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3F: Sugery > Dual Nature Of Radiation > Flashcards

Dual Nature Of Radiation Flashcards

1
Q

Plancks equation

A

E=nhf

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2
Q

Einstein and light

A

Particle and wave

Photoelectric effect

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3
Q

Compton effect

A

Light has momentum

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4
Q

A disturbance or change that propagates through the available space or medium

A

Wave

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5
Q

Transverse waves

A

Oscillation perpendicular to the direction of propagation

  • oscillation-up or down
  • propagation-horizontal

Example: stone dropped into a pond

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6
Q

The Doppler shift

A

A stationary point srouce emitting spherical waves

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7
Q

A point source moving to the right while emitting spherical waves

A

The wavelength in front of the point source is shifted to a shorter wavelength (a blue shift), while the wavelgnth behind the point source are shifted to a longer wavelength (a red shift)

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8
Q

A point source moving to the right while emitting spherical waves: the distance between the wavefronts (the wavelgnth) of the emitting light

A

Is shorter to the right or in front of the moving point source

  • therefore an observer looking at the source, the incident light shifted is shifted toward a shorter wavelgnth (a blue shift) when the source is traveling (quite fast) toward the observer
  • the distance between the wavefronts behind (to the left of) the moving point source is longer
  • therefore an observer looking at the srouce, the light shifted toward a longer wavelgnth (a red shift) when the source is traveling (quite fast) away from the observer. This is call them Doppler shift.
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9
Q

The Doppler shift in radar waves

A

Used in the speed of detection of cars, trucks, and even clouds

The Doppler shift of laser light has been used to measure the velocity of blood cells flowing through retinal blood vessles

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10
Q

Blackbody radiation

A

-a material that absorbs most of the incident light
-according to the law of conservation (for the incident light)
The absorptance + the reflectance + the transmittance=1

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11
Q

Ideal black body

A
  • the electromagnetic radiation from a hot object is called thermal radiation
  • the pectoral distribution of therma radiation is largely a function of the temp of the source
  • to understand the emission properties of blackbody, consider a ball suspended by an insulated string in a closed cavity
  • when the cavity is heated to a certain temp, the walls emit electromagnetic radiation. This radiation is incident on the suspended ball, which in turn absorbs and re-radiates
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12
Q

Kirchhoff’s law

A

Shows the amount of emittance is directly proportional to the absorptance A

E1/A1=E2/A2
E-the radiation emitted by the ball
A1=absorptance of the ball

A ball that doe not absorb much (small A) also does not emit much (small E). A ball that absorbs a lot (large A) also emits a lot (Large E)

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13
Q

In an absorbing material, a cavity with a small opening approaches an ideal blackbody. When light is incident on the hole, it passes into the cavity and reflects back and forth from the interior cavity walls until it is absorbed.

A

Very little light comes back out of the small opening. Hence, the opening appears to be an ideal black spot
-the pupil of your eye appears black for similar reasons

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14
Q

Blackbody radiator

A

Thermal radiation
Heat the blackbody
When it is 2000K=red
When it is increased, gets brighter, but then you realize that its not red anymore, it’s orange.
When you increase it to even more orange, it looks more blue and brighter.

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15
Q

Blackbody radiator and colro temprerature

A

-when you heat the metal more, the energy increases and you see a shift, it moves towards blue and shorter wavelgnth (higher Frequnciy when it gets hotter)

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16
Q

Where does blackbody radiator look mroe blue

A

9000-10000K

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17
Q

Sun spectrum, in blackbody spectrum

A

5,800K

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18
Q

Candle in black body radiation

A

1,800K

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19
Q

Two characteristics of blackbody radiation

A
  1. Peak wavelgnth is inversely propeotional to the temperature. Increase temperature, shorter wavelength. This is called Wien’s displacement law.
  2. Another characteristic of blackbody radiation is- that the total irradiance I(t) is directly proportional to the fourth power of the temperature. This is known as the Stefan-boltzman law. The strong temperature dependence results in a dramatic increase in irradiance as T(k) increases
20
Q

Because of the two laws of blackbody radiator

A

Care must be taken in judging apparent colors

  • a dim light may have a peak wavelength in the red, when you increase the current in a filament, the filament gets hotter and emits more light
  • however, the peak wavelength emitted also shifts up, so the incidenct of light is bluer than before, and as result an illuminated object may appear bluer
21
Q

The blackbody spectrum is analyzed by examining the standing wave modes set up in the cavity. First break down at atomic level

A
  • the classical analysis correctly fits the low frequency part of the blackbody spectrum, but goes haywire at the higher frequencies
  • as a function of increasing frequency, the experimental curve peaks and turns down, while the classical prediction continues to grow
  • this is know as the UV catastrophe of classical electromagnetic wave theory
22
Q

Photoelectric effect

A

Photoelectric effect

  • in metals, the electrons in the outer shells are lookselt bound to the atoms, and they freely move with the metal surface but cannot leave the metal surface, called free electrons
  • these free electrons can be emitted from the metals, if they have sufficiency energy to overcome the attractive pull of metal surface
  • this phenomena of emission of electrons fro the surface of a metals is called electron emission
23
Q

Photoelectrons

A

It is the phenomenon of emissions of electrons from the surface of metal when light radiations of suitable freiwncy fall on it, the emitted electron are now called photoelectrons

24
Q

The minimum energy required by an electron to escape from the metal surface is called the _____ of the metal

A

Work function

25
Q

In the photoelectric effect, electromagnetic radiation of _____ incident on a metal results in the ejection of electors

A

High frequency

26
Q

Classical electromagnetic theory predicts that

A
  • the metal wit hthe electrons with a time lag (delay or sunbathe)
  • the effect should be frequency-independent, and
  • the maximum kinetic energy of the ejected electrons should be dependent on the irradiance of light
27
Q

Second breakdown in classical electromagnetic wave theory in blackbody radiator

A
  • when the frequency is high enough the electrons are ejected immediately (no time lag)
  • the effect is very frequency dependent (only high frequency)
  • the maximum kinetic energy of the ejected electrons is independent of the irradiance
28
Q

Both of the breakdowns (blackbody reaction and the photoelectric effect) were solved by

A

The quantum theory of light

29
Q

Quantum theory

A

Correctly describes electromagnetic radiation interacts at the atomic level,

30
Q

Electromagnetic wave theory

A

as well as encompassing and including the classical electromagnetic wave theory at the macroscopic level

31
Q

A central feature of the quantum theory of light is that the energy carried by the electromagnetic radiation is not continueous, but comes in packets called

A

Photons

32
Q

Photons: energy and momentum

A

-the packets of energy are called “light quantum” assocaited with particles called “photons.” Photons confirm the particle nature of lights

Energy of photon is give by E=hf=Hx/WL

33
Q

Moving photons with mass

A

E=hf

Where E is the photon energy, m is the mass equivalent, and c is the speed of light . The result is

M=(hf)/c^2

Since a photon has a mass equivalent, it caries memomtum as well as energy

34
Q

Besides mememtnum, a photon also carries _______. It is the photon spin that is responsible for the polarization properties of light

A

Angular momentum

35
Q

Characteristics properties of photons

A
  • as the interaction of radiation with matter, radiation behaves like particles called photons
  • photoson are always moving with the speed of light in vacuum. Attempts to top photon results in its absorption
  • phitoson travel in straight line
  • photons are not electrical charged but are emitted and absorbed BYU electrically charged particles
  • photons have zero rest mass, but photons never occur at rest
  • the energy of the photon does not change when it travels from one medium to another. It is because that the energy of photon depends on frequency
  • wavelength of photon changes in different media
  • photons are not deflected by the electric or magnetic fields. Photons are electrically neutral
  • in photon, particle collisions, the energy and the momentum are conserved. However, the number of photons may not be conserved in the collision
36
Q

Bohr atom model

A
  • according to the Bohr model of the atom, the electrons that orbit the atomic nucleus exist only in discrete energy levels
  • an electron can jump to a slower energy level by emitting photon. Similarly, an electron can jump to a higher level by absorbing a photon
37
Q

Ground state in the Bohr model

A

The lowest energy level

38
Q

Stable state in Bohr model

A

In the absence of incident radiation, the groun state is the stable state of the atom

39
Q

Excited state int he Bohr model

A

Higher states, not stable

40
Q

Spontaneous emission of photon

A

An electron typically stays in an excited starte for less than 10^(-8) s and then jumps to a lower level emitting a photon in the process

The energy of the smithed photon equals the difference in the energy levels. An electron can jump to a higher energy level by absorbing a photon that carries energy equal to that of the jump

41
Q

Lyman series

A

Those that end in the ground state

42
Q

Balmer series

A

Those that end in the first excited state E1

43
Q

Pashcen series

A

Those that end in the second excited state E2

44
Q

Ultraviolet photons

A

The jumpers to the ground state are all large, and these give UV photons

45
Q

The visible wavelengths from from the ____series

A

Balmer

46
Q

The pashen series has smaller energy jumps and gives _______ photons

A

Infrared

3F: Sugery (5 decks)

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