Deck 27: Quantum Physics

Question 1

Is the maximum kinetic energy of a photo-electron emitted from a metal in the photoelectric effect proportional to the frequency of the incident light?

Answer 1

Not unless the work function is zero. K = hf - φ so (K + φ) is proportional to frequency.

Question 2

What was it that the Compton effect illustrated?

Answer 2

Electromagnetic waves (X-rays) could act as particles (photons) when scattering off electrons.

Question 3

Which of Bohr's assumptions in creating the "Bohr atom" was revolutionary (unclassical)?

Answer 3

that angular momentum was quantized: mvr = n(h/2π); also radiates only when making transition to another orbit

Question 4

How would Bohr's theory be changed if only gravitation held the electron to the nucleus?

Question 5

Classical theory predicts that the planets can orbit the Sun quite stably. Why could not stable orbits be predicted for the atom by simply substituting the electrical attraction for the gravitational attraction? Why was there a classical crisis in describing the atom?

Question 6

Give an example of a material whose useful property depends upon a metastable state.

Question 7

What are the two basic conditions necessary for laser action?

Question 8

Planck's constant is

A) 6.6 × 10³⁴ J-s.
B) E/ $\lambda$ .
C) 4.1 × 10^-15 eV-s.
D) 6.6 × 10²⁸ MeV-s.
E) 4.1 × 10^-15 eV-min.

Question 9

The fact that $\lambda$ _mT = 2.9 × 10^-3 m-K is known as

A) Planck's law.
B) Maxwell's law.
C) Wien's law.
D) Bohr's law.
E) de Broglie's law.

Question 10

The ultraviolet catastrophe is a catastrophe because

A) Wien's law predicts an infinite intensity of radiation at large wavelengths.
B) human vision cannot detect ultraviolet light directly.
C) Wien's law predicts an infinite intensity of radiation at small wavelengths.
D) ultraviolet light will not produce electrons by the photoelectric effect.

Question 11

A blackbody is an ideal system that

A) either absorbs 100% of the light incident upon it, or emits 100% of the radiation it generates.
B) absorbs 100% of the light incident upon it, but cannot emit light of its own (i.e., a "black" body).
C) absorbs 50% of the light incident upon it, and emits 50% of the radiation it generates.
D) emits 100% of the light it generates, but cannot absorb radiation of its own.

Question 12

You may have heard it said that all objects, even ones at the temperature of our bodies, are continually emitting electromagnetic radiation. Is this true?

A) Yes, and the radiation from our bodies is mostly in the infrared region of the spectrum, and hence not detected by our eyes.
B) Yes, and this radiation is mostly in the form of radio waves, which is a common source of static often heard on an AM radio.
C) No, this is not true. If a person were emitting electromagnetic radiation, he could be seen glowing in the dark, and this is obviously not the case for most people.
D) Yes, and the radiation referred to results from the trace amounts of radioactive material that have accumulated in our bodies from the food we eat.

Question 13

Albert Einstein received the 1921 Nobel Prize for his

A) Special Theory of Relativity.
B) Theory of the Photoelectric Effect.
C) Theory of the Brownian Motion.
D) General Theory of Relativity.

Question 14

Classical theory predicted that the photocurrent, of the photoelectric effect, should be proportional to the

A) intensity of light.
B) electric field magnitude.
C) wavelength of light.
D) frequency of light.

Question 15

In the photoelectric effect, the energies of the ejected electrons

A) vary randomly.
B) are proportional to the intensity of light.
C) are proportional to the frequency of light.
D) are proportional to the speed of light.

Question 16

In a famous experiment done at the end of the 19th century, two metal electrodes were placed in an evacuated glass tube. A high voltage was applied between them. By using an appropriate metal for the cathode (e.g., sodium or potassium), it was found that a current could be made to flow when the cathode was illuminated with blue light, but no current would flow when red light was used, no matter how bright the light. Einstein was able to explain this strange phenomenon, and as a result, this experiment was considered the first experimental demonstration of

A) the particle nature of electrons.
B) the equivalency of electron and photons.
C) the wave nature of light.
D) the particle nature of light.
E) the wave nature of electrons.

Question 17

________ the CUTOFF FREQUENCY, photons do not have enough energy to dislodge photoelectrons and no photocurrent is observed.

A) Below
B) Above

Question 18

The photoelectric effect is explainable assuming

A) that light has a wave nature and a particle nature.
B) that light has a wave nature.
C) that light has a particle nature.
D) that light is an electromagnetic phenomena.

Question 19

In the photoelectric effect, the stopping potential is

A) e K_max.
B) (K_max)/e - https://d2lvgg3v3hfg70.cloudfront.net/TB9720/https://d2lvgg3v3hfg70.cloudfront.net/TB9720/.
C) K_max /e.
D) 11eea414_0aa8_cd77_97f4_af6d7fc69eef_TB9720_11.
E) K_max.

Question 20

The ratio of energy to frequency for a given photon gives

A) its work function.
B) Planck's constant.
C) its velocity.
D) its amplitude.

Question 21

Planck's constant

A) sets an upper limit to the amount of energy that can be absorbed or emitted.
B) sets a lower limit to the amount of energy that can be absorbed or emitted.
C) determines the value of the gravitational constant.
D) relates mass to energy.

Question 22

The energy of a photon depends on

A) its frequency.
B) its velocity.
C) its amplitude.

Question 23

Which color of light has the lowest energy photons?

A) yellow
B) green
C) red
D) blue
E) orange

Question 24

What is a photon?

A) a small packet of electromagnetic energy that has particle-like properties
B) an electron in an excited state
C) an electron that has been made electrically neutral
D) one form of a nucleon, one of the particles that makes up the nucleus

Question 25

A photon is a particle that

A) has a velocity in a vacuum that varies with the photon frequency.
B) cannot travel in a vacuum.
C) has zero electric field associated with it.
D) has zero electric charge.

Question 26

Which of the following is an accurate statement?

A) In vacuum, ultraviolet photons travel faster than infrared photons.
B) Infrared photons have enough energy to readily break bonds in a nucleic acid molecule like DNA.
C) Photons can have positive or negative charge.
D) An ultraviolet photon has more energy than does an infrared photon.

Question 27

In order for a photon to eject an electron from a metal's surface in the photoelectric effect, the photon's

A) momentum must be zero.
B) wavelength must be greater than a certain minimum value.
C) frequency must be greater than a certain minimum value.
D) speed must be greater than a certain minimum value.

Question 28

When the accelerating voltage in an X-ray tube is doubled, the minimum wavelength of the X-rays

A) is decreased to one-fourth the original value.
B) is decreased to one-half the original value.
C) is increased to four times the original value.
D) is increased to twice the original value.

Question 29

When monochromatic X-rays are scattered by a material, the wavelength of the scattered radiation does not depend upon

A) the scattering angle.
B) the type of atom.
C) incident wavelength.
D) mass of the interacting particle.

Question 30

The Compton effect importantly demonstrated which property of electromagnetic radiation?

A) momenta
B) its wavelength
C) particle nature
D) energy content

Question 31

In the Compton effect, as the scattering angle increases, the frequency of the X-rays scattered at that angle

A) varies randomly.
B) decreases.
C) does not change.
D) increases.

Question 32

In a Compton scattering experiment, what scattering angle produces the greatest change in wavelength?

A) 45.°
B) 180.°
C) zero degrees
D) 90.°
E) 270.°

Question 33

Bound electrons have

A) infinite energy.
B) zero energy.
C) imaginary energy.
D) positive energy.
E) negative energy.

Question 34

Photons are emitted when a bound electron jumps up to a(n) ________ energy state.

A) zero
B) higher
C) lower
D) infinite

Question 35

Light from a gas discharge tube gives a (an) ________ spectrum.

A) emission
B) blackbody
C) continuous
D) absorption

Question 36

Which hydrogen spectral series falls in the visible region?

A) Lyman
B) Paschen
C) Balmer
D) Brackett

Question 37

The energy difference between adjacent orbit radii in a hydrogen atom

A) remains constant for all values of n.
B) increases with increasing values of n.
C) varies randomly with increasing values of n.
D) decreases with increasing values of n.

Question 38

When an electron jumps from an orbit where n = 4 to one where n = 3

A) two photons are emitted.
B) a photon is emitted.
C) a photon is absorbed.
D) two photons are absorbed.

Question 39

In order for the atoms in a neon discharge tube (or a neon beer sign) to emit their characteristic orange light, it is necessary that

A) the atoms be continually replaced with fresh atoms, because the energy of the atoms tends to be used up with continued excitation, resulting in dimmer and dimmer light.
B) electrons first be given energy to raise them from their ground state to an excited state.
C) there be no unoccupied energy levels in each atom.
D) each atom carry a net electric charge.

Question 40

In the Bohr theory the orbital radius depends upon the principal quantum number in what way?

A) n³
B) n
C) 1/n
D) n²
E) 1/n²

Question 41

How many of the infinite number of Balmer spectrum lines are in the visible spectrum range?

A) none
B) 2
C) 4
D) 6
E) infinite

Question 42

The word LASER is an acronym for

A) Light Amplification by the Stimulated Emission of Radiation.
B) Light Altered Spectra of Energy Radiated.
C) Light Absorbed States of Energetic Resonance.
D) LAtent Source of Enhanced Radiation.

Question 43

In a He-Ne laser, the actual emission line at 632.8 nm comes from a jump down in what atom(s)?

A) helium
B) oxygen
C) hydrogen
D) neon
E) helium and neon

Question 44

The compact disc stores information by means of

A) Compton scattering.
B) stimulated absorption.
C) pits and lands.
D) the photoelectric effect.
E) holography.

Question 45

When a hologram is illuminated with a beam of coherent light, it produces

A) both a real and a virtual image.
B) only a virtual image of the object.
C) only a real image of the object.

Question 46

The human eye can just detect green light of wavelength 500. nm, which arrives at the retina at the rate of 2 × 10^-18 W. How many photons arrive each second?

Question 47

The graph shown in Figure 27-1 is a plot based on student data from their testing of a
photoelectric material.

(a) Determine the cutoff frequency.
(b) Determine the work function.

Question 48

What is the radius of the electron orbit in a singly ionized helium ion?

Question 49

What is the ionization energy for a doubly ionized lithium ion (Z = 3)?

Question 50

What is the energy, in eV, of the n = 3 state in hydrogen?

Question 51

Bohr's atomic theory predicted energy levels for hydrogen of E_n = -(2 π²k²e⁴m) about a bare nucleus of atomic number Z, how do you expect Z to be incorporated into the E_n formula and why?

Question 52

If sunlight peaks at 0.55 ?m wavelength, this infers a surface temperature of the sun of how many thousand degrees Kelvin?

A) 2.5
B) 9.5
C) 5.3
D) 15.
E) 25.

Question 53

How much energy is carried by a photon of wavelength 660. nm?

A) 4.78 × 10^-19 eV
B) 6.63 × 10^-34 J
C) 5.39 eV
D) 3.01 × 10^-19 J
E) 1.46 × 10^-48 J

Question 54

What change in wavelength is expected when X-rays are scattered at 90°?

A) 3.75 × 10^-3 nm
B) 4.84 × 10^-3 nm
C) 2.42 × 10^-3 nm
D) 1.18 × 10^-3 nm
E) no change at this angle

Question 55

The energy required to ionize a hydrogen atom from the ground state is

A) 3.4 eV.
B) 6.8 eV.
C) 13.6 eV.
D) infinite.
E) 27.2 eV.

Question 56

Consider an atom with four accessible energy levels. What is the maximum number of different wavelengths that could be emitted by such an atom?

A) 5
B) 8
C) 4
D) 6
E) 7

Question 57

In state n = 1, the energy of the hydrogen atom is -13.58 eV. What is its energy in state n = 2?

A) -1.51 eV
B) -6.79 eV
C) -4.53 eV
D) -5.89 eV
E) -3.40 eV

Question 58

What is the ionization energy of singly ionized helium?

A) 54.4 eV
B) 27.2 eV
C) 6.80 eV
D) 13.6 eV
E) 36.4 eV