Class 12 Physics | Photoelectric Effect | #9 Effect of Variation in Frequency | For JEE & NEET

[@anmolempire1197]

On increasing frequency not absolutely not impilies current increase...As one photon (hu>∅) can only & only ejected single electron..As increasing frequency means more stronger wavelength will incident on metal surface and hence it will eject the electron with more KE and not more than one electron i.e.2e..As one can uniquely eject one electron only provide (hv>∅)...

[@iuoyo4707]

If u have doubt that why current doesn't depend upon frequency even if it increases velocity of electrons , Refere here : I = Q/T Q = e × no. of electrons per unit area × area on which they are incident So Q= no. Of electron per unit area×k Where k is constant, I = no. of electrons per unit area ×k/T And no. of electrons per unit area /T is photon flux which is constant So current= k' , which means it is constant. So mathematically this was explaination.

[@shr1126]

After a lot of research I made my mind to understand! Here's what in my mind Think red light (donno wavelength nd frequency, think one number 😅 950 and 620 think) If red light ejects an electron, Arre vo work function ke equal energy deta hai raklo! Then one wave aake ek electron ko marke uda diya ek sec me If voilet light radiates to same surface usko jyada energy hai red ke bhi jyada think 850 frequncy, vo red ke jaise hi hit karta hai in same time per that area where it is hitting! But after hitting aur 330 frequency ka energy bacha hai na usse vo fast chal tha h , yaha photo current, electron vo surface se bahar aana, dono me same time pe same hi baahar aata hai, aane ke baad violet ka fast chalta hai We all think after increasing frequency vo bahar jaldi se aata hai na, vahi distance ko tej se cover kar rhe na, usko photo current bolenge, but it's wrong usko nhi Surface se electron bahar (I told just surface se) vahi time hai jo red aur violet nikaltha hai ise photo current same kahenge , but after ejection violet ka tej bagtha hai but use ham nhi kahenge current! 😅 Ye tha mera view Sahi hai to like nhi reply karo! 😅 Nhi samaj aaya tho, doubt poochlo! 😅😅

[@pavanbhat3861]

It's right. One photon can uniquely eject one electron corresponding to it's work function and the remaining energy is used to increase the kinetic energy of the electron. The reason photocurrent changes on increasing intensity is because you are providing more photons itself in the first place. So the rate of ejection will also increase thereby increasing photocurrent. It's not the same case on increasing frequency because the RATE of ejection doesn't change.

[@arandombeing7262]

Your comment is correct. I also thought exactly this only. But i got confused when in the animation, the electrons in the wire is moving fast. The animation over here is wrong. The electrons in wire WON'T move faster when frequency is increased.

[@alphaiitd1]

Thanks sir

[@yashagarwal9080]

let suppose 1e is passing through ammeter in 1sec before increasing frequency of light ,as after inc frequency k.e. of electrons is increased so 2 electron (say) are passing in 1 sec ,therefore current must be changed ..please correct me sir.

[@physicsgalaxyworld]

+Yash Agarwal if in one second total 10 e are ejected from the cathode then maximum 10 e can reach the anode so current is 10e no matter at what speed they are moving... if ejection rate is fixed, current cannot increase... think again carefully... its just they are reaching early but fix nos in one second....

[@theexperiment9105]

How the photo flux can be constant on varying frequency

[@iamcomputernerd1239]

@@physicsgalaxyworld But persecond there will be higher no. of en hence current

[@anmolempire1197]

@@iamcomputernerd1239 absolutely not...As one photon (hu>∅) can only & only ejected single electron..As increasing frequency means more stronger wavelength will incident on metal surface and hence it will eject the electron with more KE and not more than one electron i.e.2e..As one can uniquely eject one electron only provide (hv>∅)...

[@shr1126]

@@anmolempire1197 thanks brother 🎀💓💓💓🎀

[@kumarsambhav6844]

Sir just curious to know, How much time does it take to make one animation ?

[@physicsgalaxyworld]

3 hrs to 30hrs...

[@zyro9922]

Thank you ∞ sir.

[@arunteltia7888]

Really omg!!!!!!!!!! Thank u sir i love you sir u are the best

[@CristianoRONALDO-nw8hr]

@@physicsgalaxyworld you are great sir.

[@sejalsangole2527]

@@physicsgalaxyworld Reallyy!!..Thanks a lot sir!!!!!

[@gigachadkartik]

Sir if photons are ejected very fast then due to earthing electron from earth will come very fast to neutralize the metal and as current is defined as time rate of flow of charge then it must also increase isn't it?

[@physicsgalaxyworld]

Current is limited by the photon flux of radiation beam... as no of photons per unit time incident are constant so current will also remain constant...

[@cricobug9778]

@@physicsgalaxyworld could not understand sir,but time rate of flow is decreased current should increase

[@parallax75]

@@cricobug9778 same doubt 3 years later

[@fatimaseliya8801]

@@parallax75 one photon can remove one electron so number of photon incident on metal remains same so the number of electrons ejected also remains same. Even if the electron are moving fast as velocity increase but the metal surface is not ejecting electron. Bhai bhale hi car fast chal rahi hai par car ek particular time me ek point se nikal ne wali same number me hi hai

[@kumarutkarsh1248]

Sir why frequency does not affect number of electron emitting out I mean if we increase the frequency then electron in the metal sheet will have more KE and therefore those electron that were not able to emit out due to internal collision will now be left with some KE even after collision so number of electron emitting out must be increased

[@Future_iitian_]

Same doubt

[@warriorbjyt9535]

sir if photons are ejected fast we can say that their drift velocity is more so by I= neva current should be more pls explain

[@slightlybettertoday6204]

My doubt is... On increasing frequency shouldn't the quantum efficiency increse. I mean, previously there were electrons which let's say after n collision didn't have enough energy left to leave the metal surface... But now since it had more intial energy than before, it could be possible for that electron to leave the metal surface after the same n number of collision ...thereby increasing the quantum efficiency.

[@adilh3908]

sir plz upload dual nature of matter and radiation plz

[@aspiringscientist1616]

No

[@SUSHANTSINGH-bh4ef]

Sir this is sufficient for jee mains

[@rmishra1000]

More than sufficient

[@vinayvinnu9808]

@@rmishra1000 for neet???

[@ayush1643]

sufficient for advance also additional things that you need to do watch advance illustrations and do lots of practise

[@shivanshpandey7957]

😇😇😇😇😇

[@rmishra1000]

Sir, if photons of frequency v are falling on metal surface then n no. of electrons ejected per second,is all of them have same maximum kinetic energy if yes then(collision of different e is different and they loses different quantity of energy while collision time interval, so they also posses different Max. K. E.). If no then why?

[@zyro9922]

I think everybody watching got this doubt "Why doesn't photoelectric current increase with frequency of the incident wave?" physics.stackexchange.com/questions/222359/why-doesnt-photoelectric-current-increase-with-frequency-of-the-incident-wave This helped me.

[@physicsgalaxyworld]

current is rate of flow of charge (coul/sec) and by one incident photon one electron is emitted... if you increase frequency, it does not change the photon flux (no of incident photons per unit area per sec) thats why current is not affected by frequency variation....

[@zyro9922]

It was a very easy concept but still it took time to grasp it.

[@anitamalik1151]

Mst samjhaya iss link na

[@parallax75]

Ali hassan bro thankyou so much💯🔥

[@shr1126]

@@RaviRanjan-wx8vm bhai samaj aya kya?

[@soumitradas8463]

All those who are not able to understand why current didn't change. I think sir wants to mean that photon flux did not change hence rate of ejection of e- will remain same but i guess the speed at which electrons go away becomes faster. Again, u can understand like this," e- gets ejected just like the previous frequency and some natural extra force comes in and gives it a push for higher speed hence the process of ejection in the case of both frequencies can be considered similar and current remains constant in both cases. Sir pls correct me if i m wrong..

[@physicsgalaxyworld]

Upto some extent you are correct... as frequency increases it gives electron extra energy so ejected electron KE increases (but not due to any extra force) and as photon flux is constant no of electron per unit time remain constant so charge/s or current remain constant...

[@roneet9027]

thank you sir