## When to use DeBroglie or Ek equation

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

Danielle Sumilang - 1F
Posts: 31
Joined: Fri Apr 06, 2018 11:05 am

### When to use DeBroglie or Ek equation

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)?

ErinKim1I
Posts: 31
Joined: Fri Apr 06, 2018 11:03 am

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

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.

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

You use DeBrogile when given a mass value.

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

For example, light doesn't have any mass that is why we are unable to use DeBroglie's equation to find E.

Celeste Martinez 1K
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### Re: When to use DeBroglie or Ek equation

On my notes, I have written that the DeBroglie equation does not apply to light since light doesn't contain mass.

Neha Divi 1K
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### Re: When to use DeBroglie or Ek equation

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.

Endri Dis 1J
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### Re: When to use DeBroglie or Ek equation

If we have to use the DeBroglie is it certain that the mass will always be given for a problem?

304984981
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Joined: Fri Apr 06, 2018 11:05 am

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

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.