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| Question | Answer |
| Describe | Use a sentence to link together ideas |
| Geocentric | A theory where everything orbits the earth (contradicted by Galileo’s observations) |
| Heliocentric | A theory where everything orbits the sun (confirmed by Galileo’s observations) |
| New planets | Planets recently discovered orbiting distant stars due to the ‘wobble’ of the star’s orbit |
| Milky way | The galaxy (collection of billions of stars) which contains our sun and the solar system |
| Solar system | The sun and 8 planets (Pluto is no longer considered a planet) |
| Galileo’s observations | He saw objects that were orbiting Jupiter – sometimes he could see 4 and other times he could only see 2 or 3 – they were the moons of Jupiter. |
| Galileo’s conclusions | If something orbited Jupiter that meant that not everything orbited the Earth – hence the geocentric theory was incorrect |
| Visible light | Electromagnetic radiation that can be detected by the human eye. Can be split up into the colours of the rainbow using a prism. |
| Naked-eye | Observations of space made without a telescope, very little detail can be seen and the only way to record them is by drawing a picture |
| Reflecting telescope | A telescope that uses a mirror to collect the light. It can collect more light than a refracting telescope because a mirror can be made larger than a lens and capture more light |
| Refracting telescope | A telescope that uses an objective lens (convex) to collect light. A disadvantage is that the colours of the light can be affected by the lens which is known as chromatic aberration. |
| Photography | A camera can be attached to a telescope – this allows a permanent record to be made of observations allowing the astronomer to take more time looking at the object and writing conclusions. |
| Focal length | The distance from a convex lens to where the light rays are focused on a single point. It can be measured by using a screen to project an image of a distant object and moving the screen until the image becomes clear. |
| Converging lens | A lens that refracts light onto a single point. The distance to the point is known as the focal length. |
| Eyepiece | A convex lens found in both reflecting and refracting telescopes which has the job of magnifying the image. |
| Magnify | To make bigger |
| Image | Can be ‘real’ (upside down) or ‘virtual’ (right way up – ‘erect’) |
| Objective lens | The lens at the front of the telescope which has the job of collecting the light. |
| Primary mirror | The concave mirror at the back of the reflecting telescope which collects the light and focuses it to a point. |
| Secondary mirror | This reflects the light onto the eyepiece lens. |
| Refraction | When a wave changes direction because it has changed speed as it crosses the boundary between two materials. |
| Boundary | The point where two materials meet e.g. glass and air. |
| Real image | An ‘inverted’ image (upside down) formed by a convex lens – it forms on the opposite side of the lens to the object being observed. |
| Virtual image | An ‘erect’ image (right way up) formed by a convex lens which forms on the same side of the lens as the object being observed. |
| Reflection | When a wave reflects (bounces off) the boundary between two materials (the angle of reflection and incidence are always the same) |
| How reflecting telescope works | Light is gathered by the primary mirror and reflected on the secondary mirror which reflects the light onto the eyepiece lens which magnifies the image. |
| How refracting telescope works | Light is gathered by the objective lens and refracted, the image is magnified by the eyepiece lens. |
| Wave | able to transfer energy and information but NOT matter, can be transverse or longitudinal. |
| Frequency | How many waves per second – measured in Hertz (Hz) |
| Wavelength | How long the wave is from the top of one wave (crest) to the top of the next wave (measured in metres (m)). |
| Amplitude | How ‘tall’ the wave is from the centre line (equilibrium line) to the top of the crest. |
| Wave speed | How fast the wave moves, calculated from frequency x wavelength. |
| Longitudinal | A wave where the oscillations (vibrations) are PARALLEL to the direction of wave travel |
| Transverse | A wave where the oscillations (vibrations) are AT RIGHT ANGLES to the direction of wave travel |
| Herschel’s experiment | When he split white light with a prism he observed that red light had a greater heating effect than violet, so he put a thermometer into the space where he could see no light next to the red light and found that there was even greater heating – he concluded there must be an invisible light there (‘infrared’ light) |
| Ritter’s experiment | When he split white light with a prism he observed that violet made photographic paper turn black faster than red light, so he put some photographic paper into the space where he could see no light next to the violet light and found that there was an even faster colour change – he concluded there must be an invisible light there (‘ultraviolet’ light) |
| Electromagnetic waves | Made up of oscillating magnetic and electric fields, they are TRANSVERSE and all travel at the same speed IN A VACUUM (speed of light) |
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