Biology revision - Yola

Biology revision - Yola

P1 - Universal physics Friday, February 14, 2020 A Massawe 1 How science works Independent variable this is the quantity that you change Dependent variable - this is what you measure Control variable this is what must be kept the same to ensure a fair test Hypothesis an idea based on observations without experimental evidence Secondary evidence - data collected by someone else, you may find it in a book or on the internet

Friday, February 14, 2020 A Massawe 2 How do scientist validate results? 1. they repeat experiment results 2. they publish their findings in scientific journals 3. conference presentation 4. peer review/other scientists investigate the same findings. Friday, February 14, 2020 A Massawe

3 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 Friday, February 14, 2020 A Massawe 4

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. they can only be used at night 2. they cannot be used if the weather is poor or cloudy. Friday, February 14, 2020 A Massawe 5

Observing the universe Many objects in space do not give out visible light but give out other types of energy-carrying waves like radio waves and microwaves The Planck space telescope detects microwaves Friday, February 14, 2020 A Massawe 6 Observing the universe Radio telescopes detect radio waves coming from

space, they are usually very large and expensive. Advantage over optical telescopes 1.can be used in bad weather because the radio waves are not blocked by clouds as they pass through the atmosphere. 2. can also be used in the daytime as well as at night. Friday, February 14, 2020 A Massawe 7 Telescopes

Telescopes use mirrors and lenses 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 focal point Converging lenses are used in a refracting telescope Friday, February 14, 2020 A Massawe 8 Investigating converging lenses A Converging lens can be used to produce a magnified image. The amount of magnification depends on: 1. How curved the surface of the lens is

2. How far the object is from the lens Two types of image can be seen. 1. A real image Is the image formed where the light rays are focused. 2. A virtual image is one from which the light rays appear to come, but dont actually come from that image like in a plane (flat) mirror. Friday, February 14, 2020 A Massawe 9 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 Friday, February 14, 2020 A Massawe 10 Investigating converging lenses Two focal lengths in front image is inverted, same size, appears at 2 focal lengths, real image Friday, February 14, 2020 A Massawe 11

Investigating converging lenses Between one and two focal lengths image is inverted, made bigger, appear beyond 2 focal lengths, real image Friday, February 14, 2020 A Massawe 12 Investigating converging lenses One focal length no image is formed

Friday, February 14, 2020 A Massawe 13 Investigating converging lenses Object is less than one focal length from the lens. image right way up, image made bigger, virtual image Friday, February 14, 2020 A Massawe 14

Refracting telescopes A refracting telescope works by bending light through a lens so that it forms an image Problems with refracting telescopes: 1. some of the light reflects off the lens so the image is very faint 2. the size of the lens is limited Friday, February 14, 2020 A Massawe 15 Reflecting telescopes In a reflecting telescope the image is formed by

reflection from a curved mirror It is then magnified by a Convex lens (the eyepiece) Friday, February 14, 2020 A Massawe 16 Compare and contrast lenses and mirrors Similarities 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. Friday, February 14, 2020 A Massawe 17 Compare and contrast lenses and mirrors Differences 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. Friday, February 14, 2020 A Massawe 18 Refraction in different materials Remember the word: TAGAGA Towards (normal) Air Glass Away (from normal)

Glass Air Friday, February 14, 2020 A Massawe 19 Effects of refraction Friday, February 14, 2020 A Massawe 20 Effects of refraction

Friday, February 14, 2020 A Massawe 21 What are waves? Waves are vibrations that transfer energy from place to place without matter (solid, liquid or gas) being transferred, e.g. Mexican wave in a football crowd Waves travel through medium No medium required sound waves seismic waves

visible light infrared rays microwaves other types of electromagnetic radiation Friday, February 14, 2020 A Massawe 22 Transverse or longitudinal waves? Transverse waves

Longitudinal waves the vibrations are at right the vibrations are along the parallel to the direction of angles to the direction of travel e.g. travel e.g. - sound, - light, - electromagnetic radiation, - P waves (a type of seismic wave) - water waves, - S waves (a type of seismic wave) Friday, February 14, 2020 A Massawe

23 What are waves? The wavelength is the distance between a point on one wave and the same point on the next wave The amplitude is the maximum distance of the particles in a wave from their normal positions frequency The of a wave is the number of waves produced by a source each second. Friday, February 14, 2020 A Massawe

24 How fast do waves travel? wave speed (m/s) = frequency (Hz) wavelength (m) wave speed frequency wavelength Friday, February 14, 2020 A Massawe 25 Reflection

Sound waves and light waves reflect from surfaces. The angle of incidence equals the angle of reflection Smooth surfaces produce strong echoes when sound waves hit them Rough surfaces scatter sound and light in all directions Friday, February 14, 2020 A Massawe 26 Refraction Sound waves and light waves change speed 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 refraction

is called There is no change in direction if the waves cross the boundary at an angle of90 - in that case they carry straight on (although there is still a change in speed). Friday, February 14, 2020 A Massawe 27 Electromagnetic spectrum Wavelength () increases Frequency (f) increases Gamma

X-ray Ultraviolet Light Infra-red Microwaves Radio Gate X of a phrase Usually Letshelp you Inremember Most

Radiation Can you think that would Low frequency this order? High frequency Highfrequency frequency Low Long wavelength Short wavelength High energy Short wavelength wavelength

Long Low energy Most penetrating Highenergy energy Low Least penetrating Most penetrating Least penetrating Friday, February 14, 2020 A Massawe

28 Hazards of electromagnetic radiation Microwaves cause internal heating of body tissues 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 Friday, February 14, 2020 also damage cells, causing mutations (which may lead to cancer) and cell death. A Massawe 29 The three main types of ultraviolet radiation, and some of their effects Type UV B

frequency hazard causes severe damage to cells, high skin cancer causes severe sunburn and medium damage to cells UV A low

UV C Friday, February 14, 2020 weaker effects than UV B A Massawe 30 Uses of electromagnetic radiation Radiowaves broadcasting, communications & satellite transmissions Microwaves cooking, communications & satellite transmissions Infrared - cooking, thermal imaging, short range communications, optical fibres, TV

remote controls & security systems Visible light vision, photography & illumination Friday, February 14, 2020 A Massawe 31 Uses of electromagnetic radiation Ultraviolet security marking, fluorescent lamps, detecting forged bank notes & disinfecting water X-rays - observing the internal structure of objects, airport security scanners & medical X-rays Gamma - sterilising food and medical equipments, detection of cancer and its

treatment Friday, February 14, 2020 A Massawe 32 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 Friday, February 14, 2020

A Massawe 33 Ionising radiation Alpha, beta and gamma are 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. Friday, February 14, 2020 A Massawe

34 Types of radiation Nuclear radiation comes from the nucleus of an atom of substances which are radioactive All radiation transfers energy. There are three types of nuclear radiation: alpha, beta and gamma alpha beta gamma Friday, February 14, 2020 A Massawe 35 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. Friday, February 14, 2020 A Massawe 36 Space exploration The Search for Extra-Terrestrial Intelligence (SETI) is a programme that uses radio telescopes to look for non-natural signals coming from space Space probes photograph

planets looking for evidence of life Space landers touch down on planets and take a soil sample, which is analysed for evidence of life. Friday, February 14, 2020 A Massawe 37 What is a spectrometer? Spectrometer is an instrument that can split up light to show the colours of the spectrum Friday, February 14, 2020

A Massawe 38 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. Friday, February 14, 2020 A Massawe 39

Other theories for the origin of the universe The Oscillating Theory 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 Steady State Theory suggests that as the universe expands new matter is created, so that the overall appearance of the universe never changes. Friday, February 14, 2020 A Massawe 40 Life cycle of a star Friday, February 14, 2020

A Massawe 41 The future of other stars The life of stars depend on their masses . A heavyweight 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 Friday, February 14, 2020 A Massawe

A supernova is an exploding star 42 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 Friday, February 14, 2020

A Massawe 43 Evidence for the Big Bang Theory Evidence Interpretation The other galaxies are moving away The light from other from us. This evidence can be used to galaxies is redexplain both the Big Bang theory and shifted. Steady State universe. The most likely explanation is that the The further away whole universe is expanding. This

the galaxy, the more supports the theory that the start of its light is redthe universe could have been from a shifted. single explosion. The relatively uniform background Cosmic Microwave radiation is the remains of energy Background (CMB) created just after the Big Bang. Friday, February 14, 2020 A Massawe

44 Doppler effect for a moving sound source Long wavelength Low frequency Friday, February 14, 2020 Short wavelength High frequency A Massawe 45 Ultrasound and infrasound Sound waves are longitudinal waves that must pass

through a medium Ultrasound waves have a frequency above the normal range of human hearing - they can be used to 1. scan for birth defects in unborn babies 2. scan for defects in manufactured equipment. Infrasound has a frequency below normal hearing can be used to 1. track animals 2. monitor seismic activity Friday, February 14, 2020 A Massawe 46 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. Friday, February 14, 2020 A Massawe 47 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 Friday, February 14, 2020 A Massawe 48 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 Friday, February 14, 2020 A Massawe 49 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 it produces 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. Friday, February 14, 2020 A Massawe 50 Seismic waves The crust and upper mantle are broken into large pieces called tectonic plates.

These plates move slowly, but can cause earthquakes and volcanes where they meet. The seismic waves produced by an earthquake are monitored and tracked. - liquid nickel and iron - Solid nickel and iron Friday, February 14, 2020 A Massawe 51 Seismic waves Earthquakes happen when large parts of the Earth's crust and upper mantle move suddenly Earthquakes produce shockwaves called seismic waves.

These waves can be detected using seismographs. type of wave relative speed can travel through Friday, February 14, 2020 P waves longitudinal faster solids and liquids A Massawe S waves

transverse slower solids only 52 Difference between S and P waves S-waves - transverse - slow moving - travel through solids only P-waves - longitudinal - fast moving - travel through liquids and solids only Friday, February 14, 2020

A Massawe 53 Producing electricity An electric current can be produced by moving a magnet inside a coil of wire attached to a sensitive ammeter, the needle is seen to move. This means the magnet causes the free electrons to move around the circuit as a current Friday, February 14, 2020 A Massawe 54 Producing electricity

Here the magnet is being pushed into the coil. The ammeter shows current induced in a positive direction. Now the magnet is stationary inside the coil. There is no current being produced in the coil, shown by the zero reading on the ammeter The magnet is being pulled out. The ammeter shows current being induced in the opposite direction to before. Friday, February 14, 2020 A Massawe 55

Producing electricity The size of this induced current can be increased by 1. move the magnet faster 2. use a stronger magnet 3. increase the number of turns on the coil 4. increase the area of the coil. Friday, February 14, 2020 A Massawe 56 Direct and alternative current Direct current DC, current flows in only one direction . Batteries and solar cells supply DC electricity. The diagram shows an oscilloscope screen

displaying the signal from a DC supply. Alternating current AC, current constantly changes direction. Mains electricity is an AC supply. The UK mains supply is about 230V. It has a frequency of 50Hz, which means that it changes direction and back again 50 times a second. Friday, February 14, 2020 A Massawe 57 Producing electricity Generators (bicycle dynamo) induce a current by spinning a magnet inside a coil of wire

When this happens, a potential difference - voltage - is produced between the ends of the coil, which causes a current to flow. As the bicycle moves, the wheel turns a magnet inside a coil This induces enough electricity to run the bicycle's lights The faster the bicycle moves, the greater the induced current and the brighter the lights. Friday, February 14, 2020 A Massawe 58 Large-scale electricity production Turning generators indirectly - generators can be turned indirectly

using fossil or nuclear fuels 1. Heat is released from fuel and boils the water to make steam. 2. The steam turns the turbine. 3. The turbine turns a generator and electricity is produced. 4. The electricity goes to the transformers to produce the correct Friday, February 14, 2020 A Massawe voltage 59 Different sources of energy Renewable energy resources include: wind energy tidal waves hydroelectric power geothermal energy

solar energy biomass energy, for example energy released from wood Friday, February 14, 2020 A Massawe 60 Solar cells or Solar energy Solar cells (or photocells) turn light energy from the Sun directly into direct current electricity. Advantages Disadvantages

Its renewable No maintenance No power lines required No fuel Long lifetime No green house gases Expensive to build Low efficiency requires large area Manufacture causes pollution Low power output Friday, February 14, 2020 A Massawe

61 Hydroelectricity A dam is built to trap water, usually in a valley where there is an existing lake. Water is allowed to flow through tunnels in the dam, to turn turbines and thus drive generators. Advantages Disadvantages No waste or pollution Very reliable Low running cost Quick start-up time Electricity can be generated constantly Friday, February 14, 2020

Requires hilly areas Destroys habitats Expensive to build A Massawe 62 Wind turbines Wind turbines (or aero-generators) use large blades to capture the kinetic energy of the wind. This kinetic energy is used to directly turn a turbine and produce electricity. Advantages Disadvantages No waste or greenhouse gases

No fuel is needed Can be tourist attractions Friday, February 14, 2020 Noisy May spoil views Kill birds The amount of electricity generated depends on the strength of the wind. A Massawe 63 Geothermal energy

Hot rocks underground heat water to produce steam. Holes are drilled down to the hot region, steam comes up to drive turbines, which drive electric generators Advantages Disadvantages No pollution No fuel is needed Easy and cheap to run Hot rocks are not available everywhere Geothermal site can run out of steam Hazardous gases or minerals may come up

Friday, February 14, 2020 A Massawe 64 Tidal power These work rather like a hydro-electric scheme, except that the dam is much bigger. Advantages Disadvantages Tidal range varies High power output Destroys habitats Reliable power source

Expensive to build Long lifetime Low running costs No fuel needed Tides are predictable Not expensive to maintain Friday, February 14, 2020 A Massawe 65 Biomass Wood is burnt to heat our homes and cook our food. Sugar cane can be fermented to make alcohol, which can be burned to generate power. Advantages

Disadvantages Difficult to collect or The fuel is cheap Less demand on the fossil grow large quantities It produce greenhouse fuel gases Friday, February 14, 2020 A Massawe 66 Transformers Transformers are used in the National Grid to

reduce energy losses from the wires during transmission. A transformer that increases the voltage is called a step-up transformer A transformer that decreases the voltage is called a step-down transformer e.g. adapters and rechargers for mobile phones and CD players. Friday, February 14, 2020 A Massawe 67 Transformers The ratio between the voltages in the coils is the same as the ratio of the number of turns in the coils primary voltage

= turns on primary secondary voltage turns on secondary This can also be written as: Vp/ = Np/ Vs Ns Step-up transformers have more turns on the secondary coil than primary coil. Step-down transformers have fewer turns on the secondary coil than the primary coil. Friday, February 14, 2020 A Massawe 68 Transformers

A transformer has 20 turns on the primary and 400 on the secondary. What is the output voltage if the input voltage is 500V? /Vs = Np/Ns Therefore Vs/Vp = Ns/Np Vs/ 400/ 500 = 20 Vs = 500 x (400/20) Vs= 10,000 Volts Vp Friday, February 14, 2020 A Massawe 69

Current A current flows when an electric charge moves around a circuit measured as the rate of flow of charge The current flowing through a component in a circuit is measured using an ammeter The units for current is amperes or A Friday, February 14, 2020 A Massawe 70 Potential difference (voltage) A potential difference, also called voltage, across an electrical component is needed to make a current flow through it. Potential difference across a component in a circuit is

measured using a voltmeter The voltmeter must be connected in parallel with the component. Friday, February 14, 2020 A Massawe 71 Power, current and potential difference Power is a measure of how quickly energy is transferred. You can work out power using this equation: power (W) = voltage (V) current (A) power

voltage Friday, February 14, 2020 current A Massawe 72 Power and energy Power is a measure of how quickly energy is transferred. You can work out power using this equation: energy transformed power

time A Massawe Friday, February 14, 2020 73 Paying for electricity The amount of electrical energy transferred to an appliance depends on its power, and on the length of time it is switched on for The amount of mains electrical energy transferred is measured in kilowatt-hours (kWh). One unit is 1kWh energy transferred (kWh) = power (kW) time (h) The cost of the electricity used is calculated using this equation: cost = power (kW) time (hour) cost of 1 kWh (pence)

Friday, February 14, 2020 A Massawe 74 Saving energy (cost efficiency) payback time = cost of energy-saving measure money saved each year e.g. Double-glazing might cost 2,500 and save 100 a year. What is the payback time? = 2,500 100 = 25 years Friday, February 14, 2020 A Massawe

75 Saving energy (cost efficiency) When buying an energy-saving device, it is important to consider the advantages and disadvantages. Some disadvantages would be: 1. initial cost 2. use of extra resources to manufacture new device 3. cost of disposal of old device. Some of the advantages would be: 1. cost efficiency 2. saving energy and resources. Friday, February 14, 2020 A Massawe 76

Energy transfer and efficiency Forms of energy - Most Kids Hate Learning GCSE Energy Names Magnetic - energy in magnets and electromagnets Kinetic - the energy in moving objects. Also called movement energy Heat also called thermal Friday, February 14, 2020 A Massawe 77 Energy transfer and efficiency Light also called radiant energy

Gravitational potential stored energy in raised objects Chemical stored energy in fuel, foods and batteries Sound energy released by vabrating objects Friday, February 14, 2020 A Massawe 78 Energy transfer and efficiency Electrical energy in moving or static electric charges Elastic potential stored energy in stretched or squashed objects

Nuclear stored in the nuclei of atoms Friday, February 14, 2020 A Massawe 79 Energy transfers Different types of energy can be transferred from one type to another, e.g. of useful energy transfer Friday, February 14, 2020 A Massawe 80

Sankey diagrams Sankey diagrams summarise all the energy transfers taking place in a process. The thicker the line or arrow, the greater the amount of energy involved. Friday, February 14, 2020 A Massawe 81 Calculating efficiency The efficiency of a device such as a lamp can be calculated using this equation: efficiency = useful energy transferred x 100 energy supplied

The efficiency of the filament lamp is (10 100) 100 = 10% - this means that 10% of the electrical energy supplied is transferred as light energy (90% is transferred as heat energy). The efficiency of the energy-saving lamp is (75 100) 100 = 75% - this means that 75% of the electrical energy supplied is transferred as light energy (25% is transferred as heat energy). Friday, February 14, 2020 A Massawe 82

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