08/06/2016 Unit 1 – Universal Physics N Smith St. Aidan’s (EdExcel)

Topic 1 – Visible Light and the Solar System 08/06/2016

Our understanding of the universe 08/06/2016 Ptolemy, AD Copernicus, Up until the 16 th Century people believed that the Earth was the centre of the universe – this is called the “Geocentric model” and I made a model of the universe based on it. I published my “On the revolutions of the celestial spheres” just before my death and showed that the Earth and other planets orbit around the sun – the “Heliocentric model”.

Evidence for the Heliocentric Model 08/06/2016 Galileo, Jupiter and its moons, as seen through a telescope The orbits of these moons I helped develop the modern telescope and made measurements with it that proved that the Copernican model of the solar system was correct.

08/06/2016 Observing the Universe What are the advantages and disadvantages of each of these methods? A complex digital camera will be in here

08/06/2016 An introduction to Waves A Wave is a “movement of energy” but NOT a transfer of matter

08/06/2016 Wave definitions… 1) Amplitude – this is “ how high ” the wave is: 2) Wavelength ( ) – this is the distance between two corresponding points on the wave and is measured in metres: 3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz) 4) Speed – this is how fast the wave travels and is measured in metres per second (m/s)

08/06/2016 Transverse vs. longitudinal waves Transverse waves are when the displacement is at right angles to the direction of the wave. Longitudinal waves are when the displacement is parallel to the direction of the wave… Displacement Direction Displacement Examples – light, other EM waves, some seismic waves Examples – sound, some seismic waves

08/06/2016 Refraction through a glass block: Wave slows down and bends towards the normal due to entering a more dense medium Wave speeds up and bends away from the normal due to entering a less dense medium Wave slows down but is not bent, due to entering along the normal

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Refraction Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this: In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______. Words – speed up, water, air, bent, medium

08/06/2016Lenses Lenses use the idea of refraction: When light enters a MORE DENSE medium it slows down… A prism uses this idea to split light. This happens because purple light is refracted more than red light

08/06/2016 Another example: The lens in the eye is used to focus what we see:

08/06/2016 Converging and diverging lenses CONVERGING (Convex) Thickest at the centre DIVERGING (Concave) Thinnest at the centre

08/06/2016 Ray diagrams for lenses 1 The rays of light are refracted INWARDS and meet at the focus, F. The image formed is REAL – in other words, it can be seen on a screen The rays of light are refracted OUTWARDS. A VIRTUAL image is formed – in other words, the image doesn ’ t actually exist F F A “distant object” Focal length

08/06/2016 Lenses in Telescopes Because stars are very far away, the rays of light from them enter a telescope effectively parallel: Eyepiece lens Focal point Objective lens (convex) The objective lens basically gathers as much light as possible from the distant star and focuses it inside the telescope. The eyepiece lens then magnifies this image into the eye.

08/06/2016 Mirrors in Telescopes Astronomical telescopes tend to use large concave mirrors as well as a convex lens. This allows them to collect more light: Objective lens (convex) Eyepiece lens Concave mirror Flat mirror

08/06/2016 The Wave Equation All E-M waves obey the Wave Equation: Wave speed (v) = frequency (f) x wavelength ( ) in m/s in Hz in m V f

08/06/2016 1)A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? 2)A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? 3)The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? 4)Purple light has a wavelength of around 6x10 -7 m and a frequency of 5x10 14 Hz. What is the speed of purple light? Some example wave equation questions 0.2m 0.5m 0.6m/s 3x10 8 m/s

08/06/2016 Distance, Speed and Time for waves Speed = distance (in metres) time (in seconds) D TS 1)A water wave travels 200 metres in 40 seconds. What is its speed? 2)Another wave covers 2km in 1,000 seconds. What is its speed? 3)Sound travels at around 330m/s. How long does it take to travel one mile (roughly 1,600m)? 4)Light travels at a speed of 300,000,000m/s. How long would it take to travel around the world if the diameter at the equator is around 40,000km?

Topic 2 – The Electromagnetic Specturm 08/06/2016

The Visible Spectrum 08/06/2016 Isaac Newton, In the 17 th Century I did lots of work on light and wrote about how visible light was made of the colours of the spectrum. William Herschel, I accidentally discovered that, if you put a thermometer here, it gets hot. I discovered Infra Red radiation!! Wilhelm Ritter, I then discovered ultra violet by observing how salts made from silver were lightened by something just beyond violet light.

08/06/2016 Electromagnetic Radiation E-M radiation is basically a movement of energy in the form of a wave. Some examples:

08/06/2016 The Electromagnetic Spectrum Gamma rays X-raysUltra violetVisible light Infra redMicrowavesRadio/TV Each type of radiation shown in the electromagnetic spectrum has a different wavelength and a different frequency: Each of these waves travels at the same speed through a _______ (300,000,000m/s), and different wavelengths are absorbed by different surfaces (e.g. infra red is absorbed very well by ___________ surfaces). They all travel as _____ waves. The more dangerous waves are at the high ________ end of the spectrum. Words – black, transverse, long, short, vacuum, frequency High frequency, _____ wavelength Low frequency, _____ (high) wavelength γ

08/06/2016 The Electromagnetic Spectrum Type of radiationUsesDangers Gamma rays X rays Ultra violet Visible light Infra red Microwaves TV/radio Treating cancer, sterilisation Medical, airport scanners Sun beds, security Seeing things, photos Remote controls, heat transfer, optical fibres Satellites, phones Communications Cell mutation Skin cancer None (unless you look at the sun) Skin burns Heating of cells Very few

08/06/2016 Introduction to Radioactivity Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation: Radiation The nucleus is more stable after emitting some radiation – this is called “radioactive decay”. Radiation like this can be either alpha, beta or gamma radiation.

08/06/2016Ionisation Radiation is dangerous because it “ ionises ” atoms – in other words, it turns them into ions by “ knocking off ” electrons: Ionising radiation is emitted by radioactive sources all the time. Ionisation transfers energy to cells in living tissue, causing them to mutate, usually causing cancer.

Topic 3 – Waves and the Universe 08/06/2016

Space: An introduction OUR SUN is one of millions of stars that orbit the centre of… THE MILKY WAY, which is one of a billion galaxies that orbit AND move away from the centre of… THE UNIVERSE, made up of everything!!

How our Earth and the Sun compare to others… 08/06/2016

Distances in space 08/06/2016 The Sun, our closest star, is 1.6x10 -5 light years away from us. The Andromeda Galaxy (our closest galaxy) – approximately 2.5 million light years away The next closest star, Proxima Centauri (4.2 light years away) The centre of our galaxy, the Milky Way, is around 26,000 light years away.

08/06/2016 Observing the Universe Consider different types of telescope: Radio telescopes Space-based telescopes The original telescopes were used purely for visible light. These days, telescopes pick up a wide range of waves. Some examples...

08/06/2016 Hubble Space Telescope (HST) Launched in 1990, due to finish operating in 2010 Takes images in the visible light, ultra-violet and near infra red regions Orbits the Earth every 97 minutes

08/06/2016 Infra Red Astronomical Satellite (IRAS) Surveys infra red patterns in space Launched in 1983 and operated for 11 months The number of known astronomical bodies was increased by 70% due to infra red observations

08/06/2016 Cosmic Background Explorer (COBE) Operated from 1989 to 1993 Detected small ripples in the Cosmic Microwave Background Radiation (CMBR) reaching the Earth

08/06/2016 Life on Other Planets Research task Is it likely that other planets in our solar system could have life? Explain your answer. Extend your inquiry to other solar systems – what criteria must be met in order for a planet to potentially have life on it?

08/06/2016 Searching for Aliens Humans have been searching for me for over 50 years. Here are some of the methods they use: SETI – The Search for Extra Terrestrial Intelligence Since 1960 a group of astronomers have collectively been sending out EM signals hoping that someone will send one back! Space probes The Voyager 1 probe, still in operation after over 33 years and still sending signals back to Earth. Soil samples Soil samples from the moon and, in recent years, from Mars have been sampled. What are the advantages and disadvantages of each of these methods?

How modern telescopes have helped 08/06/2016 Due to technological advances in telescopes our knowledge of the universe has been expanded. Some examples: Galileo 1) In 1610 I used a telescope to determine the existence of a galaxy around us – the Milky Way – due to better magnifications in my telescope. 2) Some stars don’t emit visible light, so they are “seen” by taking infra red photos and then applying “false colour”: 3) The Hubble Space Telescope has been able to take measurements to more accurately determine the age of the universe – around 14 billion years.

Making a simple spectrometer 08/06/2016 Slit

08/06/2016 Observing the Universe Consider different types of telescope: Ground-based telescopes Space-based telescopes What are the advantages and disadvantages of each?

08/06/2016 Benefits of observing above the atmosphere The amount of light absorbed by the atmosphere Bad weather Light is refracted, diffracted and scattered by the atmosphere (causing stars to “ twinkle ” ) Ground-based telescopes Clearly, ground-based telescopes are a problem because of a number of things:

08/06/2016 The Life Cycle of a Star

08/06/2016 Stage 1: Nebulae A nebulae is a collection of dust, gas and rock. Some examples of nebulae…

08/06/2016 Dark nebula

08/06/2016 Emission nebula