Question

Light with a wavelength of 400 nm strikes the surface of cesium in a photocell, and the maximum kinetic energy of the electrons ejected is 1.54 x 10‐19J. Calculate the longest wavelength of light that is capable of ejecting electrons from that metal. (1 nm = 10‐9 m)

Answer 1

The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.

Step-by-step explanation:

Given that,

Wavelength = 400 nm

Energy
`E=1.54*10^(-19)\ J`

We need to calculate the longest wavelength of light that is capable of ejecting electrons from that metal

Using formula of energy

`E = (hc)/(\lambda)`

`\lambda=(hc)/(E)`

Put the value into the formula

`\lambda=(6.63*10^(-34)*3*10^(8))/(1.54*10^(-19))`

`\lambda=1292*10^(-9)\ m`

`\lambda=1292\ nm`

Hence, The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.