The surface of a metal, which has a threshold frequency of 6.93 x 10^14 s -1 , i

Question

The surface of a metal, which has a threshold frequency of 6.93 x 10^14 s -1 , is bombarded with a light with a wavelength of 353 nm. What is the kinetic energy of an electron is ejected from the surface of this metal?

A. 4.59 × 10–19 J

B. 5.63 × 10–19 J

C. 1.04 × 10–19 J

D. 7.26 × 10–19 J

E. 1.02 × 10–18 J

Can someone help me with this? I know the answer is supposed to be C but when I do the work I end up with strange answers.

[(6.626x10^-34)(3x10^8)]/(353x10^-9)=5.63x10^-19

After that I thought I had to do 5.63x10^-9/[(6.626x10^-34)(6.93x10^14) but I ended up with none of the choices. Please tell me where I went wrong.

Explanation / Answer

KE = energy bombarded - thershold energy
= h*c/ - h*f
= (6.626*10^-34 * 3*10^8)/(353*10^-9) - (6.626*10^-34 * 6.93*10^14)
= 5.631*10^-19 J - 4.592*10^-19 J
= 1.039*10^-19 J
which is approximately 1.04*10^-19 J

Answer: C

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