Physics 1

Physics 1

1. Universe & Solar System

   • Heliocentric model
     • The Sun is at the centre of the universe and everything else orbits around it.
     • Galileo observed 4 moons orbiting Jupiter which provided evidence supporting the heliocentric model.
       • This supported the heliocentric model because it disproved the geocentric model, showing not everything orbited the Earth. This was not enough to prove the heliocentric model however, as it didn't show everything orbiting the sun.
   • Geocentric model
     • The Earth is at the centre of the universe and everything else orbits around it.
   • Life Cycle of Stars
     • Massive star
       • Massive Star: Nebula Protostar Massive star Red Supergiant Supernova Black hole or neutron star
     • Average star
       • Average star: Nebula Gravity pull gas and dust togetherProtostarTemp. risesHydrogen fusesAverage star10 billion yearsNearly all the hydrogen fuses- star swells to a red giant because core isn't hot enough to withstand gravitational pullRed giantHeavier elements fuse1 billion years before throwing of a-Shell of gasWhite dwarfThe rest of the star is pulled together by gravity, collapsing to form a white dwarf.Black dwarf White dwarf eventually cools to a black dwarf.
     • Energy changes in stars
   • The Big Bang Theory
     • The universe began 13.5 billion years ago. It expanded outwards from a tiny point of concentrated energy and is still expanding today.
     • CMB
       • Cosmic Microwave Background Radiation: Supports only the Big Bang Theory. Microwaves thought to be the detectable remenants of gamma radiation released in the Big Bang.
   • The Steady State Theory
     • The universe has always existed and is expanding. New matter is continually being created.
     • Red-shift
       • Supports both the Big Bang Theory and the Steady State Theory. Red-shift is a change in the wavelength of light. All galaxies show red-shift, suggesting the universe is expanding. Some galaxies show greater red-shift than others, these galaxies are moving away from Earth faster.

2. EM Spectrum

   • Radiowaves
     • Uses: Broadcasting, communications and satellite transmissions.
   • Microwaves
     • Uses: Cooking, communications and satellite transmissions. Dangers: Internal heating of body cells.
   • Infrared
     • Uses: Cooking, thermal imaging, remote controls and security systems. Dangers: Skin burns
     • Herschel
       • Sir Frederick William Herschel decided to investigate the temperature of each colour of the spectrum produced when light is passed through a prism. He noticed the temperature increased moving from the violet to the red end of the spectrum. He also observed that the region just beyond the end of the red spectrum was a higher temperature than the red itself. What he observed here was infrared radiation.
   • Visible light
     • Uses: Vision, photography and illumination.
   • Ultraviolet
     • Uses: Detecting forged bank notes, fluorescent lamps, security marking and disinfecting water. Dangers: Damages skin cells and eye cells, leading to skin cancer and eye conditions.
     • Ritter
       • Johann Ritter heard about Herschel's discovery and decided to see if invisible light existed on the violet end of the spectrum too. Silver chloride turns black in sunlight; it turns black quicker in blue light closer to the violet end of the spectrum. He then split light using a prism and observed that when exposed to the region just beyond the violet end of the spectrum, silver chloride turned black even quicker than when exposed to the visible light.
   • X-rays
     • Uses: Observing the internal structure of objects, airport security and medical X-rays. Dangers: Ionising radiation that can cause cell mutations leading to cancer.
   • Gamma rays
     • Uses: Sterilising food and medical equipment, and detecting and treating cancer. Dangers: Ionising radiation that can cause cell mutation leading to cancer.

3. Energy

   • Conservation of energy