Platinum, which is widely used as a catalyst, has a work function φ(the minimum energy needed to eject an electron from the metal surface) of 9.05 x 10-19 . what is the longest wavelength of light which will cause electrons to be emitted?
a. 2.196×10-7m
b. 4.553×10-6 m
c. 5.654 x 102 m
d. 1.370 x 1015 m
e. > 106 nm

A.

Explanation:

The work function of the Platinum =

For maximum wavelength, the light must have energy equal to the work function. So,

Where,  

h is Plank's constant having value

c is the speed of light having value

is the wavelength of the light being bombarded

Thus,

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.