The Electronvolt – A Level Physics

Published on February 23, 2015 by

In everyday life we use the joule to measure energy. When we consider the energy of individual particles or photon it is often more convenient to use a smaller unit, the electronvolt, eV.


What exactly is a photon? this video shows how we can use the particle model, with individual corpuscles of energy, to explain certain properties of EM radiation.

If you want to find out more about the photon then I can highly recommend you listen to this radio show:

Thanks for watching,



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  • AlchemistOfNirnroot 7 years ago

    Have you done/ or know of videos which help with converting from kg —> neVc^2 and vice versa? Where n can be M, G or T.

    • Physics Online 7 years ago

      +AlchemistOfNirnroot I don’t have any videos on that yet I’m afraid.

    • AlchemistOfNirnroot 7 years ago

      @A Level Physics Online Do you know what it’s called or how I should research it? It’s one of the more annoying questions in A level Physics for me. 

    • Physics Online 7 years ago

      +AlchemistOfNirnroot I guess if E=mc^2 then you can rearrange this to make ‘m’ the subject. m = E/c^2. If you have the energy in eV then first convert this to joules, divide by the speed of light squared and that should be the mass in kg.

    • AlchemistOfNirnroot 7 years ago

      @A Level Physics Online Thanks. Do you do A2 topics? e.g Circular motion, capacitance, faraday-lenz law etc. 

    • Physics Online 7 years ago

      I have just finished a video on Faraday’s and Lenz’s Law this minute! Spooky. I have these A2 videos on my other channel: 

  • madscientistbro 7 years ago

    It would have been better if you had included all the units in the intermediary step starting at 1:40.

  • MisterBinx 7 years ago

    I trust a guy with an accent teaching physics.

  • Samie Mohammed 6 years ago

    this is kinda a random question but do you have a video on how to reduce uncertainty in any experiment. I have a feeling for the new specification they are going to put heavy emphasis on uncertainty in section c

    • A Level Physics Online - Year 13 6 years ago

      +Samie Mohammed Not one of this specifically I’m afraid.

  • Muhammad Ali Musani 6 years ago

    When can you use KE=eV and when can you use KE=1/2mv^2?

    • usef bmf 6 years ago

      Muhammad Ali Musani so ev=0.5*mv^2 isn’t it

    • Muhammad Ali Musani 6 years ago

      Hey Usef, sorry, I did this a little while back.
      KE=eV when finding the KE of an electron between 2 charged metal plates: this tells you how much work the pd is doing on the electron. So yes you could say, at the end, eV=0.5mv^2.
      Meaning, a higher P.d would give a larger final velocity.

    • usef bmf 6 years ago


  • Aryan Jain 6 years ago

    Since electron is gaining kinetic energy of 1eV won’t it be losing equivalent amount of potential energy since Potential energy change would be equal to -1.6*10^-19 J so mechanical energy remains conserved

  • usman aslam 6 years ago

    SLOW DOWN!!!!!!

    • Adxm27 5 years ago

      usman aslam or just replay…

  • Lamya Sms 5 years ago

    thanks i was lost in this one

  • Abhishek Bhattacharjee 5 years ago

    this helped me solve a lot of confusion, thanks fr the vid.

  • Entertainment Overloaded 5 years ago


  • Aditya Misra 4 years ago

    The teaching part went a bit too fast I kept on pausing. But I still understood some parts.

  • ARNAV SINGH 4 years ago

    isnt that a LEGO block?

  • Jose 4 years ago


    • oldcowbb 2 years ago

      Excellent work today Jose. Keep it up.

  • Howchen 4 years ago

    Very clearly explained

  • Mairaj Khalid 4 years ago

    Your English is too fast I don’t understand your topic

    • Perspective Matters 4 years ago

      I think his main audience are native English speakers. If he spoke more slowly, he would loose some of that and gain a little bit of international community. This doesn’t help many internationals as A-level Physics isn’t that relevent and the sum target audience would be reduced.
      Hence I don’t think this will change.
      However YouTube allows slower playback.

    • MonkaS 4 years ago

      Mairaj where u frm ?

    • Mairaj Khalid 4 years ago

      @MonkaS turkey

  • SpiritualFoxPlays - Try hard Player 4 years ago

    Hey man, after watching a few of your videos including young’s double slit, I must say you really made me understand physics better as you sound confident in your answers as well. So I just want to say thank you and have a great day, sir!

  • Rose 4 years ago

    thank u that was helpful

  • Tate Apcher 3 years ago

    Who’s bingeing these videos right before their exams

  • david gorelle 3 years ago

    Alright cool, good to know. But what does Pd stand for?

    • Physics Online 3 years ago

      Potential difference (voltage)

  • Subaharan Muruganathan 1l 3 years ago

    You have just earned a sub my friend

Comments are closed.