Problem #94 The Mysteries and Wonders of Light

Wave - Particle Duality

[Abhaykasturi]

The energy of light (photons or waves) remains constant. As the velocity change s, the wavelength changes.
E=hv where v is the frequency
v=the ratio of the velocity of in the medium to the wavelength of light in that particular medium.
Sir,
Please make a video for the answer and
always try to puzzle us with your questions.
Thank you

[jeevankunde]

just now my online tutor told about prof lewin"s video where he hold a bob near his chin and then realesed it we requested him to do so bt he said " i love myself more than pysics" then i realised how great are you hats off to to lots of love from maharashtra ( INDIA)

[khunjjs]

sir how are you these days? How is your health?

[HamidShafaee]

When the Light wave incidents a new lossless medium, then, there would be 3 kinds of distinguish waves: 1- Incident. 2- Reflected. 3- Transmission. By Fresnel's laws can prove: [Incident Power = Reflected Power + Transmission Power]. Of course this is wave perspective of light!. The amplitude of transmitted wave is lower than the incident wave. Et < Ei and Er <Ei.

[huashunkong]

wave-particle duality indeed amazed me!

[shubhamraj]

Hello sir...hope you will be fine at home...
Sir energy will change or energy will be less when going from rarer to denser medium because as we define refractive index the complex part of it represnets the "absorbed light" or "absorbed index" and these absorbed energy oscillate the electrons that also produces a em wave and the net effect is a phase shifted wave that we see...but normally in most of the transparent substances like glass
[in the equation of refractive index, that im not able to type it here, sorry for that] the imaginary part of the denominator, i(gamma)(omega) is smaller than [(omega)0^2 - (omega)^2]
[ where (gamma) is damping coefficient of oscillating electrons due to source light, (omega)0 is resonant frequency of electrons and (omega) is angular frequency of radiation] we dont observe this phenomenon to large extent.
Also in refraction some pf the light gets reflected also (partial reflection) so some energy goes there causeing loss of energy...

So its my explanation correct me if im wrong...
Thankyou sir...

[sahilbait]

Blessed to have a teacher like you, from INDIA ❤️

[johnwheeler]

I have severe anxiety problems and panic attacks, which have caused me to have to quit college more than once. Thanks to you, I am able to study physics as I have always wanted to do. You are a wonderful person and educator, thank you for posting your videos.

[andreathecat]

I am so amazed that "natural facts" like refraction that I assumed to be well-know to me, still contain question that leaves me stuck and puzzled and that I never thought about before. THANKS professor Lewin for bringing such interesting questions to our attention! Thanks for being a never-ending source of delicious enigmas that wake up our minds and lead to a so deeper understanding of the magic of Physics! THANKS!

[tanmay_academy]

Sir I am 13 years old .I purchased your book and I read it, you made me love physics . Respect from India 🙏🙏🙏

[rijulbarot]

The energy remains the same. From v=Freq*lambda, we can say that when the speed increases or decreases, it is due to increase or decrease in wavelength only as frequency remains constant and depends on source. So if v increases by a factor of k, the wavelength increases by a factor of k.
Energy is given by hv/lambda or hf and since frequency is constant, energy is constant.
If this is right pls reply prof Lewin as this would honestly make my day.
Stay safe professor <3

[aasemagina]

You have a great way to explain... Love you professor from Egypt.. ❤❤

[vishnumuralidhar]

♥ for W.L ♥ for Physics ♥ from 🇮🇳 . You are making us loved for physics everytime I see u. So much respect for you sir. Hope you are doing good with your health.

[hussainshaik]

no words to say about how much love u have towards children

[sanskarlife]

Sir I am in 12th standard in Orissa from a middle class family. I purchase ur book by selling my mobile phone and it really make me to know the beauty of physics

[kenlogsdon]

Prof. Lewin, here is what I believe about light, and what I have never seen explained: There is only ever a full spin boson exchanged between two half spin fermions. That is the "particle" part of the interaction.

The path over which that exchange takes place is determined by the path wavefunction, which is the sum of all possible paths between emitter and absorber for a boson of a particular energy. (Which is indeed very hard to calculate since one must take into consideration all the possible ways the paths add up and cancel out, leaving only the actual paths with varying probabilities.) That is the "wave" part of the interaction. The path wavefunction always exists between any pair of fermions; there is no "collapsing" of the path wavefunction when the boson is exchanged (let alone "observed"), that is a complete misconception.

The interaction itself is transtemporal; there is no distance and no elapsed time between emission and absorption in the boson frame. The ridiculous and all too common picture of a "photon" being a "little packet of waves" flung randomly across space at the speed of light is clearly incorrect. A "photon" is more like a transfer of energy directly between a specific emitter and a specific absorber that takes place with no medium of propagation. The question is, how does that actually work (and for that matter, why is the probability of the interaction ~1/137 in the case of the photon)? After all, the relativistic spacetime interval still applies, and constrains the speed of the interaction.

That, to me, is the fundamental question that needs to be addressed when talking about the unification of QM/matter and GR/spacetime, IMHO.

[sainikmukherjee]

I dont know if U reading this comment, I am a researcher and the basics of mechanics & electronagnetism I have learnt deeply 😍from U.I am student of urs by heart.Love from India.U are an inspiration as I too am an educator of physics here...

[parthibsaha]

I don't know much about this thing.But may be if light is a wave then when it passes through water it has to overcome more barriers due to water being optically denser than air so its speed is low. It's almost like a car running on a smooth road and suddenly entering a muddy area where it has to overcome more friction and so energy gets dissipated but as the power is same when it will get out of that mud the speed will increase.I don't know if my explanation is right.May be it's funny😅

[RetainTheDark]

Since the light going from air to water will be of the same color, i.e. if white light goes from air to water, it still remains white and therefore its wavelength (lambda) does not change. If the wavelength does not change, it implies that its frequency also doesn't change. Energy = h*(v) where v is the frequency, and since lambda remains the same and thus frequency remains the same and h is already a constant, therefore according to the equation the energy of light also does not change.

Regards

[serene]

Hello Sir! My physics teacher insisted that I saw your videos and I don't regret it! 😊