Chapter 4: Particles of Light Flashcards

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1
Q

What is the photoelectric effect?

A

The emission of photoelectrons from a metal surface exposed to e-m radiation of a high enough frequency

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2
Q

What is a photon?

A

A quantum of light which is a small indivisible packet of energy

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3
Q

What is frequency proportional to for photons?

A

The energy of the photons

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4
Q

What is intensity proportional to for photons?

A

The number of photons arriving per second per unit area

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5
Q

What is the threshold frequency?

A

The minimum frequency of light (photons) required for photoelectrons to be emitted from a metal surface through the photoelectric effect

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6
Q

What is the work function?

A

The minimum energy required to remove an electron from a metal’s surface through the photoelectric effect

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7
Q

What is Einstein’s photoelectric equation?

A

E= hf= Φ + Ekmax
E= energy
h= Planck’s constant
f= frequency of the radiation (Hz)
Φ= work function of material (J)
Ekmax= max. kinetic energy of photoelectrons (J)

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8
Q

What is the stopping potential?

A

The minimum negative voltage applied to the anode to stop the photocurrent.
The maximum kinetic energy of the electrons equal the stopping voltage, when measured in electron volt.

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9
Q

How is stopping potential calculated?

A

eVstop= Ekmax

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10
Q

What is the equation for de Broglie wavelength?

A

λ= h/p
λ= de Broglie wavelength (m)
h= Planck’s constant
p= momentum (mv) (kgms-1)

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11
Q

What is electron diffraction and what is it evidence for?

A

The spreading of electrons as they pass through a gap similar to the magnitude of their de Broglie wavelength to produce a diffraction image.
It is evidence of the wave-like properties of particles

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12
Q

What happens during electron diffraction?

A

-Beam of electrons fired from electron gun (cathode ray gun) through thin graphite screen.
-Arranged in lattice and acts like a diffraction grating, electrons diffract and interfere to form a single pattern of diffraction rings.

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13
Q

How does de Broglie wavelength change as momentum increases?

A

As momentum of electrons increases, de Broglie wavelength decreases and so the electrons diffract less, causing smaller spaced rings.

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14
Q

What is wave-particle duality?

A

The idea that matter and radiation can be described best by sometimes using a wave model and sometimes using a particle model

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15
Q

What are some examples for wave-like properties and particle-like properties?

A

Photoelectric effect: particulate nature
Electron diffraction: wave nature
Excitation and de-excitation: particulate nature
Young’s double slit: wave nature

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