P1 - Universal physics

1. P1 - Universal physics A Massawe

2. How science works • Independent variable – • Dependent variable - • Controlvariable – • Hypothesis – • Secondary evidence - this is the quantity that you change this is what you measure this is what must be kept the same to ensure a fair test an idea based on observations without experimental evidence data collected by someone else, you may find it in a book or on the internet A Massawe

3. How do scientist validate results? 1. they repeat experiment results2. they publish their findings in scientific journals 3. conference presentation 4. peer review/other scientists investigate the same findings. A Massawe

4. Models of the solar system • Geocentric model(Ptolemy) - the earth at the centre and all the planets and the sun orbiting around it • Heliocentric model(Nicolaus Copernicus) - the sun at the centre of the universe, based on observations with the telescope A Massawe

5. Observing the universe Optical telescopes • observe visible light from space • The Hubble telescope is an optical telescope in space • Optical telescopes on the ground have some disadvantages: 1. 2. they can only be used at night they cannot be used if the weather is poor or cloudy. A Massawe

6. Observing the universe • Many objects in space do not give out visible light but give out other types of energy-carrying waves like and • The Planck space telescope detects radio waves microwaves microwaves A Massawe

7. Observing the universe • detect radio waves coming from space, they are usually very large and expensive. • Advantage over optical telescopes – 1. 2. Radio telescopes can be used in bad weather because the radio waves are not blocked by clouds as they pass through the atmosphere. can also be used in the daytime as well as at night. A Massawe

8. Telescopes mirrors lenses • Telescopes use and to bend, magnify and focus the light. • Parallel light rays entering a convex lens come out and pass through at a point known as the • Converging lenses are used in a focal point refracting telescope A Massawe

9. Investigating converging lenses • A Converging lens can be used to produce a magnified image. The amount of magnification depends on: 1. 2. Two types of image can be seen. 1. A Is the image formed where the light rays are focused. 2. A is one from which the light rays appear to come, but don’t actually come from that image like in a plane (flat) mirror. How curved the surface of the lens is How far the object is from the lens real image virtual image A Massawe

10. Investigating converging lenses • Object more than two focal lengths from the lens image is inverted, smaller, appear between 1 and 2 focal lengths, real image A Massawe

11. Investigating converging lenses • Two focal lengths in front image is inverted, same size, appears at 2 focal lengths, real image A Massawe

12. Investigating converging lenses • Between one and two focal lengths image is inverted, made bigger, appear beyond 2 focal lengths, real image A Massawe

13. Investigating converging lenses • One focal length no image is formed A Massawe

14. Investigating converging lenses • Object is less than one focal length from the lens. image right way up, image made bigger, virtual image A Massawe

15. Refracting telescopes • A refracting telescope works by bending light through a lens so that it forms an image • Problems with refracting telescopes: 1.2. some of the light reflects off the lens so the image is very faint the size of the lens is limited A Massawe

16. Reflecting telescopes curved mirror • In a reflecting telescope the image is formed by reflection from a • It is then magnified by a Convex lens (the eyepiece) A Massawe

17. Compare and contrast lenses and mirrors 1. A convex lens acts a lot like a concave mirror. Both converge parallel rays to a focal point, and form images with similar characteristics. 2. A concave lens acts a lot like a convex mirror. Both diverge parallel rays away from a focal point, and form only virtual, smaller images. Similarities A Massawe

18. Compare and contrast lenses and mirrors 1. Light reflects from a mirror. Light goes through, and is refracted by, a lens (with some light being reflected off the lens).2. Lenses have two focal points, one on either side of the lens. 3. A concave mirror converges parallel light rays to a focal point. For lenses, parallel rays converge to a point for a convex lens. A convex mirror diverges light, as does a concave lens. Differences A Massawe

19. Refraction in different materials Remember the word: TAGAGA Towards (normal) Air Glass Away (from normal) Glass Air A Massawe

20. Effects of refraction A Massawe

21. Effects of refraction A Massawe

22. What are waves? vibrations that transfer energy • Waves are from place to place without matter (solid, liquid or gas) being transferred, e.g. Mexican wave in a football crowd visible light infrared rays microwaves other types of electromagnetic radiation sound waves seismic waves A Massawe

23. Transverse or longitudinal waves? Longitudinal waves the vibrations are along the parallel to the direction of travel e.g. - sound, - P waves (a type of seismic wave) the vibrations are at right angles to the direction of travel e.g.- light, - electromagnetic radiation, - water waves, - S waves (a type of seismic wave) A Massawe

24. What are waves? wavelength amplitude • The is the distance between a point on one wave and the same point on the next wave • The is the maximum distance of the particles in a wave from their normal positions • The of a wave is the number of waves produced by a source each second. frequency A Massawe

25. How fast do waves travel? • wave speed (m/s) = frequency (Hz) × wavelength (m) wave speed frequency wavelength A Massawe

26. Reflection reflect angle of reflection • Sound waves and light waves from surfaces. The angle of incidence equals the • Smooth surfaces produce strong when sound waves hit them • Rough surfaces sound and light in all directions echoes scatter A Massawe

27. Refraction change speed • Sound waves and light waves when they pass across the boundary between two substances with different densities, e.g. air and glass. • This causes them to change direction and this effect is called • There is no change in direction if the waves cross the boundary at an angle of - in that case they carry straight on (although there is still a change in speed). refraction 90° A Massawe

28. Electromagnetic spectrum Wavelength () increases Frequency (f) increases Gate XUsually Lets In Most Radiation Can you think of a phrase that would help you remember this order? Low frequency Long wavelength Low energy Least penetrating High frequency Short wavelength High energy Most penetrating High frequency Short wavelength High energy Most penetrating Low frequency Long wavelength Low energy Least penetrating A Massawe

29. Hazards of electromagnetic radiation cause internal heating of body tissues Microwaves Infrared radiation is felt as heat and causes skin burns damage cells, causing mutations (which may lead to cancer) and cell death X rays Gamma rays also damage cells, causing mutations (which may lead to cancer) and cell death. A Massawe

30. The three main types of ultraviolet radiation, and some of their effects A Massawe

31. Uses of electromagnetic radiation Radiowaves • – broadcasting, communications & satellite transmissions • – cooking, communications & satellite transmissions • - cooking, thermal imaging, short range communications, optical fibres, TV remote controls & security systems • – vision, photography & illumination Microwaves Infrared Visible light A Massawe

32. Uses of electromagnetic radiation Ultraviolet • – security marking, fluorescent lamps, detecting forged bank notes & disinfecting water • - observing the internal structure of objects, airport security scanners & medical X-rays • - sterilising food and medical equipments, detection of cancer and its treatment X-rays Gamma A Massawe

33. Exam tip • To make your answer as full as possible you should include: 1. the advantages and disadvantages of each type of radiation 2. clearly indicate the precise use and why 3. include information about frequency and wavelength A Massawe

34. Ionising radiation • Alpha, beta and gammaare ionising radiation: they can knock electrons out of atoms and form charged particles • Radiation can be harmful, but it can also be useful - the uses of radiation include to: 1. detect smoke 2. gauge the thickness of paper 3. treat cancer 4. sterilise medical equipment. A Massawe

35. Types of radiation radioactive • Nuclear radiation comes from the nucleus of an atom of substances which are • All radiation transfers energy. There are three types of nuclear radiation: alpha, beta and gamma alpha beta gamma A Massawe

36. The solar system • The solar system consists of: 1. a star - the Sun 2. satellites - moons - in orbit around most of the planets 3. comets and asteroids in orbit around the Sun. 4. eight planets, including the Earth, and smaller dwarf planets, such as Pluto, Ceres and Eris. A Massawe

37. Space exploration radio telescopes • The Search for Extra-Terrestrial Intelligence (SETI) is a programme that uses to look for non-natural signals coming from space • photograph planets looking for evidence of life • touch down on planets and take a soil sample, which is analysed for evidence of life. Space probes Space landers A Massawe

38. What is a spectrometer? • Spectrometer is an instrument that can split up light to show the colours of the spectrum A Massawe

39. The origins of the Universe • Scientists believe that the universe began in a hot 'big bang' about 13 billion years ago • Two evidences of the Big Bang Theory are; 1. the existence of a microwave background radiation, 2. red-shift. A Massawe

40. Other theories for the origin of the universe Oscillating Theory • The suggests that this universe is one of many - some that have existed in the past, and others that will exist in the future • When the universe contracts in a Big Crunch, a new universe is created in a new Big Bang. • The suggests that as the universe expands new matter is created, so that the overall appearance of the universe never changes. Steady State Theory A Massawe

41. Life cycle of a star A Massawe

42. The future of other stars masses • The life of stars depend on their . A heavy-weight star will still become a red giant, but then: 1. it blows apart in a huge explosion called a supernova 2. the central part left behind forms a neutron star, or even a black hole, if it is heavy enough 3. black holes have a large mass, and a large gravity - even light cannot escape them because their gravitational field is so strong A supernova is an exploding star A Massawe

43. Evidence for the Big Bang Theory • Red-shift - red is a longer wavelength of light, this means that the galaxies must all be moving away from us • Cosmic Microwave Background radiation - electromagnetic radiation which was present shortly after the big bang is now observed as background microwave radiation. • A satellite called COBE mapped the background microwave radiation of the universe A Massawe

44. Evidence for the Big Bang Theory The other galaxies are moving away from us. This evidence can be used to explain both the Big Bang theory and Steady State universe. The most likely explanation is that the whole universe is expanding. This supports the theory that the start of the universe could have been from a single explosion. The relatively uniform background radiation is the remains of energy created just after the Big Bang. A Massawe

45. Doppler effect for a moving sound source Long wavelength Low frequency Short wavelength High frequency A Massawe

46. Ultrasound and infrasound longitudinal • Sound waves are waves that must pass through a medium • have a frequency above the normal range of human hearing - they can be used to 1. 2. • has a frequency below normal hearing - can be used to 1. 2. Ultrasound waves scan for birth defects in unborn babies scan for defects in manufactured equipment. Infrasound track animals monitor seismic activity A Massawe

47. Sound waves • When an object vibrates, it produces sound. The bigger the vibrations, the greater the amplitude and the louder the sound • 1 and 2 - two sounds with the same frequency but different amplitude. Sound 1 (smaller amplitude) is quieter than sound 2. • 2 and 3 - two sounds with the same amplitude but different frequencies. The faster the vibrations, the higher the frequency and the more highly pitched the sound. • So sounds 2 and 3 have the same volume (loudness), but 3 (higher frequency) is higher pitched. A Massawe

48. Ultrasound • When ultrasound waves reach a boundary between two substances with different densities, they are partly reflected back and detected • e.g. sound travels through water at about 1,400 m/s. If it takes 0.5 s for a sound to reach a boundary and reflect back to the detector, the total distance travelled is: distance = speed × time = 1,400 × 0.50 = 700m A Massawe

49. Sonar • Sonar is used on ships and submarines to detect fish or the sea bed. • A pulse of ultrasound is sent out from the ship. • It bounces off the seabed or shoal of fish and the echo is detected. • The time taken for the wave to travel indicates the depth of the seabed or shoal of fish A Massawe

50. Infrasound • Infrasound has frequency less than 20Hz, this is below the range that humans can hear (20-20,000Hz). • Infrasound is detected using a microphone. • Three uses of infrasound: 1. to detect volcanic eruptions - as a volcano erupts itproduces infrasound, which can be detected even if the volcano is in a remote location far away 2. to track the passage of meteors through the atmosphere 3. to track animals (elephats use infrasound to communicate) even if they are hidden in dense forests. This helps with the conservation and protection of these animals. A Massawe