Necessary to remove an electron from the surface.

[omni]

it known that photon of Electromagnetic radiation Cause to an electron emission from Metal surface.
the velocity of the electron is 3.6*10^3km/h

i Calculate the Wavelength of the electron with the formula $$\lambda$$=h/m*v

it is written that when the frequency radiation are low than 2.5*10^16Hz so there are no any electron emission from the Metal surface.
now i asked to find how much energy are necessary to remove an electron from the surface.
so i need to use the formula 1/2me*v^2=hv-$$\Phi$$ all i need is to find $$\Phi$$ ?

thanks.

 

[SammyS]

...
so i need to use the formula 1/2me*v^2=hv-$$\Phi$$ all i need is to find $$\Phi$$ ?

thanks.

Hello Omni.

You are using the variable "v" in two different ways. The v on the left hand side is the velocity of the ejected electron. The v on the right, likely should be the Greek letter ν (nu), which is the frequency of the photon. ( You might rather use f for frequency)

c = λ ν, where c is the speed of light.
.

 

[omni]

yes that is correct.

"c = λ ν, where c is the speed of light." how this can help me here?
in this formula v is also mean nu (frequency )
but i need to find how much energy are necessary to remove an electron from the surface.

thank you.

 

[SammyS]

You need the electron's Kinetic Energy to be greater than zero : KE > 0.

Use that with:

(1/2)m_ev_e² = hf - Φ.

Find the frequency, f, then find λ .

 

[omni]

thank you again.

so tell me if i correct:
1/2*(9.109*10^-31*(3.6*10^3)^2)=(6.626*10^-34*2.5*10^16)-$$\Phi$$


till here i correct?

thank you.

 

[SammyS]

thank you again.

so tell me if i correct:
1/2*(9.109*10^-31*(3.6*10^3)^2)=(6.626*10^-34*2.5*10^16)-$$\Phi$$


till here i correct?

thank you.

It looks good to me.

 

[omni]

hi.

ok so all i have to do now is to find $$\Phi$$ by doing hf-1/2me*V^2 and we know the value of each of this formulas as i showed before.

so i do like this: (6.626*10^-34*2.5*10^16)-(1/2*(9.109*10^-31*(3.6*10^3)^2))=$$\Phi$$

hope you can understand something in this mess

really thanks for your help.