Page 1 of 1

### When to use DeBroglie or Ek equation

Posted: Mon Apr 23, 2018 10:47 pm
Hello!

If the velocity is given in a problem, how do I know whether to use the DeBroglie equation(wavelength=h/p) or the Kinetic energy equation(Ek=1/2mv^2)?

### Re: When to use DeBroglie or Ek equation

Posted: Tue Apr 24, 2018 11:21 am
It all depends on what the question is asking. For example, if the question asks for the wavelength given mass and velocity, then you use the debroglie equation. if the question asks for KE or the maximum energy of electrons you use the Ek equation.

### Re: When to use DeBroglie or Ek equation

Posted: Tue Apr 24, 2018 2:07 pm
You use DeBrogile when given a mass value.

### Re: When to use DeBroglie or Ek equation

Posted: Wed Apr 25, 2018 8:25 pm
For example, light doesn't have any mass that is why we are unable to use DeBroglie's equation to find E.

### Re: When to use DeBroglie or Ek equation

Posted: Wed Apr 25, 2018 10:45 pm
On my notes, I have written that the DeBroglie equation does not apply to light since light doesn't contain mass.

### Re: When to use DeBroglie or Ek equation

Posted: Thu Apr 26, 2018 12:04 pm
In addition to what everyone said, think about the context of the problem. You typically use the kinetic energy equation for the photoelectric effect and a situation describing it whereas the DeBroglie equation relates a moving particle's wavelength to its momentum, mass*velocity.

### Re: When to use DeBroglie or Ek equation

Posted: Thu Apr 26, 2018 10:44 pm
If we have to use the DeBroglie is it certain that the mass will always be given for a problem?

### Re: When to use DeBroglie or Ek equation

Posted: Sun May 06, 2018 2:04 pm
Any moving mass will have a wavelike property with wavelength of λ, this equation is DeBroglie Equation which is λ=h/mv
however light does not have a mass so, it's not feasible to light(photons)

The more massive of a subject, it's visible wavelength is lower. So it will become undetectable.