Question

Platinum, which is widely used as a catalyst, has a work function  (the minimum energy needed to eject an electron from the metal surface) of 9.05 × 10–19 J. What is the longest wavelength of light which will cause electrons to be emitted?

Answer 1

Answer:2.21 x 10^-7 m

Explanation:

From the question we know that,

Phi = 9.05 x 10^-19 J

Now with Vo being the threshold frequency and h being Plancks constant, then the threshold (i.e. MINIMUM) frequency required to ionize the metal is:

Vo = 9.05 x 10^-19 / 6.626 x 10^34 J.s

= 1.36 x 10^15 s^1

The MAXIMUM wavelength this corresponds to is

Landa = C / Vo = 3 x 10^8 / 1.36 x 10^15

Wavelength = 2.21 x 10^-7m

= 2.21 x 10^-7 nm