Q: What is meant by the retrograde motion of Mars, and how did Ptolemy try to explain it? Q: What is the geocentric model of the Solar System?

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1 Q: What is the geocentric model of the Solar System? Q: What is meant by the retrograde motion of Mars, and how did Ptolemy try to explain it? Q: Who proposed the heliocentric model of the Solar System? Q: What are the features of the heliocentric model of the Solar System? Q: What were the strengths of Copernicus heliocentric model? Q: What problems were associated with Copernicus heliocentric model? Q: How did Johann Kepler improve on Copernicus model? Q: What were Galileo s contributions to disproving the geocentric model of the Solar System?

2 A: Most of the time Mars moves in a certain direction but every so often it appears to stop and then changes direction. Ptolemy tried to explain this backwards motion by using a model to make the planet move in a circle (called an epicycle) on top of its circular orbit. The model started to look quite complex and still failed to predict the exact positions of the planets. A: Proposed by Ptolemy ( CE) nearly 2000 years ago. It constituted the Earth, five planets (Mercury, Venus, Mars, Jupiter, Saturn), the Moon, the Sun and the stars. All heavenly objects moved round the Earth, which was at the centre of the Solar System. The Earth is stationary. The Moon, Sun, planets and stars move round the Earth in circular orbits. A: The planets, including the Earth, went round the Sun in circular orbits. The planets furthest from the Sun moved more slowly. The Moon went around the Earth. The stars formed a dome beyond the planet Saturn. A: At this time the Roman Catholic Church believed the Earth s rightful place was at the centre of the Solar System. Copernicus was a devout Catholic and did not want to upset the Church. He only published his ideas close to his death. However, it was as bad as Ptolemy s model at predicting the position of the planets because it still used circular orbits. A: He discovered four moons orbiting Jupiter (proving that not all heavenly bodies orbited the Earth) and observed the phases of Venus, which can only be explained if the Earth and Venus orbited the Sun, and if the orbit of Venus was between the Earth and the Sun. A: Nikolaus Copernicus ( CE). A: It was successful at explaining the retrograde motion of Mars. Mars moves backwards against the stars when the fast-moving Earth overtakes it. It was much simpler than Ptolemy s model. A: He realised that the planets had elliptical (oval-shaped) orbits.

3 Q: How were a) Uranus, and b) Pluto discovered? Q: Describe the components of the Solar System. Q: How can astronomers use naked eye observation to investigate the Universe? What are its limitations? Q: How do astronomers use telescopes to investigate the Universe? What are their limitations? Q: How can astronomers use photography to investigate the Universe? Q: What parts of the electromagnetic spectrum can the Hubble space telescope take images in? Q: What has the Chandra space probe, launched in 1999, been used to investigate? Q: What has the Herschel space observatory, launched in 2009, been used to investigate?

4 A: The Sun, a star, surrounded by the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune; an asteroid belt, consisting of lumps of rock, lies between Mars and Jupiter (the largest asteroid, Ceres, is 974 km); Pluto, demoted to a dwarf planet in 2006 because of its small size; the Kuiper belt consisting of frozen objects (mainly methane, ammonia and water) that lie mostly beyond Neptune (thought to be the source of comets); the Oort cloud, lying at a distance of 1.5 ly from the Sun, consisting of billions of small lumps of rock and ice (too faint to be seen using visible light). A: a) William Herschel used a large telescope to discover Uranus in 1781; b) Pluto was discovered using photographic techniques in A: Telescopes magnify images, so distant objects can be seen in more detail. You can also see objects that are at larger distances. Many new objects have been discovered using telescopes and they have helped us learn more about what the Universe is made up of. Telescopes on Earth have problems though. Space telescopes overcome these issues, but they are expensive. A: Early astronomers made observations of the Universe just using the naked eye. Many very important discoveries of stars, comets and planets were made this way. Most astronomical objects are so far away and look so small that naked eye observations are only really useful for mapping their positions. A: Visible light, infrared, ultraviolet. A: Herschel uses infrared waves to take images. Cooler objects emit a greater amount of infrared waves than visible light. Among other things, infrared astronomy may help to gather information about the Kuiper belt. A: Photographs of the Universe can be taken using telescopes this allows you to zoom in and look at objects in more detail. It makes it easier to monitor an object by taking pictures at different times to compare them, and to share your observations with others. You can also see faint objects by allowing a long exposure time so you collect more light, which obviously can t be done with just the naked eye. A: Chandra takes images in X-rays. It has successfully taken images of distant galaxies and our own Milky Way. X-rays are emitted when electrons are slowed down or when electrons hit atoms at high speeds.

5 Q: How do you work out the focal length of a converging lens using a distant object? Q: What is a real image? Q: What is a virtual image? Q: What is the focal length of a lens? Q: What are the three rules for drawing a ray diagram for refraction at a converging lens? Q: Describe the image formed by a particular converging lens when the object is beyond 2F. Q: Describe the image formed by a particular converging lens when the object is at 2F. Q: Describe the image formed by a particular converging lens when the object is between 2F and F.

6 A: Image formed on the other side of a converging lens to the object a real image can be formed on a screen. A: The distance between the middle of a lens and its focal point. A: The image is real, inverted, diminished and found between F and 2F. A: Clamp the lens at one end of a track. The clamp a piece of white card further down the track. Set up this equipment near a window with the lens directed at a distant object, e.g. a nearby building you should be able to see an image of the object on the piece of card. Turn off any lights in the room to make the image more visible. Move the card along the track until the image is focused (this is where the picture looks sharpest). When you ve got the best image you can, clamp the piece of card in place so it does not move. Use a ruler to measure the distance between the centre of the lens and the card this is the focal length. A: Image formed on the same side of the lens as the object a virtual image can be seen looking through the lens, it cannot be projected onto a screen. A: 1. An incident ray parallel to the axis refracts through the lens and passes through the focal point on the other side. 2. An incident ray passing through the focal point before entering the lens will refract through the lens and travel parallel to the axis. 3. An incident ray passing through the centre of the lens carries on in the same direction. A: The image is real, inverted, magnified and found beyond 2F. A: The image is real, inverted, the same size as the object and found at 2F.

7 Q: Describe the image formed by a particular converging lens when the object is between F and the lens. Q: How do we calculate the magnification of an image? Q: What is the function of the objective lens of a simple telescope? Q: How does the eyepiece lens of a telescope work? Q: How does a reflecting telescope work? Q: What are the laws of reflection? Q: Why is light reflected at a boundary? Q: What is refraction?

8 A: Magnification = image height / object height A: The image is virtual, upright, magnified and found beyond F (on the same side of the lens as the object). A: Rays of light from the real image enter the eyepiece. The lens spreads them out so they leave at a wider angle than they entered it, and so the light rays fill more of your retina, making the image look magnified. A: 1. The angle of incidence i is equal to the angle of reflection r (angles measured relative to the normal). 2. The incident ray, reflected ray and normal lie in the same plane. A: The bending of a wave caused by the change in its speed when a light ray travelling through air enters a glass block it changes direction. A: It converges parallel rays of light from a distant object to form a real image at the focal point of the objective lens. A: A large concave mirror collects the parallel rays of light from an object in space. The larger mirror reflects this light into a smaller second mirror placed in front of the large mirror s focal point. The smaller mirror reflects the light through a converging eyepiece lens to magnify the image. A: Because of a change in density, e.g. water is denser than air. Whenever a wave reaches a medium with a different density, some of the wave is reflected at the boundary.

9 Q: Why are waves refracted at a boundary between two materials? Q: What happens when light travels from a less dense material to a more dense material? Q: What happens when light travels from a more dense material to a less dense material? Q: What is a wave? Q: What is meant by the frequency of a wave? Q: What is meant by the wavelength of a wave? Q: What is meant by the term speed? Q: What is what by the amplitude of a wave?

10 A: It slows down, and therefore bends towards the normal line. A: They transfer energy and information from one place to another; they create vibrations; they do not transfer matter in the direction they are travelling. A: Refraction is caused by the change in the speed of light at the boundary between two materials. The speed of light depends on the density of the material, e.g. it travels much more slowly in water than air. A: It speeds up, and therefore bends away from the normal line. A: Distance between neighbouring wave peaks (or troughs). A: The number of vibrations per second or number of complete waves passing a set point per second. A: Maximum displacement of a wave measured from the mean position. A: How fast an object travels, calculated using the equation: speed (metres per second) = distance / time.

11 Q: Describe the features of a transverse wave. Q: What are some examples of transverse waves? Q: Describe the features of a longitudinal wave. Q: What are some examples of longitudinal waves? Q: Mathematically, what is the relationship between wave speed, distance and time? Q: Mathematically, what is the relationship between wave speed, wavelength and frequency? Q: What is the unit of measurement of frequency? Q: If v = f x λ, what are the expressions for finding f and λ?

12 A: Light and all other EM waves, seismic S waves, waves on strings and springs, ripples on water. A: The vibrations are at 90 o to the direction of travel of the wave. A: Sound, ultrasound, infrasound, seismic P waves, a slinky spring when you push and pull the end. A: The vibrations are along the same direction as the wave is travelling. A: Wave speed (metre per second, m/s) = wavelength (metre, m) x frequency (hertz, Hz) (or v = f x λ). A: Wave speed (metre per second, m/s) = distance (metre, m) / time (second, s) (or v = x / t). A: f = v / λ and λ = v / f. A: Hertz, Hz.