Midterm 1 Review - PowerPoint Presentation

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Slide1

Midterm 1 ReviewSlide2

Waves:

Given that yellow light is about 600 nm and blue light is 500 nm,

W

hich has the higher frequency?

Higher energy?

Lower wavelength, so blue light

Lower wavelength, so blue lightSlide3

Black Body Radiation

Graphical Reasoning/Synthesis questions

Given the graphs: Which would you expect to look “whiter” to the human eye, a lightbulb operating at 3300K or 2700K? Why or why not?

Synthesis: Would a light bulb operating at 5000K (assume it were possible to engineer this) be an efficient light source? Why or why not?

Our sun’s

l

max

is approximately 500nm. This is squarely in the green region of the electromagnetic spectrum. So is the sun green? Why or why not?Slide4

Wave

interference

The picture below shows water interfering in a way similar to how light interfered in the double slit experiment.

Which letter(s) represents the area where the waves are interfering constructively?

Which letter(s) represents the area where waves are interfering deconstructive?

If instead of water, this was light, which letter(s) would give rise to a bright spot on the film? If instead of water, this was light, which letter(s) would give rise to a dim spot on the film?

X and Z

X and Z

Y

YSlide5

Photoelectric Effect

Which has a greater threshold frequency?

If a laser of sufficient energy to eject electrons from either metal is used. And a pulse with the same number of photons is shown on each metal, which metal will eject more electrons?

If a laser of sufficient energy to eject electrons from either metal is used. And a pulse with the same number of photons is shown on each metal, which metal will eject electrons at a faster velocity?

You are doing an experiment replicating the photoelectric effect on two different metals. One has a work function of 5.90x10

-19

J, and one has a work function of 3.00x10-19J.

So the one with the greater work function must have the greater threshold frequency

Number of electrons=number of photons so they’ll both have the same number ejected.

Higher energy input= higher kinetic energy=higher velocity

 Slide6

Heisenberg

Uncertainty Principle

True or False: The Heisenberg Uncertainty principle does not allow you to know both momentum and position at the same time?

True or False: The Heisenberg Uncertainty principle is due to error in our measurements?

True or False: The Heisenberg Uncertainty principle is only true for matter?

True: this is the definition of the uncertainty principle.

False: it is an innate property of the universe.

False: it is true of light as well. Slide7
Slide8

DeBroglie Wavelength

Which has a longer wavelength, a proton or an electron? (don’t do calculations)

Can this equation be used to find the wavelength of light? How do you know? Which equations should you use?

Why don’t we see the wavelength of large objects?

A proton has more mass so it has a smaller wavelength

No, light doesn’t have mass, we use E=

hc

/

l

or

n

=c/

l

for light

The wavelength is too small in relation to the object.