are produced in such a situation?

A photocell is a device that operates using the photoelectric effect. What metal would enable a photocell to be operated using visible light?

X-rays of wavelength 0.240 nm are scattered from a free electron at rest and the resulting scattered photons have wavelength 0.244 nm. Through what angle did these photons scatter relative to the initial direction?

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. When the speed of the electrons in the beam is increased, this produces

Light with the wavelength of peak intensity from a star can just barely produce photoelectrons from manganese (φ = 4.1 eV) . What is the temperature of the star?

What is the maximum wavelength photon that can produce a pair of tau particles (mass 1.777 GeV/c²) by pair production?