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Physics > Dual Nature Of Matter And Radiation > Flashcards

Dual Nature Of Matter And Radiation Flashcards

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1
Q

What is electromagnetic radiation?

A

Electromagnetic radiation consists of mutually perpendicular oscillating electric and magnetic fields, both being perpendicular to the direction in which the wave and energy are travelling.

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2
Q

What are the characteristics of a wave?

A

Characteristics of a wave include frequency, wavelength, amplitude, and speed.

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3
Q

Define frequency and wave number associated with a wave.

A

Frequency is the number of oscillations per unit time, while wave number is the number of wavelengths per unit distance.

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4
Q

How do we define momentum of a particle?

A

Momentum of a particle is defined as the product of its mass and velocity (p = mv).

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5
Q

What is the concept of quantization of energy?

A

Quantization of energy refers to the idea that energy is emitted in discrete packets or quanta.

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6
Q

Who first proposed the idea of quantization of energy?

A

Planck first proposed the idea of quantization of energy.

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7
Q

What is the relationship described by Planck’s model for energy emission?

A

Energy is emitted in packets, and at higher frequencies, the energy of a packet is larger (E = nhν).

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8
Q

What phenomenon did Heinrich Hertz discover in 1887?

A

Heinrich Hertz discovered photoelectric emission.

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9
Q

What is the photoelectric effect?

A

The photoelectric effect is the emission of electrons from a metal surface when radiation of appropriate frequency is incident on it.

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10
Q

What is required for the photoelectric effect to occur in metals like zinc and magnesium?

A

Ultraviolet radiation is necessary for the photoelectric effect to occur in metals like zinc and magnesium.

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11
Q

What are the two ways electrical energy can be obtained from light?

A
  • Photo-emissive effect
  • Photo-voltaic effect
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12
Q

What is the typical experimental setup for the photoelectric effect?

A

An evacuated glass tube with a quartz window containing a photosensitive metal plate (emitter) and a collector plate.

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13
Q

What happens when the anode potential is positive in the photoelectric effect setup?

A

It accelerates the electrons.

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14
Q

What is the role of the stopping potential in the photoelectric effect?

A

The stopping potential indicates the maximum energy needed to prevent photoelectrons from reaching the collector.

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15
Q

What is the work function of a metal?

A

The minimum amount of energy required to remove an electron from the surface of the metal.

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16
Q

True or False: The maximum kinetic energy of emitted photoelectrons depends on the intensity of the incident radiation.

A

False.

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17
Q

What does the photoelectric equation relate?

A

It relates the energy of incident light to the kinetic energy of emitted electrons.

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18
Q

What is the value of Planck’s constant?

A

6.626 × 10^-34 J s.

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19
Q

Fill in the blank: The equation E = hν is known as _______.

A

Einstein’s relation.

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20
Q

What phenomenon cannot be explained by wave theory regarding the photoelectric effect?

A

The instantaneous emission of electrons upon incidence of light.

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21
Q

What is the threshold frequency in the context of the photoelectric effect?

A

The minimum frequency of incident radiation required to emit photoelectrons from a metal surface.

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22
Q

What is the relationship between maximum kinetic energy and incident frequency?

A

Maximum kinetic energy increases with increasing incident frequency.

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23
Q

What is the significance of the stopping potential V0?

A

It indicates the point at which the photocurrent becomes zero despite the incident radiation.

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24
Q

How does the saturation current depend on intensity of incident radiation?

A

The saturation current increases proportionally with the intensity of the incident radiation.

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25
Q

What is Planck’s constant and its value?

A

Planck’s constant is a fundamental constant used in quantum mechanics, defined as h = 6.626 × 10^-34 J s.

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26
Q

What does Einstein’s relation E = hν represent?

A

It represents the relationship between energy (E) and frequency (ν) of electromagnetic radiation.

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27
Q

What does Einstein’s relation indicate about energy and frequency?

A

Energy is directly proportional to frequency and inversely proportional to wavelength.

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28
Q

Fill in the blank: High frequency radiation means _______ radiation.

A

high energy

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29
Q

What are the energy values for various photon energies given in the example?

A

10^-12 J, 10^-15 J, 10^-18 J, 10^-21 J, 10^-24 J.

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30
Q

What is the formula for energy of electromagnetic radiation?

A

E = hν.

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31
Q

What is the threshold frequency for photoemission?

A

The minimum frequency (ν₀) required to eject electrons from a metal surface.

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32
Q

True or False: Electrons will be emitted if the energy gained by them is less than the work function.

A

False.

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33
Q

What does the equation KEmax = hν - φ₀ represent?

A

It describes the maximum kinetic energy of emitted electrons in the photoelectric effect.

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34
Q

Fill in the blank: Photocurrent depends on the intensity of incident radiation through the number of _______ emitted.

A

photoelectrons

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35
Q

What happens to photocurrent when the intensity of incident radiation increases?

A

The number of emitted photoelectrons increases, leading to a higher photocurrent.

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36
Q

What is the significance of the stopping potential (V₀)?

A

It indicates the potential required to stop the most energetic emitted electrons from reaching the collector.

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37
Q

What relationship does V₀ have with incident frequency (ν)?

A

V₀ varies linearly with incident frequency.

38
Q

Fill in the blank: The energy of a photon is given by _______.

A

hν

39
Q

What did Einstein argue about the interaction of photons with electrons?

A

A photon gives all its energy to an electron upon collision, and the photon ceases to exist.

40
Q

What is the formula to calculate the number of photons incident per second?

A

N = Power / Energy of a single photon.

41
Q

How does the energy of emitted electrons vary?

A

Electrons have different kinetic energies due to varying depths of ejection and collisions.

42
Q

What is the relationship between wavelength and energy for photons?

A

Wavelength (in Å) × energy (in eV) ≈ 12500.

43
Q

What does the Compton shift relate to?

A

It relates the change in wavelength of photons due to scattering with electrons.

44
Q

True or False: Photons can be absorbed or created during collisions.

A

True.

45
Q

What is the relationship between intensity and electron energy in the photoelectric effect?

A

Intensity affects the number of emitted electrons but not their energy.

46
Q

What is a key conclusion from the experiments on the photoelectric effect?

A

Light behaves as packets of energy called quanta.

47
Q

Fill in the blank: A photon of low frequency light will not have sufficient energy to _______ an electron.

A

release

48
Q

What is the effect of increasing the frequency of incident light?

A

It increases the maximum kinetic energy of the emitted electrons.

49
Q

What did Compton demonstrate about photons?

A

Photons have associated momentum along with the energy they carry

This was established through experiments showing that photons interact with matter.

50
Q

What is the rest mass of a photon?

A

Zero

Photons are massless particles and always move at the speed of light.

51
Q

In photon-particle collisions, what quantities are conserved?

A

Energy and momentum

However, the number of photons is not conserved as photons can be absorbed or created.

52
Q

What is Compton shift?

A

The change in wavelength of scattered photons, denoted as Δλ

It depends on the scattering angle during photon-electron collisions.

53
Q

What experiments demonstrate the particle nature of radiation?

A

Black body radiation and photoelectric effect

These phenomena can only be explained by considering radiation as consisting of photons.

54
Q

What does wave-particle duality imply?

A

Both wave and particle characteristics are necessary to describe electromagnetic radiation

This concept applies to both light and the entire electromagnetic spectrum.

55
Q

What is a photocell?

A

A device that converts light energy into electrical energy

It operates using the photoelectric effect and is used in various applications like light meters.

56
Q

How does a photocell work?

A

When suitable light falls on the cathode, photoelectrons are emitted and create a photocurrent

This current can be measured and used to trigger other devices.

57
Q

What did de Broglie hypothesize about matter?

A

Matter may also possess dual nature, exhibiting both wave and particle properties

This was based on the observed symmetry in nature.

58
Q

What is the de Broglie wavelength formula?

A

λ = h/p

Where h is Planck’s constant and p is momentum.

59
Q

What confirms the wave nature of electrons?

A

The Davisson and Germer experiment

It demonstrated electron diffraction patterns, similar to wave interference.

60
Q

What is the significance of the Davisson and Germer experiment?

A

It substantiated de Broglie’s hypothesis of wave-particle duality

The experiment showed that electrons exhibit wave-like behavior.

61
Q

What is the relation between kinetic energy and de Broglie wavelength for a charged particle?

A

λ = h / √(2mEK)

Where EK is the kinetic energy and m is the mass of the particle.

62
Q

True or False: The de Broglie wavelength of larger objects like cars or humans is significant.

A

False

The calculated wavelengths are extremely small and not observable.

63
Q

Fill in the blank: The phenomenon of light exhibiting both wave and particle characteristics is known as _______.

A

wave-particle duality

64
Q

What defines the momentum of a photon?

A

p = E/c

This relationship is valid for massless particles traveling at the speed of light.

65
Q

What is the formula for de Broglie wavelength?

A

λ = h/p

66
Q

What is the value of Planck’s constant h?

A

6.63 × 10^-34 J s

67
Q

What is the de Broglie wavelength of a car moving with a momentum of 20000 kg m/s?

A

3.32 × 10^-38 m

68
Q

What phenomenon describes the wave-like nature of material particles?

A

Wave-particle duality of matter

69
Q

What are the classical terms used to describe waves?

A
  • Frequency (ω) * Wave number (k)
70
Q

Why are the wavelengths associated with macroscopic particles negligible?

A

They are negligible compared to the size of the moving objects and the widths of their paths.

71
Q

What is the significance of the de Broglie wavelength for an electron passing through a small aperture?

A

It is comparable to the size of the hole.

72
Q

What is the de Broglie wavelength of an electron with kinetic energy of 100 eV?

A

1.228 Å

73
Q

What effect does the wavelength of the characterizing probe have on the resolution of a microscope?

A

The shorter the wavelength, the better the resolution.

74
Q

What is thermionic emission?

A

The process of emitting electrons by heating a material to high temperatures (~2000 ºC).

75
Q

What is field emission?

A

The process of emitting electrons by applying strong electric fields (~10^6 V/m) at the surface of a metal tip.

76
Q

What is photo-electron emission?

A

The process of emitting electrons by shining suitable frequency radiation (ultraviolet or visible) on a metal surface.

77
Q

What is the primary advantage of electron microscopes over optical microscopes?

A

Higher resolution due to shorter wavelengths associated with electrons.

78
Q

Who developed the first electron microscope and when?

A

Herald Ruska in 1929.

79
Q

What is the relationship between stopping potential and incident wavelength in the photoelectric effect?

A

The stopping potential is inversely linear with the incident wavelength.

80
Q

What happens to the extra energy of incident radiation in the photoelectric effect when intensity increases?

A

It does not change the maximum kinetic energy of the electrons.

81
Q

What is the work function in the context of photoelectric effect?

A

The minimum energy needed to remove an electron from a material.

82
Q

What is the stopping potential if the photocurrent vanishes?

A

It is the maximum retarding potential that prevents photoelectrons from reaching the anode.

83
Q

What is the threshold wavelength for tungsten?

A

2.76 × 10^-5 cm

84
Q

What is the energy of a photon with a frequency of 5×10^14 Hz?

A

3.315 × 10^-19 J (or 2.071 eV)

85
Q

What is the significance of the Davisson and Germer experiment?

A

It demonstrated the wave nature of electrons through diffraction.

86
Q

Fill in the blank: The de Broglie wavelength of an electron is _______.

A

λ = h/p

87
Q

True or False: Electrons can behave as waves.

A

True

88
Q

What is the typical resolution of electron microscopes compared to optical microscopes?

A

Several hundred times higher.

89
Q

What happens to photoelectrons when radiation of wavelength greater than the threshold wavelength is incident on a metal surface?

A

No photoelectrons are emitted.

90
Q

What is the maximum kinetic energy of photoelectrons when ultraviolet radiation of wavelength 1.80 × 10^-5 cm is incident on tungsten?

A

2.40 eV

91
Q

What is the expected behavior of an electron at rest in relation to de Broglie wavelength?

A

An electron at rest does not have an associated de Broglie wavelength.

92
Q

What is the significance of the wavelength being comparable to atomic dimensions in electron diffraction?

A

It allows for the study of atomic structures.

Physics (3 decks)

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