Honors Chemistry
Unit 3 - Electrons
Lesson 2 – Photoelectric Effect & Wave
Formulas
Book Section: 4-1
Do Now: Prepare for Quiz 3-1.
Objective: SWBAT use wave formulas to
solve problems w/ frequency & wavelength.
Agenda: Quiz, Lesson, Videos, Element of
the Day
Electromagnetic Radiation

All
electromagnetic
radiation travels at
the same velocity:
the speed of light
(c).

c = 3.00 x 108 m/s
c  
Practice

The yellow light given off by a sodium vapor lamp
used for public lighting has a wavelength of 589 nm.
What is the frequency of this radiation?
Practice

The yellow light given off by a sodium vapor lamp
used for public lighting has a wavelength of 589 nm.
What is the frequency of this radiation?

5.09 x 1014 s-1 (or Hz)
Photoelectric Effect



Problem with light as a
wave – does not explain
the photoelectric
effect.
Albert Einstein – won
Nobel Prize for showing
that the color of light
determines energy, not
intensity.
VIDEO: Photoelectric
Effect
Photoelectric Effect




The only way to rationalize that the color matters
more than intensity was to think of light as a
“packet,” or particle of light called a photon.
Blue photons had more energy than red photons.
You can shoot a machine gun against a brick
wall, but the wall won’t fall. You need a wrecking
ball. Lots of red photons won’t generate a
current, but a few blue ones will.
Light behaves as both a wave and as a
particle…… strange…
HW 3-2: #24-25

This Week:



Thursday: The Mole & Energy of Light (4-1), Quiz
3-2
Friday: The Bohr Model of the Atom (4-1),
Quiz 3-3
Likely Unit 3 Test Date: Tuesday, October 19