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Physics > 3. Photons and Lasers > Flashcards

3. Photons and Lasers Flashcards

1
Q

Photon

A

The smallest possible amount of light energy

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2
Q

Absorption

A

When electrons on lower energy levels receive photons of an energy that matches the change in the energy levels

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3
Q

Emission

A

When the electron releases a photon back into space

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4
Q

Ionisation

A

When an electron is moved up or down an energy level depending on how much energy it has

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5
Q

Ionisation energy

A

The energy needed to knock an electron out of its energy level

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6
Q

Stimulated emission

A

The emission of a photon from an excited atom which is triggered by an incident photon of energy equal to the gap between the excited state and lower energy level.

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7
Q

Population inversion

A

When more electrons (more populated) are on a higher energy level than the one below it

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8
Q

Pumping

A

When an electron receives a photon of the same energy difference and then moves up to a higher energy level

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9
Q

Photoelectric effect

A

The release of electrons from the surface of a metal when electromagnetic radiation is incident on its surface. This then reduced the overall charge of the object.

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10
Q

Work function (WF)

A

The minimum amount of energy needed by an electron to allow it to move off the surface of a metal

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11
Q

Max kinetic energy of electrons

A

Ekmax = hf - WF

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12
Q

Threshold frequency

A

The minimum frequency for which photoelectrons are emitted

The Ekmax would be 0

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13
Q

Electron volt (eV)

A

The amount of kinetic energy an electron will receive after being accelerated through 1V

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14
Q

Stopping potential

A

The amount of volts needed to show the ammeter reading as 0

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15
Q

V stop equation

A

Ekmax = e x Vstop

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16
Q

Change in energy equation

A

E2 - E1

17
Q

Photon energy equation

A

E = hf (- WF)

18
Q

Alternate photon energy equation

A

E = hc / wavelength (-WF)

19
Q

What are the quantities gathered from a Graph of KE against Frequency

A

Gradient = Plancks constant

Y-intercept = The work function x -1

20
Q

Milikans experiment

A

The experiment to find the Vstop of an electron by using a circuit.
Measured the frequency of light and also the KE of the photons that are emitted off the metal surface.

21
Q

Wave particle duality

A

The ability of waves to behave as particles and as waves

22
Q

Conductor

A

A material through which electrons can flow easily

23
Q

Insulator

A

A material in which electrons cannot flow easily

24
Q

Electroscope

A

A device used to detect the existence of electrical charge

25
Q

Absorption spectra

A

A rainbow spectrum with black lines, this shows the certain frequencies of light radiated.

26
Q

Emission spectra

A

A black background with coloured lines, it represents the electrons moving through different energy levels. They loose energy as they produce a photon which then creates emission lines.

27
Q

Monochromatic

A

Photons or waves of a single wavelength

28
Q

Coherence between incident and emitted photons

A

The relationship between the incident photon and the emitted photon is coherent as they are the dame frequency and in phase

29
Q

Gas laser pros and cons

A

Large
Expensive
Inefficient
However, used when the laser needs to produce a specific wavelength

30
Q

Semiconductor / laser diodes pros and cons

A

Small
Cheap
Very Efficient
Most common and used for eye surgery / image scanning

31
Q

Metastable

A

When an energy level in a laser is almost stable to hold electrons without spontaneous emission

32
Q

Ionisation energy

A

The energy needed for an electron to escape the atom, the energy needed is just above the highest energy level
(In an exam question if it asks for the ionisation energy then write the highest energy level)

33
Q

Light Amplification

A

The stimulation causes double the amount of photons to be emitted. (exponentially increases)

34
Q

Different types of lasers

A

2 level energy system
3 level
4 level

35
Q

Excitation

A

When an electron gains more energy and moves to a higher energy level

36
Q

Spontaneous emission

A

When an electron drops to a lower metastable level and emits a photon

37
Q

What is the photo electric effect

A

When photons are incident upon a metal surface with the same wavelength as the electrons. this causes the electrons to eject from the surface

38
Q

What is the de broglie wavelength

A

wave length = h / momentum
we use this equation as the size of the gap needed to diffract them cannot be achieved

39
Q

What is the radiation pressure

A

The change in momentum of electromagnetic radiation, this then causes pressure to be exerted upon a surface

Physics (17 decks)

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