Physics- P1 Topic 1, 2 & 3

Physics- P1 Topic 1, 2 & 3

1. Thoughts on the Solar System

   • The ancient Greeks believed in the Geocentric model about the solar system, they thought that the sun and the planets all orbited the earth. The heliocentric model later replaced what astronomers thought of the solar system. In this idea about the design of the solar system it says that the sun is the centre of the universe rather than the earth and is the design that is widely accepted today.

2. Waves

   • Wavelength: The distance from one peak of a wave to the the next Frequency: How many complete waves there are passing a certain point a second  Amplitude: The height of the wave from the mid-line to the peak Speed: How fast it goes Speed=FrequencyxWavelength WaveSpeed=Distance/Time Tranverse waves: The vibrations are at 90 degrees to the direction of travel Longitudinal waves: The vibrations along the waves are in the same direction as the wave is travelling

3. Reflection and Refraction

   • When a wave hits a boundary between one medium and another some of its energy is reflected. It is reflected because of the change in density between the two mediums. They can also be refracted as when the wave goes into a denser medium it changes the speed, this causing the wave to change direction towards the normal, when it then leaves the new medium it will change direction back to the original as it has been refracted back to the original direction

4. Lenses

   • A converging lense bulges outwards, causing parallel rays to converge together to a focus. It has a focal point both in front and behind the lens and this is where the rays going through the lens all meet.

5. Simple and Reflecting Telescopes

   • A refractive telescope is made up of a objective lens and an eyepiece lens, the objective lens converges the rays of the object image to form a real image at the focal point. The rays of light from the real image then enter the eyepiece lens and spreads out the rays which means that the image takes up more of the retina and making the image seem bigger. A reflective telescope uses concave mirrors and a converging lens. A concave mirror works as when an incident ray parallel to the axis will pass through a focal point when it's reflected and a incident ray passing through a focal point will be parallel to the axis when it's reflected.  The concave mirror collects the parallel rays of light from and object in space and the larger mirror reflects the light onto a smaller mirror in front of the first mirror's focal point . The smaller mirror then reflects the light through a hole in the centre of the large collecting mirror and a real image is formed behind it and a converging eyepiece lens is used to magnify this.

6. Electromagnetic Waves

   • There are seven types of EM waves: Radio Waves Mircro-Waves Infrared Visible Light Ultra-Violet X-Rays Gamma Rays They are all tranverse waves and travel at the same speed in a vacuum Before the discovery of infrared radiation in 1800 the only part of the EM spectrum we were aware of was visible light. But in 1800 Herschel was testing the spectrum of colours when white light is put through a prism. He tested the temperature in each of the colours and he noticed that they increased from violet to red, he decided to measure the temperature just outside the red part of the spectrum and discovered that this was even hotter, he had discovered infrared radiation. A year later a scientist named Ritter carried out an experiment to see if there was anything else on the other side of the spectrum. He knew that silver chloride changed from white to black when exposed to light and therefore tested how long it took silver chloride coated strips to change from white to black when exposed to different colours of light. The strips changed colour quickest at the blue end of the spectrum. He then placed a strip just outside the violet part of the spectrum, this showed the quickest change of colour out of all of them, ultra-violet light.

7. The Dangers of EM Radiation

   • The effects of EM radiation on humans depends on the frequency of the waves because the frequency determines the energy of the wave. Micro-waves heat human body cells and have been linked causing brain tumours Infra-red also heats cells and have much more energy than micro-wave radiation and have been linked to skin burns Ultra-violet can cause skin cancer which can later become skin cancer and cause eye damage Gamma/X-ray they cause cell mutation and cancer as they penetrate the body more and ionise cells within

8. Radiowaves and Microwaves

9. Infrared Radiation

   • Infrared Radiation is given out by all hot objects, for this reason IR can be used to monitor temperature. IR is detected using night-vision equipment which changes the IR into an electrical signal which is then displayed on a screen and the hotter the object the brighter it appears on screen. Optical fibres use infrared radiation to carry data over long distances. Infrared is used in many things around the home, such as:  Cooking appliances e.g toasters or grills Remote controls for DVDs or TVs Transmitting information between mobile or computers over short distances

10. Visible Light, UV and X-Rays

    • When light enters the eye it gets refracted through the lens and focused onto the retina at the back of the eye which then sends messages to the brain.  Ultraviolet Radiation is used to detect forged bank notes because fluorescence is a property of certain chemicals that absorbs ultra-violet and emits visible light. The banks print special markings in fluorescent ink onto the bank notes which allows them to detect forgeries as under UV light the real notes will display the markings and the forged ones will not. X-Rays are used to looks inside of objects in places like hospitals so that we can easily see through the thin materials but not the denser materials such as bone or metal.

11. Gamma Rays and Ionising Radiation

12. The Solar System

    • All planets orbit around a star and often have moons orbiting around them. The planets in our solo system vary in size, climate and orbit which all effect the conditions that are present on the planet. For a manned spacecraft to reach the moon it would take 3 days, to get to mars it would take 9 months and to get to neptune it would take 12 years. Our sun is in the milky way galaxy and is one of many billions of stars in the galaxy. There are billions of galaxies in the universe however no one is sure how big the universe actually is..

13. Looking into Space

    • Scientists often use telescopes to look into space however when we look into space from the surface of the earth the atmosphere absorbs some of the light and so to get the clearest images we need to look at them from in the atmosphere so that the light isn't absorbed and so the images that are received are clearer.  The earliest telescopes that we used were optical telescopes which detect visible light that are used to look at objects close by and in other nearby galaxies. We later started to use telescopes that detect all parts of the EM spectrum. For example we use x-ray telescopes to observe high temperature events in space such as exploding stars. Another example is radio telescopes which we use to monitor cosmic microwave background radiation which tells us about the origins of the universe.

14. Looking for signs of life

    • Many scientists want to find out if there's life out there however the distances across space is massive and so it is hard to discover if and where other creatures are.  Scientists are always sending radio, TV and radar into space for any aliens out there to detect. We are also constantly searching for narrow bands of radio wavelengths coming to earth from outer space. We also use spacecraft to try and collect evidence of life, they carry equipment that continuously record data about temperature and the conditions to see if it could sustain life.

15. Space and Spectometry

    • A spectrometer is a tool used to analyse the light given out by stars and galaxies. The telescopes direct a beam of light into the spectrometer which defracts the light and splits it into a spectrum which scientists can analyse to find out information about the universe.

16. Life Cycle of Stars

    • Stars initially form from clouds of dust and gas called nebulas. The force of gravity makes the gas and dust spiral in together , the gravitational energy is converted into heat energy and so the temperature rises. When the temperature gets high enough the hydrogen nuclei undergo thermal nuclear fission to form helium nuclei and give out massive amounts of energy and the star is born. It immediately enters a long stable period where the heat created by the nuclear fusion provides an outward pressure to balance the force of gravity pulling everything inwards. This period is known as the main sequence star. Eventually the hydrogen in the core of the star begins to run out and the star swells into a red giant star. If the star is small to medium then it will become unstable and eject its outer layer which creates a planetary nebula and then the rest turns into a white dwarf which cools down and then eventually disappears.  However if it was a big star they would start to glow brightly and then undergo more fusion and form heavier elements and explode into a supernova and it will either become a neutron star which is very dense or it will form a black hole if it is big enough.

17. The Origins of the Universe

    • Scientists believe that the universe was started with the big bang where all the matter and energy in the universe was compressed into a very small space which then exploded. Red shift is evidence for this theory because if something is moving away from you it is tinted slightly red but if it is moving towards you then it is tinted blue, some planets are tinted red showing that they are moving away indicating that their was an explosion.