frequency and speed

[asannajust_1J]

Why does the speed of radiation decrease when the frequency decreases?

[AVerma_F19]

The speed of radiation does not decrease with increased frequency. c = Frequency*Wavelength, where c is the speed of light (3*10^8m/s). Since c is constant, frequency and wavelength are inversely proportional. This means that if frequency goes up, wavelength will go down, and vice versa.

[asannajust_1J]

But if kinetic energy is = energy of a photon - threshold energy, then wouldn't the velocity of the photon be proportional to the frequency.

[asannajust_1J]

since 1/2mv^2= hf - threshold?

[AVerma_F19]

Using the equation you mentioned (KE(electron) = E(photon)-Threshold Energy), the speed of the photon is not in question. Photons (and all radiation) will travel at 3*10^8 m/s. However, depending on how much energy the photon has, the KE of the electron (not radiation) will change via velocity (since mass of e- stays the same).

[asannajust_1J]

If the electromagnetic radiation is light, then it can be thought of as an EM wave. So since E=hv, the energy per photon would be proportional to the frequency not necessarily the speed. Correct?

[Keerthana Sivathasan 2E]

Speed of radiation does not decrease when frequency decreases because it is a constant. Using the formula c=v*wavelength where v is frequency and c is speed, if v increases, then wavelength will decrease in order to maintain the same c. The variable c can't change because it is a constant.

[Osvaldo SanchezF -1H]

Speed should not be in question when you are dealing with these type of equations. It is rather the strength of the radiation that changes itself which is proportional to the wavelength. The speed will always be the speed of light which is 3*10^8. So if frequency increases wavelength decreases and vice versa. This all relates back to the amount of energy that you are putting off.