How do red and blue light differ from one another?

Question

is it intensity...different numbers of photons in them. differ in duration..

Answer 1

Red light and blue light are both light, which means that both of them are made up of photons, which means that they are all energy. However, light behaves like a wave as well, this is the wave-particle duality of light.

Waves have wavelengths and frequencies. Since V=Fλ, where v is velocity of light (3 mil m/s), the different colours of light depend on the frequency and wavelength. Red light has a higher wavelength and lower frequency, approximately 700nm, while blue light has a lower wavelength, approximately 400nm.

Answer 2

Red photons have a longer wavelength than blue photons. That is, the crests of the electromagnetic waves of red light are farther apart than in in blue light. This also means that red light has less energy than blue light per photon.

Answer 3

Wavelenght.

Answer 4

The first thing you should know about light is that it is made of tiny packets of energy, called photons [I know you already know this]. By saying this, we mean energy is QUANTISED, where you can't have a fraction of a multiple of the energy of an individual photon.

Light exhibits both wave and particle properties. It exhibits 'wave-particle duality', and this is one of the underlying principles of the modern quantum theory.

The basic wave equation is

v = fλ,

velocity = frequency x wavelength.

When you talk about light, you can say

c = fλ,

where c is the speed of light, approximately 3 x 10^8 m/s. This is about 900 000 times the speed of sound, which is about 330 m/s.

However, you can also speak of light in terms of quantised photons, where the energy of each photon is given by the equation

E = hf

where E = energy, h = planck's constant, f = frequency [in Hz].

Since f = c/λ,

You get E = hc/λ.

energy = planck's constant x speed of light / wavelength.

Heard of the photoelectric effect? It is a phenomenon explained by Einstein that won him the Nobel Prize in Physics in 1905.

Imagine you have a piece of metal. If you were to shine light of different wavelengths at it, sometimes electrons would be ejected from it. This alone is not remarkable. But variations to the experiment start getting a little creepy.

When light below a certain frequency was used, no electrons were ejected. After a while, electrons were ejected. When the frequency was further increased, the electron number did not increase, only the speed of the electrons.

On the other hand, when light of a single frequency was varied in intensity, the number of electrons ejected increased.

Why is this so?

First, you should know about Bohr's atomic model. It explains that the atom is made up of electron orbits around the nucleus, where the amount of energy at each energy level is defined by the equation:

E = Rh(1/n^2)

where Rh is Rydberg's constant, n = the energy level.[the one closest to the nucleus is 1, next is 2, and so on.]

When light is shone upon the metal, an electron absorbs the photon, and gains energy. Since it can no longer stay within that orbit, it will jump to a higher energy level [further away from the nucleus]. But what goes up probably will come down, so the electron de-excites and returns to its original energy level. It loses the excess energy by releasing a photon corresponding to the equation

E = Rh(1/Nf^2 - 1/ni^2)

where Rh is Rydberg's equation, nf is the final energy level, ni is the initial energy level.

However, sometimes the energy from the photon is enough to release the electron from the atom altogether. This is called 'ionisation potential'.

From the equations above, you can see that energy is related only to the frequency of the light. So after a while, the frequency of the light shone on the metal is enough to eject electrons from the metal.

After a while, the frequency increase gives the electrons more and more energy, so it is ejected at higher speeds.

Intensity of light depends on the number of photons present in the stream. So when light is brighter, there are more photons. When it is shone on the metal, there will be more photons to eject more electrons. Therefore, when there is a higher intensity [beyond a certain frequency], there will be more electrons ejected.

So that's the photoelectric effect, and it hopefully has helped you to understand the differences in light when you vary the frequency, wavelength and so on.

Finally, I assume you meant 'period', when you said 'duration'. Well, period is simply the amount of time light takes to complete a wavelength. This is inversely proportional to frequency. ie. frequency = 1/period, period = 1/frequency.

Hope this helped!

Cheers :D

Answer 5

Blue light has a shorter wavelength than red light.  Blue light has a wavelength of 475 nm (nanometers).  Red light has a wavelength of 650 nm.