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WAVES
PROBLEM 1- CONCEPTUAL QUESTIONS
Red light falls around 700 nm green light falls around
500 nm. Which color is highest in frequency? Which
color is highest in energy ?
PROBLEM 2- SYNTHESIS PROBLEM
2) Synthesis problem: Given the electromagnetic spectrum, which
is more damaging to the skin, UV or microwaves? Why ? Note,
throw out possible ideas that could create this. Brainstorm ideas and submit them. You won’t
be penalized for being wrong.
PROBLEMS 3- Synthesis Problem:
3) UV light is subdivided into classifications UVAI (longest wave), UVAII, UVB and UVC light
(shortest). Most UVC light does not reach the surface of earth. Why? Note, throw out possible
ideas that could create this. Brainstorm ideas and submit them. You won’t be penalized for being
wrong.
Problem 4-Freqency to wavelength and wavelength to frequency
I’ll do this one: The wavelength of radiation when you get an xray is 10.0nm. Find the frequency of the xrays.
• B) You try this one: The frequency of red light from a traffic signal is centered at 4.110x1014Hz. What is the
Problem 5- Frequency/Wavelength to energy
A) I’ll do this one: The frequency of radiation when you get an xray is 3.0x1016 Hz. Find the energy of
the xrays .
B) You do this one: The wavelength of red light from a traffic signal is centered at 729 nm. What is the
Hint: E =
ℎ
l
PLANCK’S QUANTUM THEORY
• When solids are heated they emit radiation.
• Planck discovered molecules can only emit light at specialized
energies or “quanta”
• A “quantum” is the smallest quantity of energy and is equal to:
h=6.626x10-34 J*s
Introduction to Blackbody
A) As the voltage is increased, what happens
to the light bulb ?
B) How does Wein’s Law relate to
incandescent lightbulbs of different brands ?
Challenge Problem
• A) ***A lamp rated at 40 W (1W= 1J/s) emits violet light of wavelength 470 nm. How many photons of blue light
can the lamp generate in 2.0s ? (Note on difficulty: I know that 3 stars is much lower than a typical challenge
problem, that’s because this is really only a challenge problem given that we haven’t really discussed these sorts of
problems yet, you will definitely want to be able to do this sort of problem before the exam).
Challenge Problem
• A) Synthesis****(same reasoning on difficulty as all synthesis questions): Black lights emit long wave UVA rays along
with a very small amount of visible light (seen as purple to our eyes). Does this mean we can develop skin and eye
cancer from black lights ? Why ?