E=hcwavelength what is h

Photon energy can be expressed using any unit of energy such as the electronvolt eV or the Joule J. For short wavelength sources in the EUV to X-ray range, researchers often discuss photon energies in units of eV or keV for hard X-rays out of convenience. Thus, equation 1 above can be rewritten for photon energy in eV and wavelength in nm as:. Average power is related to flux and photon energy by:. For any given flux and wavelength in nm , equation 5 can be used to calculate the corresponding average power in m W.

Email Link. I understand what the constants are h Plank's , c speed of light , and wavelength, but I'm not entirely sure how to implement it. To be completely honest I'm getting all of these equations mixed up please explain them.

If you are asked to find energy you should use one of the other two equations, you can determine which to use based on the information given to you. No photoelectric electrons are emitted if the frequency of the light falls below this cutoff frequency f c. For many metal surfaces the frequency of blue light is greater than f c and the frequency of red light is less than f c.

If red light is shone on the surface, no electrons are emitted, no matter what the intensity of the light. If blue light is shone on the surface, electrons are emitted. The number of emitted electrons depends on the intensity of the light.

But even if the intensity is reduced to a very low value, electrons are still emitted, albeit at a very low rate. The photoelectric effect cannot be understood within the wave picture of light.

In the wave picture the energy of the light beam does not depend on the frequency, but only on the intensity, which is proportional to the square of the amplitude.

Einstein explained the photoelectric effect by postulating that an electron can only receive the large amount of energy necessary to escape the metal from the EM wave by absorbing a single photon.

In other words, all energy is a multiple of this constant multiplied by the frequency of the wave of light. Energy is therefore quantized, it is always a multiple of a single packet of energy. Wavelength l and Frequency n Relationships. Typical question 1 - What is the frequency of red light with a wavelength of