# Calculate the threshold wavelength of the metal.

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#### Chikis

• Jr. Member
• 35
##### Calculate the threshold wavelength of the metal.
« on: 21/07/2014 01:46:13 »
Caesium metal of work function $$2.0 eV$$ is illuminated with radiations of wavelength $$5.0\times10^{-7}m$$. Calculate the:
(i)threshold wavelength of the metal;
(ii)maxium energy of liberated elecrons.
$$[h=6.6\times10^{-34} Js; IeV=1.6\times10^{-19} J; c=3.0\times10^8 ms^{-1}]$$

Since threshold frequency and threshold wavelenght are not the same, am confused of the formula to use.
What is the best formula to use? Should I use $$\omega=hfo$$ or should use
$$E=\frac{hc}{\lambda}$$

#### evan_au

• Neilep Level Member
• 4257
##### Re: Calculate the threshold wavelength of the metal.
« Reply #1 on: 21/07/2014 10:20:49 »
Would it make more sense if you used the definition that Frequency f = c/λ = (Speed of light)/wavelength.

Perhaps those equations are equivalent?