GCSE Physics Edexcel P1 Topic 3

These are revision notes I made myself. I got A* in the Physics GCSE exam and 76 UMS in the P1 exam using only these notes.

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P1 Topic 3: Waves and the Universe
Ancient astronomers made detailed observations of the positions of the stars using the naked eye. Using a
telescope, Galileo Galilei discovered that the Milky Way and some nebulae (Latin word for clouds) were
actually groups of stars. He also suggested that stars and other sun were at difference distances from the
Earth, contradicting the idea that they made a fixed shell around the Earth.
With greater magnifications of telescopes, more discoveries were made about the Solar System and the
stars. We now know that there are eight planets, few dwarf planets, many moons and smaller bodies like
asteroids in our solar system.
The Sun is just one of millions of stars that make up our galaxy ­ the Milky Way. There are billions of galaxies
in the Universe which make up the Universe.
Telescopes have also been used by astronomers to make observations to allow them to figure out the size
of planets, stars and galaxies and the distances between them.
Object Diameter (Km) Distance from Earth (km)
Earth 13,000 N/A
Moon 3, 500 384,000
Sun 1,400,000 150,000,000
Neptune 50,000 4,500,000,000
Proxima Centauri 100,000 4.0 x 1013
Milky Way 1.0 x 1018 N/A
Andromeda 1.4 x 108 2.5 x 1019
Most distant galaxy observed Too far to measure 1.2 x 1023
A spectrometer is a tool used to analyse the light given out by stars and galaxies.
Light from the Sun is a mixture of different colours forming a spectrum. However, gases in the Sun's and
Earth's atmosphere absorb some of the light, causing dark bands to form on the Sun's spectrum. The patterns
are called the absorption spectra.
Absorption spectra can be used to work out what the stars and galaxies are made of ­ each element has its
own particular absorption spectrum.
Some spectra have bright lines ­ these are emission spectra. The lines are caused by extra light being
emitted at those wavelengths. Emission spectra can also be used to work out what something is made of.
Visible light is a mixture of light of different frequencies and wavelengths. These wavelengths can be split up
using a prism, or by something with a lot of fine lines such as a DVD or CD. A device that can split up
wavelengths of light is called a spectrometer.
Exploring the Universe
Early telescopes let people see objects that emitted visible light. Photography vastly increased the amount
of data that could be gathered with the telescopes. Objects too far away to see can be recorded as a
photograph by pointing the telescope in its direction for several hours.
Modern telescopes use digital cameras to record images and computers are used to analyse the images.
Spectrometers can be attached to telescopes to analyse the different wavelengths of light given off stars
and galaxies.
Most objects that are observed give off energy in all parts of the electromagnetic spectrum. As a result
modern telescopes can be made to detect these different kinds of radiation, thus showing us things which
could not be detected with visible light. For example, X-rays can detect objects in space that block visible

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Visible light only occupies a small part of the electromagnetic spectrum so only using that means we'll only
discover an equally small part of the universe.
Telescopes in Space
The Hubble Space Telescope has been orbit around the Earth since 1990. It can produce very sharp and clear
images of stars and galaxies as it is above the atmosphere.…read more

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Telescopes are improving all the time to give us better resolution and can gather more light so even the
faintest objects can be seen.
Discovering galaxies is important to help scientists learn more about their life cycle. Some pictures taken by
the Hubble Space telescope show galaxies at different stages of their life. These images are used to help
scientists learn more about how galaxies are formed and how they evolve.
Modern telescopes work alongside computers.…read more

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After about 10 billion years, the hydrogen in the core begins to run out and the star then swells into a red
giant (it becomes red as the surface cools). It expands as the core of the star is not hot enough to withstand
the gravity and collapses, expelling its outer layers to form a larger star.
5. The star will remain a red giant for a billion years. Other fusion reactions occur in the meantime.…read more

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Big Bang theory.
The theory states that huge amounts of radiation were released at the beginning of the Universe and is still
detectable as microwave radiation today (it decreased in frequency over time).
Red-shift supports both theories as both say the Universe is expanding. However, CMB radiation only
supports the Big Bang theory and the Steady State theory cannot explain it. As there is more evidence for it,
the Big Bang theory is the one that is most accepted by astronomers today.…read more



thxs:D very useful

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