Class 12 Physics| Photoelectric Effect | #15 Frequency Change & Stopping Potential | For JEE & NEET

[@jyotirai9931]

Ashish sir is the best

[@akaashadhikari7662]

i think at zero stopping potential the photoelectric current is maximum...so the graph must not increase in the positive V axis(photoelectric current must be constant)

[@MohakudJi]

Hi are you doing right

[@gauravyadav6035]

No bro ,those electrons which come out from metal with zero energy can't reach to anode without potential difference.

[@santagaming09]

Bro potential to chaahiye wrna electrons emite nai hoenge

[@shaileshthombre2146]

Sir you are the real hero of india

[@AKASH-ls3zq]

Sir intensity depend both on frequency (neu) and number of photons per second (n). When colour of light(neu) constant then intensity high means number of photons(n) high....it is okay. But if colour of light (neu) different then in same intensity (I) how number of photons ( n) can be same????. NCERT says that even in different colours of light , intensity same means number of photons same. I can't understand; plz explain me sir😥😭

[@prashantchandravanshi3002]

Sir , for 2nd saturation , freq. is more i.e. electrons have more KE , so less amount of voltage should be required to pull up the e- cloud then why pinch off potential is same in both cases. why not less for 2nd one.

[@physicsgalaxyworld]

Pulling whole electron cloud means to pull the slowest or zero speed electron which is same in both cases...

[@prashantchandravanshi3002]

+Physics Galaxy Thank you sir...

[@prasantkpatel]

then pinchoff voltage should also be same for two lights with different intensities......because in that case also slowest electron will be zero speed electron only......then why it was different as per ur previous video

[@physicsgalaxyworld]

It is because before pulling the slowest electron first space charge needs to be pulled completely and at different light intensities space charge is different... but yes difference will be very small but not at same pinch off voltages....

[@prasantkpatel]

+Physics Galaxy ....thnks sir....u r just great....the only teacher in entire you tube who cleared each and every doubts i asked till now nd that too to the earliest!!

[@nev861]

Sir, at 2:13, why will the current be more at zero potential? Frequency does not the affect the magnitude of current right?

[@physicsgalaxyworld]

No... at higher frequency the initial kinetic energy of ejected electrons will be more so more electrons will penetrate the space charge... frequency does not affect the magnitude of saturation current after pinch off voltage...

[@nev861]

Thanks for clarifying sir.

[@BK-Aditya111]

Why does pinch off voltage remain same on increasing frequency

[@asutoshpal6497]

Sir ,I have a doubt.if V=0,no battery is connected to the metal plates ,does increase in frequency increase the photocurrent initially

[@aradhnakumari657]

Sir one question arises in my mind... Frequency must have an effect on photocurrent. A/c to the formula I = n h v where n is no of photons crossing unit area in unit time and v is frequency. 1. Now my question is if we increase frequency then intensity also increases which must increase the photocurrent??? 2.If we increase frequency by keeping intensity constant the in formula n decreases.So no of photons decreas then photocurrent must decrease?? But it is said that frequency has no effect on photocurrent.It only increases the ke of emitted electrons. Why?? Please reply and ckear my confusion..

[@vatsalgoyal4711]

1.on increasing frequency u have assumed constant photon flux(n) so still there are same no of phtons per unit time per unit area hence current is same as one photon ejects only one electron

[@vatsalgoyal4711]

Photo current actually depends on photon flux.. not on intensity

[@vatsalgoyal4711]

2. Yes what u wrote is correct(2nd point)

[@swarnendu4137]

@@vatsalgoyal4711 It is said that if we increase the voltage after pinchoff voltage then only speed of photoelectrons will increase not the number of photoelectrons...so current will not increase and that current is called saturation current. But charge per unit time is current. So if the speed of charge is increased then number of photoelectrons reaching to collecter should also be inscrease . So current should inscrease ? Anyone please

[@whosup3802]

Thank you sir:))

[@yashagarwal9080]

sir ,why the current at zero potential is more in freq v2 then in v1 ,as in both the frequencies no of ejected photoelectron are same. please explain I am getting confused in this concept

[@physicsgalaxyworld]

+Yash Agarwal no of ejected photo electrons are same but a a given voltage the no of photoelectrons ejected by higher frequency having higher energy are more as low energy electrons are stopped by the space charge near cathode... so at a given voltage at higher frequency current is more as more electrons are approaching the anode but at pinch off voltage all ejected electrons start reaching the anode so saturation current becomes same...

[@abhishekkumar-cl1jo]

but sir here the voltage is zero hence the ejected electrons will experience no opposition in their path(by battery) . also the no. of ejected electrons are same only they differ in KE therefore the current should have been same. I agree with you on the above statement but that is a general case . here it is a particular case of V=0

[@abhishekkumar-cl1jo]

I mean to say that at V=0 there is no space charge which will oppose the electrons. so current in both situations should be same. pls clear my confusion

[@physicsgalaxyworld]

It is not so... as at V=0, no attraction by the other electrode so those electron which will be ejected by almost zero KE will get collected outside the cathode and accumulate as space charge whereas higher KE electrons will penetrate the space charge and constitute the current... and further when more electrons will be ejected all slow electrons due to repulsion by space charge will contribute in increasing the space charge...

[@abhishekkumar-cl1jo]

then why not the same thing happen there ,where we say that the current will be same bcz only the KE of ejected electrons inc. and the no. of ejected electrons reaching the other terminal per unit time is same only diff is that they rach a bit faster.there also they should have got collected and inc. the space charge and make it difficult for the electron of less KE to penetrate the space charge and the current should have been different for different frequencies

[@yashagarwal9080]

thanks a lot sir 😊☺

[@alphaiitd1]

Thqnks sir

[@sarikaawasthy1456]

Sir,what does the Y intercept of this graph represent? Can we use it to compare work function for same stopping potential (Same x intercept)?

[@akashpaila6094]

Sir I think it will be y = mx-c but you wrote mx+c is incorrect I think because in the 2 ND graph what you had drawn represents it actually y = m x -- c But sir if in case what you wrote is correct then please explain me that thing ......... 🙏🙏🙏🙏🙏🙏🙏🙏🙏🏼🙏

[@vm7240]

Sir, i have watched the 9th video and i know that for higher freq. KE of EJECTED electrons will be more. hence, current will be same because KE (and so velocity) of e- is same as before in the wire (in circuit). But sir, here if KE of ejected e- s will increase, they will flow faster in the wire. so charge per unit time (current) should increase. Where am i wrong, sir? pl help...

[@mamataroutray1422]

KE is independent of intensity and photoelectric current...if KE will increase then the velocity of photoelectrons will increase....that"s why photo e-s move faster in the wire but the no. of e-s will constant...so current will constant

[@simranmalhotra3865]

Best explanation.. Thanks a lot Sir !!

[@ritapattnaik4359]

sir how can we quantitatively determine pinchoff voltage and on what factors pinchoff voltage depends

[@physicsgalaxyworld]

it is obtained experimentally only...

[@kunwarnayak3195]

Sir do something with your audio

[@raniyamuthu]

sir could u pls add a link of what u are writing

[@poonamsadwal2898]

i just can't understand you ....

[@physicsgalaxyworld]

+Garima Sadwal Can you pl explain what prob you are facing...

[@udaydeopa6054]

@Milan D Vijay hahhahaa

[@aatifboy8119]

Chal ba pta n kya bhok rha h😡😡😡🤬🤬

[@RahulPandey-rc9in]

Bad explanation.. totally messed up.. feels like u r just reading speech..no connect whatsoever with what you are trying to explain

[@AstroGuruRatnaVerma]

Rahul Pandey Please watch previous videos too

[@anmolempire1197]

Hey don't suddenly Jump on random lecture...Watch sequence wise carefully.. If you have good barin than knowledge and Explanation will penetrate into your mind..And you will appreciate sir lecture

[@badhil4468]

@@anmolempire1197 which year aspirant are you?

[@ayush1643]

try to study basic first

[@ayush1643]

@@prezputin2233 😂😂

[@narcos4739]

uncleji dhire bolo ...

[@ayush1643]

Beta ji kan me kapde dal lo Faltu ke excuse mat do

[@udaydeopa6054]

Pata bhi hain kya aur kis se bol rha hain

[@aspiringscientist1616]

@@prezputin2233 Putin op

[@shivansh709]

@@prezputin2233 😂

[@kritharthbaishnab]

helmet pahankar class mat liya karo