## Relationship between Speed and Frequency

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

### Relationship between Speed and Frequency

On homework problem 1A #3, why does speed not also decrease when frequency decreases? I combined equations to obtain $\frac{c}{f}=\frac{h}{mv}$
, with f being frequency and v as velocity. Is it incorrect to combine the de broglie equation with speed of light equation? If so, what is the relationship between speed and frequency as terms of radiation?

sarahsalama2E
Posts: 164
Joined: Fri Aug 30, 2019 12:16 am

### Re: Relationship between Speed on Frequency

Remember that the equation is c=wavelength x (v) ---> meaning that v stands for frequency NOT velocity. Speed and frequency are not related in a directly proportional manner. Increasing the frequency simply means increasing the cycles per second that are happening of the given wave, and decreasing the frequency would mean decreasing the cycles per second that are happening of the given wave. This does NOT mean you are changing the actual speed of the wave. Hope that helps.

EvanWang
Posts: 101
Joined: Sat Sep 07, 2019 12:16 am

### Re: Relationship between Speed and Frequency

We assume the speed of light to be constant, so any changes in frequency won't impact the speed of the wave. Also, $\frac{h}{mv}$ only applies to particles with resting mass like electrons, not electromagnetic radiation.

Kassidy Ford 1I
Posts: 103
Joined: Sat Aug 17, 2019 12:16 am
Been upvoted: 1 time

### Re: Relationship between Speed and Frequency

as the person above said, de broglies equation can only be used for particles with a resting mass. Since light does not have a resting mass, the equations are not interchangeable.