Photons & Electrons (Finals)(2 Nov)

λ ~

wavelength (m)

c ~

speed of light (m.s⁻¹)

which color has the highest frequency

violet/purple

what does a lesser frequency mean?

lower photon energy (E = hf) and a longer wavelength

what has no effect on electron speed (or maximum kinetic energy)?

light intensity (intensity only affects the number of photoelectrons emitted per second, not their speed)

what phrase must be remembered in photoelectric explanations?

"per unit time" (or "per second") when discussing emission rate and current

what is the same thing as brightnessmore photoelectrons are ejected per second, photoelectric current increases, but maximum kinetic energy ($E_k$) and energy per photon remain the same

intensity

what does an increase in brightness mean?

more photoelectrons are ehected per second with Ek and the current increases and energy is the same

what is f directly proportional to and what is Wo directly proportional to

f ∝ x

Wo ∝ fo

how does the visible light frequency work (ROYGBIV)?

increases from Red to Violet/Purple (while wavelength decreases)

what do variables in E = Wo + Ek(max)

E - light

Wo - metal

Ek - ½ mv∝

what mass value to use if dealing with electron Ek or v?

mass of an electron (me =…)

why do the leaves of an electroscope diverge (lift)?

• electrons are ejected from the object, leaving behind positive charges on the leaves so they repel each ot

effect of increasing light intensity on an electroscope?

more photons strike the metal surface per second, emitting more electrons, causing the leaves to diverge more rapidly/further

what to remember about electrolytic cells

• non-spontaneous redox reaction (E⦵ celll < 0)

• requires an external DC power source

• electrical energy is converted into chemical energy

main uses/applications of electrolytic cells

• Decomposition of copper(II) chloride

• Electroplating

• Electrorefining

• Chlor-alkali industry (electrolysis of concentrated sodium chloride / brine)