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P1 topic 1
Visible light and the solar system
Question | Answer |
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What is a geocentric model and who originally suggested it? | A model that places the earth in the centre of the solar system, suggested by Ptolemy |
What is a heliocentric model and who originally suggested it? | A model that places the sun in the centre of the solar system, suggested by Copernicus |
How did Galileo's observations support Copernicus's heliocentric model? | Galileo discovered 4 of Jupiter's moons using a telescope, and by plotting their movements he showed that not everything orbited Earth. This and other observations led him to support Copernicus's idea. |
What is refraction? | The change of speed and direction of a wave at the interface of 2 materials |
What is a lens? | A transparent block that has been shaped so that its interface changes the directions of parallel light waves |
What is a converging lens? | A glass block that is curved on both sides to make it thicker in the middle |
How can the focal length of a converging lens be measured? | Using a convex lens, the image of a distant object can be focused onto a screen. The focal length of this lens can be found by measuring the distance between the screen and the lens. |
How does a refracting telescope work? | Light rays from a distant object are nearly parallel when they reach us. A convex lens (the objective lens)forms an image in the tube by focusing these rays and the eyepiece lens magnifies the image. |
Why are waves refracted at a boundary between 2 materials? | Refraction occurs as light travels at different speeds in different materials. Waves travel slower in denser materials, so when moving from a less dense to a more dense material, light rays slow down and bend towards the normal, changing direction. |
How does the eyepiece of a telescope magnify the image produced by an objective lens? | The eyepiece lens spreads the light rays out so they leave at a wider angle than they entered it. Therefore the light rays fill more of your retina, making the image look bigger (magnified). |
What is the difference between and real image and a virtual image? | A real image is an image in which the rays of light actually meet at the point where the image is seen. A virtual image is an image in which the rays are diverging, so the object looks further away than it actually is. |
What is reflection? | The 'bounce back' of light at the interface of 3 materials. |
What are some disadvantages of using refracting telescopes? | Light is reflected at both lens, making the image fainter. Refracting telescopes also need to be long to have large magnifications, and large lens improve the magnification but are heavy and difficult to make in a perfect shape. |
How does a reflecting telescope work? | The curved primary mirror focuses parallel light rays from a distant object. The secondary mirror, placed just before the focal point of the primary mirror, reflects these rays into an eyepiece lens which magnifies the image. |
What are transverse waves and what is an example? | Waves in which particles move at right angles to the direction that the wave is going in. Electromagnetic waves are transverse, so they don't need a medium through which to travel |
What are longitudinal waves and what is an example? | Waves in which particles move back and forth in line with the direction that the wave is going. Sound waves are longitudinal, so they cannot travel through a vacuum |
True or false: waves transfer energy and matter. | FALSE: Waves transfer energy and information without transferring matter |
What is the frequency of a wave? | The number of waves passing a point each second, measured in Hertz (Hz) |
What is the wavelength of a wave? | The distance from a point on one wave to the same point on the next wave, measured in metres (m) |
What is the amplitude of a wave? | The maximum distance of a point on the wave from its rest position, measured in metres (m) |
How can wave speed be measured? | Wave speed = distance / time Wave speed = frequency x wavelength |