Photoelectric Effect Flashcards

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1
Q

Describe the photoelectric effect

A

Photoelectrons are emitted from the surface of a metal after light above a certain frequency is shone on it. This certain frequency is different for different metals.
Photo electrons are emitted because electrons near the surface of the metal absorb a photon and gain enough energy to leave the surface.

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2
Q

Photon energy equation

A

E=hf=ø+Ek(max)

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3
Q

What is the work function

A

The minimum energy required for electrons to be emitted

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4
Q

Threshold frequency

A

The minimum frequency of light required to emit photo electrons

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5
Q

What is an electron volt

A

Unit of energy, usually used to express small energies

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6
Q

What is an electron volt equal to

A

The kinetic energy of an electron accelerated across a potential difference of 1V or 1.6x10^-19

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7
Q

Convert joules to electron volts

A

Divide by 1.6x10^-19

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8
Q

Electron volts to joules

A

Multiply by 1.6x10^-19

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9
Q

The photoelectric effect as evidence of the particle nature of EM radiation

A

1)wave theory would suggest ANY frequency should cause emission, which is wrong
2)the photoelectric effect is immediate
3)increasing the intensity has no effect of the speed of emission

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10
Q

Why light is a particle

A

1)one photon interacts with one single electron and all it’s energy is transferred to it.
2)the transfer of energy is immediate
3)intensity is equal to the number of photons released per second
4)all electrons will receive the same amount of energy from a photon of light, however deeper electrons loose energy through collisions when leaving the metal

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11
Q

What happens when an electron gains a certain amount of energy

A

They move up an energy level (excitation)

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12
Q

What happens after excitation

A

The electron will quickly return to its original level and release energy in the form of a photon

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13
Q

How can you get a line spectrum

A

Passing light from a fluorescent tube through a diffraction grating OR prism

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14
Q

What does each line in the light spectrum represent

A

A different wavelength of light

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15
Q

What is the evidence to show electron in atoms can only transition between discrete energy levels

A

The light spectrum is not continuous but contains only discrete wavelengths, photons energies must correspond to the wavelengths

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16
Q

What is the difference between two energy levels equal to

A

A specific photon energy emitted

17
Q

what is quantisation of energy

A

the idea that energy is emitted in discrete packets, photons. each photon has energy related to their frequency