how does the max wavelength that light can eject electrons from a meterial help me find the speed of electrons ejected when a ray with smaller wavelenght is incident?
2007-07-20 01:25:14 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Try:
E = hv
This can be used with the known max wavelength to see the energy of light needed to eject the e-. Then use this value of energy and the wavelength of the incident wave to calculate the speed of the e-.
2007-07-20 01:41:31 · answer #1 · answered by physandchemteach 7 · 0⤊ 0⤋
The max wavelength that light can eject electrons can be used to calculate the minimum energy (Em) required to eject electron. Now when a ray with a smaller wavelength is incident part of that ray's energy (Em) is used to eject the electron, and the remaining energy will be the Kinectic energy of the ejected electron (1/2mv^2) and so you can find the speed of the electron.
If the energy of the incident ray with the smaller wavelength is E, then mathematically:
E - Em = 1/2 mv^2
2007-07-20 08:59:26 · answer #2 · answered by Southpaw 5 · 0⤊ 0⤋
The maximun wavelength corresponds to the smallest frequency. The energy of this photon is the amount of energy the electron needs to get out of the metal. Now, if you have another wavelength, find the energy of this new photon and subtract off the enrgy for the electron to get out of the metal. This leaves the end kinetic energy of the electron, and hence the velocity.
2007-07-20 09:00:32 · answer #3 · answered by mathematician 7 · 0⤊ 0⤋
The maximum wavelength ‘ λo’ corresponds to the minimum frequency.
Hence the minimum energy required to eject one electron is hÏ
o = h c / λo
Ï
o is the minimum frequency.
If smaller wavelength λ is now incident on the metal, then its frequency is c/ λ and its energy is h c/ λ
[h c/ λ] – [h c / λo] = ½ m v^2 the kinetic energy of the electron emitted.
2007-07-20 09:38:44 · answer #4 · answered by Pearlsawme 7 · 0⤊ 0⤋