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**1. Homework Statement**

the maximum wavelegnth for which an electromagnetic wave can eject electrons from a platinum surface is 196 nm. when radiation with a wavelength 141 nm shines on the surface, what is the max speed of the ejected electrons?

**2. Homework Equations**

f=c/λ

E=hf

E=Φ+K

Φ=hf0

**3. The Attempt at a Solution**

λ=196nm

f=(3E8)/(196E-9)

f=1.5306E15

E=Φ+K

(6.63E-34)(f??)=(Φ??)+K

K=??

λ=141nm

f=(3E8)/(141E-9)

f=2.127E15

E=Φ+K

(6.63E-34)(f??)=(Φ??)+K

K=??

K1-K2=_______

K=1/2mv^2 to find v

but i dont know what numbers to plug in as f?? and Φ??

i tried putting in the f values i found using the given wavelengths but i kept getting K=0

please help

thank you for your time