# Comparing Rayleigh & Tomson Scattering: What's the Difference?

• peterjaybee

#### peterjaybee

Would I be right in saying the difference between Rayleigh and Tomson scattering is that Tomson involves scattering off a free electron, whereas in Rayleigh the incident wave is scattered off a bound nucleus?

Alos are there any other differences in the two scattering processes?

Thanks

One final thing. Are both elastic scattering?

In the classical limit, Thomson scattering is treated as elastic scattering off a single "free" electron; If the electron atomic binding energy is B, and electron rest mass is m0c2, then B << hv << m0c2 for Thomson scattering. It is the classical limit of Compton scattering, which is inelastic. The energy of the scattered photon is given by
(1/hv') -(1/hv) = 1/[m0c2(1-cos{theta})]
which shows that the scattered photon hv' at theta=90 degrees is nearly exactly the same energy as the incident photon hv for UV and soft x-rays (hv ~ 1000 eV).

## 1. What is Rayleigh scattering?

Rayleigh scattering is a phenomenon that occurs when light interacts with small particles in the atmosphere, causing the light to change direction and scatter in all directions. It is named after the British physicist Lord Rayleigh who first described it in the late 19th century.

## 2. How is Thomson scattering different from Rayleigh scattering?

Thomson scattering is a similar phenomenon that occurs when light interacts with free electrons in a plasma, such as in the Sun's atmosphere. The main difference is that Thomson scattering involves the scattering of much larger particles (electrons) compared to Rayleigh scattering, which involves scattering of molecules in the atmosphere.

## 3. What causes the difference in scattering between Rayleigh and Thomson?

The key factor that determines the type of scattering is the size of the particles involved. In Rayleigh scattering, the particles (molecules) are much smaller than the wavelength of the light, resulting in a scattering pattern that is dependent on the wavelength. In Thomson scattering, the particles (electrons) are much larger than the wavelength of the light, resulting in a scattering pattern that is independent of the wavelength.

## 4. How do scientists use Rayleigh and Thomson scattering in their research?

Scientists use Rayleigh and Thomson scattering in a variety of ways, including studying the composition and properties of Earth's atmosphere and other planetary atmospheres. They also use these phenomena to study the behavior of plasma in the Sun and other astrophysical environments.

## 5. Can Rayleigh and Thomson scattering be observed in everyday life?

Yes, Rayleigh scattering can be observed in everyday life in the blue color of the sky and the reddening of the Sun at sunset. Thomson scattering can also be observed in everyday life in the form of auroras, which are caused by interactions between solar wind particles and Earth's magnetic field.