Wavelenght of the incident light

  • #1
wyclefchick
9
0

Homework Statement


An incident light shines on a mercury metal plate with a work function of -4.5 eV. The stopping voltage is observed to be -1.65 volts. What is the wavelenght of the incident light?


Homework Equations


wavelength=hc/E-0(it's a Greek sign n i don't have it in my computer)


The Attempt at a Solution


(4.14 X 10^-15 eVs) (3 X 10^8 m/s) / 1.65 + 4.5 = 1.242 X 10^-6 / 6.15

1.242(10^2)/6.15 = 20.1954

but the right answer is 201.7561 nm


so can anyone please tell me what did I do wrong?
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,223
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[tex]\frac{hc}{\lambda}=\phi +eV_s[/tex]

Did you use the correct value for h in eV?
 
  • #3
wyclefchick
9
0
i used h=4.14 X 10^ -15 am i supposed to use the other one? h=6.626 X 10^-34 ?
 
  • #4
rock.freak667
Homework Helper
6,223
31
How'd you go from 1.242 X 10^-6 / 6.15 to 1.242(10^2)/6.15 = 20.1954?

Because if you work out 1.242 X 10^-6 / 6.15 you'd get your answer.
 
  • #5
wyclefchick
9
0
I was following one of the examples that my teacher did in class.

well if i do 1.242 X 10^-6 / 6.15...it equals 2.01951 but the right answer is 201.7561 nm
 
  • #6
rock.freak667
Homework Helper
6,223
31
1.242 X 10^-6 / 6.15 =201nm
 

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