## When to use DeBroglie Equation

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

Ally Huang- 1F
Posts: 103
Joined: Thu Jul 25, 2019 12:16 am

### When to use DeBroglie Equation

Do you only use the DeBroglie Equation to solve for wavelength of an electron or can you use this equation to solve for the wavelength of light too? The light equation was part of the derivation for the equation so I am not sure if the wavelength of light can also be found from this equation.

005391550
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am

### Re: When to use DeBroglie Equation

I think you only use it for the wavelength of particles with momentum. if you wanted to solve the wavelength of light, this equation would require you to know the momentum. the wavelength of light can be found by using c = wavelength*frequency instead.

Kendall 3H
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Joined: Wed Sep 18, 2019 12:18 am

### Re: When to use DeBroglie Equation

You can use DeBroglie's equation to find the wavelength of anything but light because light does not have mass.

Posts: 87
Joined: Sat Aug 24, 2019 12:15 am

### Re: When to use DeBroglie Equation

We would use the Debroglie Equation for anything that has mass. Because an electron has a mass we would use the Debroglie. In contrast, photons are practically massless objects and therefore we do not have to worry about representing their mass and can use c= ƛv. Hope this helps!

KBELTRAMI_1E
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Joined: Sat Jul 20, 2019 12:17 am

### Re: When to use DeBroglie Equation

Doesn't it have to do with when there is a quantifiable mass given and there are wave-like and particle-like properties both?

Khushboo_3D
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Joined: Wed Sep 18, 2019 12:19 am

### Re: When to use DeBroglie Equation

You can use De Broglie's equation to find the wavelength of anything hat has a rest mass. For example, an electron has a rest mass. However, light does not have a rest mass and so you cannot use De Broglie's equation to find its wavelength eve though the derivation we did in class involved light.

Eileen Si 1G
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Joined: Fri Aug 30, 2019 12:17 am

### Re: When to use DeBroglie Equation

You cannot use the DeBroglie Equation for light, but for particles that have momentum or wavelike properties (a wavelength).

AmyL_3L
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Joined: Fri Aug 09, 2019 12:17 am

### Re: When to use DeBroglie Equation

You can use De Broglie's equation when you are trying to find the wavelength of particles that have mass. However, it cannot be used to measure light.

Sanjana Borle 2K
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Joined: Fri Aug 09, 2019 12:15 am

### Re: When to use DeBroglie Equation

You can't use the DeBroglie equation in terms of light because the light equation involves the constant C which is the speed of light, so the EM equations cannot be used for any particle either (doesn't work either way). The DeBroglie equation works only for particles which have wavelike properties.

KTran 1I
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Joined: Fri Aug 30, 2019 12:15 am

### Re: When to use DeBroglie Equation

As stated in the previous replies, the DeBroglie equation can only be used for objects that have rest mass, which does not apply to light. The equations λν = c or the E = hν are applicable to light.

Harry Zhang 1B
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Joined: Sat Sep 14, 2019 12:16 am

### Re: When to use DeBroglie Equation

The De Broglie equation can be used with any object as long as you have the p=momentum of the object, therefore theoretically you can also use it with light because although photons don't have mass, they still have momentum, but in order to this you have to be given its momentum since you cannot calculate it. Therefore the easier way to calculate the wavelength of light is to just use the formula lambda*frequency=c. However, for objects other than light, you can only use the De Broglie equation since the equation lambda*frequency=c only applies to electromagnetic radiation.

Maggie Eberhardt - 2H
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Joined: Sat Jul 20, 2019 12:16 am

### Re: When to use DeBroglie Equation

KTran 1I wrote:As stated in the previous replies, the DeBroglie equation can only be used for objects that have rest mass, which does not apply to light. The equations λν = c or the E = hν are applicable to light.

Is light the only thing without rest mass? And I'm also confused as to how rest mass apply to electron's wavelike properties

alexfwang3g
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Joined: Thu Jul 11, 2019 12:16 am

### Re: When to use DeBroglie Equation

You can use this equation to find the variables for everything but light as light's photons do not have a measurable mass.

Maika Ngoie 1B
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Joined: Fri Aug 02, 2019 12:16 am

### Re: When to use DeBroglie Equation

De Broglie's equation can be used to calculate the energy of anything with measurable wavelength properties OTHER THAN light. Typically speaking, a DeBroglie wavelength less than 10^-15 does not have detectable wavelength properties. Hope this helps!

Keerthana Sivathasan 2E
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Joined: Wed Sep 18, 2019 12:22 am

### Re: When to use DeBroglie Equation

DeBroglie is used for all moving particles and is a link between matter having wave properties and vice versa. The higher the energy, the lower the DeBroglie wavelength. All the moving particles must have a "matter wave", which is a probability function, associated with them.

Darren Nguyen 1F
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### Re: When to use DeBroglie Equation

Not light because it doesn't have mass

KTran 1I
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Joined: Fri Aug 30, 2019 12:15 am

### Re: When to use DeBroglie Equation

Maggie Eberhardt - 3B wrote:
KTran 1I wrote:As stated in the previous replies, the DeBroglie equation can only be used for objects that have rest mass, which does not apply to light. The equations λν = c or the E = hν are applicable to light.

Is light the only thing without rest mass? And I'm also confused as to how rest mass apply to electron's wavelike properties

Light is not the only object that does not have mass, but I think that the other objects would be out of the context of this class. In terms of how the rest mass of an electron connects to wavelike properties is because since it has a mass, we would use the Debroglie equation since one of the conditions of this equation is for the object to have rest mass.