Quantum physics and wave lengths

[poohead]

Homework Statement

What is the de Broglie wavelength of an electron that has been accelerated through a potential difference of 1 MV ( you must use the relativistic mass and energy expressions at this high energy.)

ans. 8.7 x 10^-13

Homework Equations

M= Mo/ square root (1 - v^2/c^2)

The Attempt at a Solution

I have no idea where to go with this question i am completely stumped, can someone please steer me in some direction to understanding such and getting the right answer, thank you and i really appreciate it.

 

[buffordboy23]

The question offers plenty of clues of where to start.

The desired answer is the de Broglie wavelength. Therefore, you could start at the end and work backwards. Do you know any equations for the de Broglie wavelength that might help you solve the problem? I know one that sticks out immediately; this equation relates the wavelength to only one other variable. Once you determine what this variable is, can you link it to the given data of the problem? If so, then problem solved.

 

[poohead]

well i assume now you use wavelength= h/mv and to find v i'd use Ee=Ek, just i need to find relativistic mass and energy first for the speed ill get is faster then that of light

 

[buffordboy23]

Here is an important difference for the momentum: p = mv (non-relativistic), p = $$\gamma$$mv (relativistic).

De Broglie's original formula is

$$\lambda = \frac{h}{p}$$