**Compton Effect:**

The effect described in the question is known as the Compton effect. It refers to the scattering of X-rays by matter, resulting in a change in their wavelength. This effect was discovered by Arthur H. Compton in 1923 and played a crucial role in confirming the particle nature of X-rays.

**Explanation:**

When X-rays are incident on a lighter element, such as hydrogen or helium, they interact with the electrons present in the atom. The Compton effect occurs due to the phenomenon of inelastic scattering, where the incident X-ray transfers some of its energy and momentum to the electron it interacts with.

Here is a detailed explanation of the Compton effect:

1. **Incident X-ray**: A monochromatic X-ray beam is directed towards a lighter element.

2. **Interaction with electrons**: As the X-rays interact with the electrons in the atom, they collide and transfer some of their energy and momentum to the electron.

3. **Scattered X-ray**: The X-ray that emerges from the interaction is called the scattered X-ray. Due to the transfer of energy and momentum, the scattered X-ray has a longer wavelength (lower frequency) compared to the incident X-ray.

4. **Change in wavelength**: The change in wavelength of the scattered X-ray can be explained by the conservation of energy and momentum. The energy and momentum transferred to the electron cause it to recoil, resulting in a shift in the wavelength of the scattered X-ray.

5. **Wavelength shift**: The amount of wavelength shift depends on the angle at which the scattered X-ray is detected and the energy of the incident X-ray. This shift can be quantitatively described by Compton's equation: Δλ = h / (mec) * (1 - cosθ), where Δλ is the change in wavelength, h is the Planck's constant, me is the electron mass, c is the speed of light, and θ is the scattering angle.

6. **Detection**: The scattered X-rays can be detected and analyzed to determine the change in wavelength, which provides valuable information about the nature of the interaction and the properties of the atom.

**Conclusion:**

In conclusion, the effect described in the question is known as the Compton effect. It refers to the scattering of X-rays by matter, resulting in a change in their wavelength. The scattered X-rays have wavelengths larger than the incident rays due to the transfer of energy and momentum from the incident X-ray to the electron it interacts with. This effect played a significant role in confirming the particle nature of X-rays and has important applications in various fields, including medicine and materials science.

Compton effect