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?

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

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

answer and explanation;