De Broglie Equation v. Speed of Light Equation


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Madisen Brown -1C
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De Broglie Equation v. Speed of Light Equation

Postby Madisen Brown -1C » Fri Oct 23, 2020 11:58 am

I'm having difficulty comprehending when to use De Broglie's equation to find the wavelength and when to use the speed of light equation to find the wavelength. Are there certain conditions for the different equations that I should be aware of? Or any given information/keywords used in a problem that would be an indicator?

Pranav Daggubati 3C
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Re: De Broglie Equation v. Speed of Light Equation

Postby Pranav Daggubati 3C » Fri Oct 23, 2020 12:01 pm

generally, you would use the speed of light equation of electromagnetic traditions, light, and the de Broglie equation for things with mass, such as electrons and basketballs

Anna Martin 2l
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Re: De Broglie Equation v. Speed of Light Equation

Postby Anna Martin 2l » Fri Oct 23, 2020 12:02 pm

When you are finding the wavelength of something that has mass is when you should be using de Broglie, like an electron or an object. Therefore, you cannot use this to calculate the wavelength of photons because they have no mass and must use the other equation to find the wavelength of light.

Chanel Mao 3D
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Re: De Broglie Equation v. Speed of Light Equation

Postby Chanel Mao 3D » Fri Oct 23, 2020 12:03 pm

Hi! The speed of light equations are used when you want to find the wavelength/frequency of a photon, so you can't use it for other objects. You can instead use DeBroglie's equation to find the wavelength! Also, sometimes the question asks if an object's wavelength is detectable/not detectable, which I typically associate with DeBroglie's equation. Hope this helped!

Madisen Brown -1C
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Re: De Broglie Equation v. Speed of Light Equation

Postby Madisen Brown -1C » Fri Oct 23, 2020 2:05 pm

Anna Martin 2l wrote:When you are finding the wavelength of something that has mass is when you should be using de Broglie, like an electron or an object. Therefore, you cannot use this to calculate the wavelength of photons because they have no mass and must use the other equation to find the wavelength of light.

That makes sense! Thank you

Madisen Brown -1C
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Re: De Broglie Equation v. Speed of Light Equation

Postby Madisen Brown -1C » Fri Oct 23, 2020 2:06 pm

Chanel Mao 2F wrote:Hi! The speed of light equations are used when you want to find the wavelength/frequency of a photon, so you can't use it for other objects. You can instead use DeBroglie's equation to find the wavelength! Also, sometimes the question asks if an object's wavelength is detectable/not detectable, which I typically associate with DeBroglie's equation. Hope this helped!

That's a good indicator! Thanks for your help.

Brandon Le 3C
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Re: De Broglie Equation v. Speed of Light Equation

Postby Brandon Le 3C » Fri Oct 23, 2020 2:12 pm

You will generally need to use de Broglie's Equation when it comes to things with mass, velocity, or momentum, like an electron or other particle. Things like photons don't have mass, which is when you would use the speed of light equation.

Jason_John_2F
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Re: De Broglie Equation v. Speed of Light Equation

Postby Jason_John_2F » Fri Oct 23, 2020 2:21 pm

Yes, put simply, De Broglie Equation is used on things with mass while Speed of Light is used on photons which are massless.

Nathan Chu 3H
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Re: De Broglie Equation v. Speed of Light Equation

Postby Nathan Chu 3H » Sat Oct 24, 2020 10:46 am

The de Broglie equation is only applicable for objects with mass, as the equation involved momentum which is mass * velocity. The speed of light equation only applies to light, such as the emission from atomic spectroscopy or electromagnetic radiation.

Eric Cruz 2G
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Re: De Broglie Equation v. Speed of Light Equation

Postby Eric Cruz 2G » Sat Oct 24, 2020 10:55 pm

Hi, I too became confused as to when to use the speed of light and electromagnetic equations such c=lamda *v, E=hc/lamda, E=hv and went to use the De Broglie Equation (lamda= h/4pi). However, I have come to the realization that the speed of light equation is for photons which are in the electromagnetic spectrum. Photons do not have mass, so mass is not relevant and is why we do not see mass in any of the equations. However for objects that are not photons such as electrons, neutrons, protons, and even cars, (anything with velocity and mass) mass and velocity are important aspects of it. De Broglie incorporates mass and velocity and therefore is the better equation to use to find wavelength. However, if mass and velocity are not relevant such as photon, use the speed of light equation.

Sreeram Kurada 3H
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Re: De Broglie Equation v. Speed of Light Equation

Postby Sreeram Kurada 3H » Sat Oct 24, 2020 11:00 pm

Debrogile's equation is used to find the wavelength and momentum of small objects such as electrons, protons, and neutrons, while the speed of light equation is used to find the wavelength and frequency of light.

Nina Tartibi 1F
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Re: De Broglie Equation v. Speed of Light Equation

Postby Nina Tartibi 1F » Sat Oct 24, 2020 11:06 pm

Since photons have no mass, the speed of light equation can be used to find wavelength of photons. However, when dealing with objects such as cars, baseballs, or electrons that involve mass, you'd use DeBroglie's equation. The wavelength of small objects are detectable such as electrons and neutrons, but not detectable for cars, balls, etc.

Katelyn_Ortega_1D
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Re: De Broglie Equation v. Speed of Light Equation

Postby Katelyn_Ortega_1D » Sun Oct 25, 2020 12:19 am

To find wave length, you use the De Brogile equation

Xavier Herrera 3H
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Re: De Broglie Equation v. Speed of Light Equation

Postby Xavier Herrera 3H » Sun Oct 25, 2020 11:45 am

The de Broglie equation gives you the wavelength and momentum of something with mass. Since photons don't have mass, you would have to use the speed of light equations.

Sydney Jensen 3L
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Re: De Broglie Equation v. Speed of Light Equation

Postby Sydney Jensen 3L » Sun Oct 25, 2020 10:07 pm

The equations for the speed of light refer to protons, so any other object that has mass can have the wavelength or frequency calculated by utilizing the De Broglie equation.


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