## Photoelectric Effect vs. De Broglie

rachelle1K
Posts: 109
Joined: Sat Sep 07, 2019 12:16 am

### Photoelectric Effect vs. De Broglie

How do you know when do differentiate if you should use the speed of light equation or De Broglie?

Posts: 51
Joined: Fri Aug 30, 2019 12:17 am

### Re: Photoelectric Effect vs. De Broglie

speed of light can only be used for light/photons while de bregolie can be used with other types of particles

kevinolvera1j
Posts: 103
Joined: Fri Aug 02, 2019 12:15 am

### Re: Photoelectric Effect vs. De Broglie

The speed of light equation can only be used for Electromagnetic radiation since that equation, c=vλ is based on the propagation wave speed formula for values specific to light. The De Broglie equation is used for particles with momentum which means it is used for particles with mass, e.g. electrons, neutrons, and protons.

Micah3J
Posts: 100
Joined: Tue Oct 08, 2019 12:16 am

### Re: Photoelectric Effect vs. De Broglie

Do we use the De Broglie equation for the midterm review question 13a?

Justin Vayakone 1C
Posts: 110
Joined: Sat Sep 07, 2019 12:19 am

### Re: Photoelectric Effect vs. De Broglie

Micah3J wrote:Do we use the De Broglie equation for the midterm review question 13a?

Yes we do. We know this because we are using the wavelength of a potassium ion, which has mass. The speed of light equation on the other hand would be used for situations involving electromagnetic radiation, like light or UV rays. For 13a, the De Broglie equation is the right equation to use.

Micah3J
Posts: 100
Joined: Tue Oct 08, 2019 12:16 am

### Re: Photoelectric Effect vs. De Broglie

Justin Vayakone 4H wrote:
Micah3J wrote:Do we use the De Broglie equation for the midterm review question 13a?

Yes we do. We know this because we are using the wavelength of a potassium ion, which has mass. The speed of light equation on the other hand would be used for situations involving electromagnetic radiation, like light or UV rays. For 13a, the De Broglie equation is the right equation to use.

Thank you. Also for the mass of the potassium ion, I need the units in kgs right? For some reason I am not getting the same answer as the answer key

Justin Vayakone 1C
Posts: 110
Joined: Sat Sep 07, 2019 12:19 am

### Re: Photoelectric Effect vs. De Broglie

Micah3J wrote:
Justin Vayakone 4H wrote:
Micah3J wrote:Do we use the De Broglie equation for the midterm review question 13a?

Yes we do. We know this because we are using the wavelength of a potassium ion, which has mass. The speed of light equation on the other hand would be used for situations involving electromagnetic radiation, like light or UV rays. For 13a, the De Broglie equation is the right equation to use.

Thank you. Also for the mass of the potassium ion, I need the units in kgs right? For some reason I am not getting the same answer as the answer key

Yes the mass should be in kg because h (Planck's constant) is in J*s. . To cancel the kg from h, the mass will have to be kg.

Elizabeth Harty 1A
Posts: 125
Joined: Sat Jul 20, 2019 12:16 am

### Re: Photoelectric Effect vs. De Broglie

I thought that the units for joules had the second to the power of negative 2?

Lauren Lewis3L
Posts: 57
Joined: Wed Feb 20, 2019 12:16 am

### Re: Photoelectric Effect vs. De Broglie

Usually whenever I hear photon in a question or threshold energy, I immediately got to the photoelectric equations. These equations being the one for Kinetic Energy (1/2 m(v)^2). It is important to understand that velocity value is the only thing being squared and not the entire equation.