For more information, please see full course syllabus of AP Physics 1 & 2

For more information, please see full course syllabus of AP Physics 1 & 2

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### Wave-Particle Duality

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

- Intro 0:00
- Question 1 0:15
- Question 2 0:34
- Question 3 0:53
- Question 4 1:54
- Question 5 2:16
- Question 6 2:27
- Question 7 2:42
- Question 8 2:59
- Question 9 3:45
- Question 10 4:13
- Question 11 4:33

### AP Physics 1 & 2 Exam Online Course

### Transcription: Wave-Particle Duality

*Hi everyone and welcome back to Educator.com.*0000

*In this mini-lesson, we are going to go through page 1 of the APlusPhysics worksheet on wave particle duality.*0002

*You can find the link to that worksheet down below the video.*0008

*Let us dive right in.*0012

*As you do this, you are probably going to need a copy of the electromagnetic spectrum near you in order to answer the questions.*0013

*Number 1 -- Compared to a photon of red light, a photon of blue light has a...?*0019

*Blue has a greater energy than red light. It has a higher frequency, therefore it has a higher amount of energy -- Number 1.*0024

*Number 2 -- Exposure to UV radiation can damage skin and exposure to visible light does not damage the skin.*0035

*State one possible reason for this difference.*0041

*UV radiation has more energy because it has a higher frequency.*0043

*Number 3 -- Louis de Broglie extended the idea of wave particle duality to all of nature with his matter wave equation, λ equals Planck's constant divided by mass times velocity, where λ is the particles wavelength, (m) is its mass, (v) is its velocity and (H) is Planck's constant.*0053

*Using this equation, calculate the de Broglie wavelength of a helium nucleus moving with a speed of 2 × 10 ^{6} m/s.*0069

*If λ equals h/mv, that is going to be...*0077

*...well Planck's constant is 6.63 × 10 ^{-34}/6.7 × 10^{-27} kg (mass) divided by 2 × 10^{6} m/s (velocity) is going to give us a wavelength of about 4.95 × 10^{-14} m.*0083

*That is a pretty, pretty, pretty, really, really, really small wavelength.*0108

*Number 4 -- The wavelength of this particle is of the same order of magnitude as which type of electromagnetic radiation?*0114

*To do that I need to go to the electromagnetic spectrum where I find that that is very close into the realm of gamma rays.*0120

*Number 5 -- A photon of light carries -- well it carries both energy and momentum -- correct answer there is Number 3, photons have energy and momentum, but no mass.*0136

*Number 6 -- Wave particle duality is most apparent in analyzing the motion of small, small particles -- baseball, space shuttle, galaxy -- all big, but an electron is small, so this is most apparent for the electron.*0147

*Number 7 -- A photon of which electromagnetic radiation has the most energy?*0162

*Well, it is going to be the one with the highest frequency.*0166

*UV, x-ray, infrared, or microwave -- I will use the electromagnetic spectrum diagram to see that that is going to be Number 2, x-ray.*0168

*Number 8 -- Light of wavelength 5 × 10 ^{-7} m consists of photons having what energy?*0179

*To do this, energy is going to be equal to HF or HC/λ using the wave equation where V = F(λ) and our velocity is C.*0185

*So that is going to be 6.63 × 10 ^{-34} × 3 × 10^{8} m/s (c, the speed of light in a vacuum)/5 × 10^{-7} m (wavelength)...*0198

*...which is going to give us an energy of right about 4 × 10 ^{-19} J -- Answer Number 3.*0211

*Number 9 -- Electrons oscillating with a frequency of 2 × 10 ^{10} Hz produce electromagnetic waves.*0225

*These waves would be classified as...?*0232

*Well, if they oscillate at that frequency, the waves created would have a frequency of 2 × 10 ^{10} Hz as well.*0234

*Using the electromagnetic spectrum, I can look and find out that those fall into the range of microwaves -- Answer Number 3.*0242

*Number 10 -- The energy of a photon is inversely proportional to its...?*0253

*Now remember energy is (HF) or HC/λ, so wavelength -- Yes, it is inversely proportional to wavelength, so the answer must be Number 1.*0258

*Last question -- A photon has a wavelength of 9 × 10 ^{-10} m.*0273

*Calculate the energy of this photon in joules.*0278

*Well, again, energy is HC/wavelength, which is going to be 6.63 × 10 ^{-34} (Planck's constant) × 3 × 10^{8} m/s (the speed of light in a vacuum)/9 × 10^{-10} m (wavelength).*0281

*I plug that into my calculator and I come up with something pretty close to 2.2 × 10 ^{-16} J.*0300

*That completes the first page of the worksheet on wave particle duality. If you struggled with this, it is probably time to go back and review that lesson in the main portion of our lecture series.*0311

*If it went great -- Excellent -- Time to move on.*0324

*Thanks so much for your time everyone and make it a great day.*0327

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