What will be the energy required to make 1 electron escape?

[Tanishq Nandan]

Homework Statement

Homework Equations

E=hc/lamda

The Attempt at a Solution

I can get the amount of energy incident on the surface (3%of Intensity×Area)
What will be the energy required to make 1 electron escape?
(4.5eV+hc/250nm )?
Then I divide total energy by energy to make 1 electron escape.
Unfortunately,the calc gives the answer to be 2×10^10
Which ain't in the options..
Help appreciated.

 

[phyzguy]

Two comments:

(1) Read the problem again. Only 4% of the energy is absorbed, and only 3% of that is energetic enough to eject an electron.

(2) Why use the 4.5eV at all? The problem tells you what percentage of the photons are energetic enough to eject an electron. How much energy do those photons have?

 

[Tanishq Nandan]

How much energy do those photons have?

10^-6 Joules per second

Why use the 4.5eV at all?

Ohhk..Then I just equate 3percent of this energy to x times hc /lamda?

 

[Tanishq Nandan]

No..i think I mixed up things..

 

[RedDelicious]

It will help if you first think about what is happening physically. You have a bunch of photons hitting the surface of the sample. In order to be free any electrons, the photon has to first be transmitted. If it is transmitted, it has to also have enough energy to free the electron. To solve this problem it is hopefully clear that we need to know how many photons make it through these two stages.

Try to answer these questions.

In one second, how much energy is transmitted to the sample?

Now much of this transmitted energy is actually able to free electrons?

 

[Tanishq Nandan]

Ooo..ok,i got it.
We don't need the Work function because the question already gave us that only 3% OF 4% of the incident energy is already capable of emitting electrons.
I just need to equate 0.12% of incident energy to the energy of the ejected electrons.
Answer's coming
Thanks,both of ya