Coursework Booklet 2

Transcription

1 Level 3 Applied Science UNIT 16: Astronomy and Space Science PHYSICS SECTION Coursework Booklet 2 1 P a g e

2 Astronomy and space science Learning aim B Undertake measurement and observation of astronomical objects Pass criteria 1. Poster listing types of telescopes, each with a diagram, and what part of the EM spectrum is being used. Refractor. Newtonian, Cassegrain and Coude reflectors. Details of the Mauna Kea observatory as being an Earth based telescope. Details of the Hubble Space telescope as being a space based telescope. Details of telescopes which detect the different parts of the EM spectrum presented as a POSTER. 2. General mode of operation of a telescope. Ray diagrams for reflecting and refracting telescopes. Practical determination of focal lengths for converging lenses. Practical determination of prime focus for convex mirrors. Log book of observational records of the Moon phases set against constellation position. Log book of observational records of Sun Spots. Practical determination of focal lengths of converging and diverging lenses. Practical determination of the focal length and prime focus of converging and diverging mirrors. Assess the effectiveness and the need for parabolic mirrors. Merit criteria 3. Working with independence to: Assess results from observations rotation of the Moon and Sun spots. Draw suitable conclusions. Show accuracy and precision and correct positioning of night sky objects against background of stars identified by right ascension and declination. Distinction criteria 4. Evaluation of practical observations. Identify errors in observations with relevant comments made about visual aspects, inaccuracies of measurements and suitability of equipment. Collect data and present it against an accurately illustrated star map. Suggestion of improvements. 2 P a g e

3 1. Types of telescopes Distant stars and galaxies are impossible for us to study with the naked eye, and too far for us to go and see them the nearest star is just over 4 light years away which means it would take light 4 years to get there, but it would take us over 81,000 years assuming we were travelling at 56,000 km/h. Because of this, we must analyse the radiation given off by these stars and galaxies using telescopes on Earth. There are 2 main types of telescopes reflectors and refractors. Reflecting telescopes use mirrors and refracting telescopes use lenses. These can either be Earth-based or space-based. 1.1 Refracting telescopes Refracting telescopes are optical instruments which use lenses to form an image. The work by converging light through the objective lens before diverging the light through the eyepiece lens. These telescopes are used to observe the visible-light region of the EM spectrum. The problems with refractors are: Figure 1: refracting telescope ray diagram. Not all the light is refracted, some is reflected which means the image is very faint. Large lenses are needed to improve magnification which can be difficult to do perfectly. 1.2 Reflecting telescopes In a reflecting telescope, the image is formed by a reflection from a curved mirror which is then magnified by a secondary mirror. Figure 2: reflecting telescope ray diagram. 3 P a g e

4 There are 3 main types of reflecting telescopes: Newtonian, Cassegrain, and Coude Newtonian Cassegrain Coupe 4 P a g e

5 1.3 Earth-based telescopes Advantages Easy to fix and maintain. Cheaper 10 to 20 times cheaper than space telescope. Disadvantages Can only be used at night. Cannot be used in cloudy weather. They are limited by atmospheric conditions Earth s atmosphere absorbs much of the infrared and UV that passes through it. Table 1: comparing the advantages and disadvantages of Earth-based telescopes. Figure 3: Mauna Kea observatory in Hawaii. Task: read these articles and summarise the different types of telescopes in terms of the radiation they detect in the table below. Telescopes How many are there? Type of radiation detected Keck telescopes Very large baseline array James Clerk Maxwell telescope 5 P a g e

6 1.4 Space-based telescopes Advantages No atmospheric gases in space so the image is not distorted. Can observe near-infrared and UV that normally would be blocked by the atmosphere. Disadvantages Cost to operate. Cost to fix and upgrade. Cultural conflict. Can detect all parts of the EM spectrum. Table 2: comparing the advantages and disadvantages of space-based telescopes. Figure 4: The Hubble space telescope. The Hubble space telescope was the first major optical telescope to be placed in space. Scientists have used Hubble to observe the most distant stars and galaxies as well as the planets in our solar system. The telescope does not travel to stars, planets or galaxies, it takes pictures of them as it orbits the Earth at about 17,000 mph. It is 13.3 metres long (the size of a large school bus) and its primary mirror is 2.4 metres across. It detects radiation from UV to visible, to near-infrared wavelengths. 6 P a g e

7 Figure 5: illustration of the parts of the EM spectrum that get blocked by Earth s atmosphere. Earth based telescopes are suitable to detect visible and radio waves from distant source, whereas space-based telescopes are more suited to detecting the remaining EM radiation. 1.5 Telescopes observing other parts of the EM spectrum Telescope Wilkinson Microwave Anisotropy Probe James Webb Space Telescope Hubble Space Telescope Chandra X-ray Observatory Fermi Gamma-ray Space Telescope Section of EM spectrum detected Microwaves Infrared Visible and ultraviolet X-rays Gamma rays Website NOTE: These telescopes are ALL space based. YOU NEED AN IMAGE OF EACH AND TO WRITE A BRIEF DESCRIPTION ABOUT THE MISSION OF EACH TELESCOPE THIS NEEDS TO BE PRESENTED AS A POSTER!! 7 P a g e

8 2. General mode of operation You need a hand-drawn ray diagram of each type of telescope in your coursework. 8 P a g e

9 2.1 Determining focal lengths of refracting telescopes Aim To determine the focal length of a converging lens. Equipment 1 light source, 1 converging lens, a ruler, 1 calculator and a piece of paper. Method Figure 6: set up of equipment needed to find the focal length of a converging lens. 1) Set up the equipment as shown in figure 6 (you will need a hand drawn copy of this diagram). 2) Place the light source where it says object, the lens a suitable distance away and measure this gives the value of u, and record in the table below. 3) Then move the paper away from the lens until an image is formed. At this point, measure the distance from the lens to the image this gives a value of v, and record in the table. 4) Calculate 1/u and 1/v, and then use the equation 1 = to find 1/f. f u v 5) Then find the reciprocal of 1/f to find f. 6) Repeat two more times to check accuracy of result. Results 1 Trial u 1/u v 1/v 1/f f 2 3 Improvements Health and Safety 9 P a g e

10 Aim To determine the focal length of a diverging lens. Equipment 1 light source, 1 converging lens, 1 diverging lens, a ruler, 1 calculator and a piece of paper. Method Figure 7: set up of equipment needed to find the focal length of a diverging lens. 1) Set up the equipment as shown in figure 7 (you will need a hand drawn copy of this diagram). 2) Place the light source before the convex lens the same distance as before. The focal length will be the same as the previous practical, f 1. 3) Place the concave lens on the right hand side of the convex lens. 4) Then move the paper away from the concave lens until an image is formed. At this point, measure the distance from the lens to the image this gives focal length 2, f 2. 5) Calculate 1/f 1 and 1/f 2, and then use the equation 1 F = 1 f f 2 to find 1/F. 6) Then find the reciprocal of 1/F to find F. 7) Repeat two more times to check accuracy of result. Results 1 Trial f 1 1/f 1 f 2 1/f 2 1/F F 2 3 Improvements Health and Safety 10 P a g e

11 2.2 Determining the prime focus of a concave mirror. Aim To determine the focal length of a concave mirror. Equipment Twin-hole ray box, concave mirror, 1 ruler, a calculator, and a piece of paper. Method Figure 8: set up of equipment needed to find the prime focus of a concave mirror. 1) Set up the equipment as shown in figure 8. 2) Place the light source before the concave mirror, and measure the distance between them. Record this in the table under letter o. This value will be taken as negative as it is behind the image. 3) Move the paper back and forth until you get a clear image and measure that distance, i. 4) Calculate 1/o and 1/i, and then use the equation 1 = to find 1/f. i o f 5) Then find the reciprocal of 1/f to find f. 6) Repeat two more times to check accuracy of result. Results 1 Trial o 1/o i 1/i 1/f f 2 3 Improvements Health and Safety 11 P a g e

12 2.2 Determining the prime focus of a convex mirror. Aim To determine the focal length of a convex mirror. Equipment 2 convex mirrors, a ruler, and a calculator. Method 1) Measure the radius of curvature and record in the table below. 2) Divide that value by 2. 3) Repeat twice more. 4) Repeat with another convex mirror. Figure 9: illustration to determine the focal point of a convex lens. 1 Lens Trial 1 Trial 2 Trial 3 Average focal length Radius of curvature Focal length Radius of curvature Focal length Radius of curvature Focal length 2 Improvements Health and safety 12 P a g e

13 2.3 Effectiveness of mirrors over lenses Mirrors have many advantages over lenses for large telescopes: Glass absorbs infrared light so lenses would not be a suitable option to take infrared pictures. So, to understand temperatures of stars or space objects, we would use mirrors. Lenses exhibit optical problems such as spherical and chromatic aberration which prevents them from focusing light to a single point and thus producing an unclear image. (This is discussed in more detail below). It is easier to make a large mirror than a large lens. A mirror only requires fabrication on one side, whereas a lens requires both. Highly purified lenses are required to obtain high quality images, which increases the cost Spherical aberration Figure 10: illustration of spherical aberration of a lens mirrors do not have this problem. The parallel light rays of incoming light do not converge at the same point after passing through the lens. The light rays at the top and bottom of the lens are refracted more than the ones in the middle so form a focus before the other light rays. We can reduce spherical aberration by using non-spherical lenses which curve outwards on one side. 13 P a g e

14 2.3.2 Chromatic aberration Chromatic aberration occurs due to dispersion of white light as it passes through glass. The red light is refracted the least and blue to most so we get a separation of colours which affects the final image. Figure 11: illustration of chromatic aberration or the dispersion of light. YOU MAY HAVE SEEN THIS DURING YOUR EXPERIMENT again, mirrors are not affected by this. 3. Observing moon phases against the constellations Task: you need to observe the phase of the Moon every night for 2 weeks, and draw the details of the moon you see each night below. YOU MUST INCLUDE THE CONSTELLATIONS AROUND THE MOON AND ANY PROMINENT STARS AND PLANETS. You may want to use these websites to help you this website gives you the right ascension and declination of the Moon each night. Their observations will be set onto an independently constructed map of a suitable portion of the night sky, with paths of objects shown against labelled constellations, and stars and distances accurately measured This is taken directly from the mark scheme. Binoculars will be useful for this task to ensure you include all the main surface details of the Moon. 14 P a g e

15 3.1 Moon phase observations Monday 30 th October Phase: Tuesday 31 st October Phase: 15 P a g e

16 Wednesday 1 st November Phase: Thursday 2 nd November Phase: 16 P a g e

17 Friday 3 rd November Phase: Saturday 4 th November Phase: 17 P a g e

18 Sunday 5 th November Phase: Monday 6 th November Phase: 18 P a g e

19 Tuesday 7 th November Phase: Wednesday 8 th November Phase: 19 P a g e

20 Thursday 9 th November Phase: Friday 10 th November Phase: 20 P a g e

21 Saturday 11 th November Phase: Sunday 12 th November Phase: 21 P a g e

22 3.2 Moon phases discussion, conclusion, and improvements For this section, you need to assess and evaluate your results. You need to answer the following questions. What do your results conclude about the Moon s rotation? Are your results accurate and how do you know this? (Compare with others and astronomical data) Are your results reliable and how do you know this? 22 P a g e

23 What were the main sources of error? (Hint: visual aspects, inaccuracies of measurements, suitability of equipment for purpose). What could you do to improve the accuracy and reliability of your observations? 23 P a g e

24 4. Observing Sun spots Sun spots are cooler regions of the Sun (about 2000 K cooler than the surface) and form continuously as the Sun s magnetic field actively moves through the Sun. Sun spots follow an 11 year cycle but each individual spot has a life time between hours and months. Your task: over a period of 5 days you need to observe sunspot activity. This will be done using a telescope and projecting the Sunspots onto a screen for you to draw. You will need to mark the angles at which the telescope is pointed to ensure you observe the same area each time. Record your observations below: From these observations of Sun spot activity, you should be able to calculate the rotational period of the Sun. Note the dimensions of the Sun spot s position below: Use this website to help you find the initial location of the sun spots: 24&h=00&m=00#ra dec fov 51 Figure 12: right ascension and declination of the Earth. This is comparable to the Sun. YOU NEED TO LABEL THE UMRA AND PENUMBRA OF THE SUNSPOTS. Figure 13: diagram showing the umbra and penumbra of a Sun spot. The Sun s surface surrounding the spot is grainy. 24 P a g e

25 4.1 Sun spot observations Observations of Sun spots - day 1 Date: 25 P a g e

26 Observations of Sun spots - day 2 Date: 26 P a g e

27 Observations of Sun spots - day 3 Date: 27 P a g e

28 Observations of Sun spots - day 4 Date: 28 P a g e

29 Observations of Sun spots - day 5 Date: 29 P a g e

30 4.2 Sun spots discussion, conclusion, and improvements Did any spots appear to change size or shape? What did you notice about their positions over the days? (Did other groups sunspots move the same amount over these four days?) If the Sun spots rotate by degrees every day, how long does it take the Sun to complete a complete rotation? 30 P a g e

31 Are your results accurate and how do you know this? (Compare with others and astronomical data) Are your results reliable and how do you know this? What were your main sources of error? (Hint: visual aspects, inaccuracies of measurements and suitability of equipment for purpose). 31 P a g e

32 How could you improve your results? 32 P a g e