Homework Help: General Chemistry

Posted by Kat on Sunday, January 13, 2008 at 4:54am.

The photogenic work function of a metal is the minimum energy needed to eject an electron by irradiating the metal with light. For calcium, this work function equals 4.34 x 10^-19 J. What is the minimum frequency of light for the photoelectric effect in calcium?

I'm confused so if you could break it down how you got the solution I will greatly appreciate it. Thanks again.

General Chemistry - drwls, Sunday, January 13, 2008 at 7:17am
The correct word is photoelectric, not photogenic. You used the correct word later in the question. Photogenic means something else entirely.
To solve this problem, set the photon energy requirement equal to the work function, 4.34 x 10^-19 J.
Then set that equal to the photon energy given by the Plank equation
h*f = 4.34 x 10^-19 J
where h is Planck's constant,
h = 6.62*10^-34 J*second
f = 4.34 x 10^-19 J/6.62*10^-34 J*second
The answer will be in Hz (cycles per second)

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