OCR Physics A - G485: Fields, Particles & Frontiers of Physics - June 2012

•

Incoming X-ray photon collides with an orbital electron.

•

This is an inelastic collision, and the photon transfers energy to the electron.

•

The electron is ejected and the photon is scattered (has lower energy).

•

This requires a higher voltage system that is required for the photoelectric effect.

•

The material of the star is acted upon by two forces, Gravity and Nuclear Reaction Forces.

•

Hydrogen in converted into Helium.

•

Rate of fusion eventually decreases in the core of the Sun as the Hydrogen is used up and converted to Helium.

•

The core contracts.

•

The loss of potential energy ion contraction results in increase in kinetic energy and so the temperature and pressure in the core increases.

•

Helium nuclei fuse to make heavier elements.

•

Radiation pressure is now greater and so outer parts of star expand.

•

There's greater luminocity because of an increased surface area and the surface temperature is less due to increase in potential energy - Red Giant.

•

As fusion stops the stability of the Sun decreases. The outer layer is lost.

•

The remains of the star collapse under its own gravity and becomes a white dwarf.

•

Regions of dust and gas with different densities

•

The regions with higher densities have more gravitational pull towards them, so over time they become even more dense.

•

the density increases even more to form a stellar nebula

•

density continuous to increase, resulting in more collisions between atoms, so PE decreases and KE & temperature both increase.

•

the process is repeated until a protostar is formed (a massive core that glows)

•

the protostar attracts even more material and becomes large enough to emit light

•

the core has a high density, pressure and temperature; allowing for the fusion of hydrogen and helium