Question

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

Answer 1

A.
`\lambda_0=2.196* 10^(-7)\ m`

Step-by-step explanation:

The work function of the Platinum =
`9.05* 10^(-19)\ J`

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

`\psi _0=\frac {h* c}{\lambda_0}`

Where,

h is Plank's constant having value
`6.626* 10^(-34)\ Js`

c is the speed of light having value
`3* 10^8\ m/s`

`\lambda_0` is the wavelength of the light being bombarded

`\psi _0=Work\ function`

Thus,

`9.05* 10^(-19)=\frac {6.626* 10^(-34)* 3* 10^8}{\lambda_0}`

`(9.05)/(10^(19))=(19.878)/(10^(26)\lambda_0)`

`9.05* \:10^(26)\lambda_0=1.9878* 10^(20)`

`\lambda_0=2.196* 10^(-7)\ m`