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Description
Flashcards by hannahegrice, updated more than 1 year ago
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Created by hannahegrice
about 10 years ago
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| Question | Answer |
| What did ancient Greeks thought was at the centre of the universe? | Earth, and that everything orbited the Earth in perfect circles this is know as the geocentric model |
| In the 1600's what model began to replace the geocentric model | The Heliocentric model this states that the earth and planets orbit the sun in the centre of the universe. the idea first came about in 1543 but they where not excepted at the time. |
| What was one of the most convincing pieces of evidence for the heliocentric model? | Galileo's observations of Jupiter's moons |
| What where Galileo's observations of Jupiter? | In 1610, he was observing Jupiter using a telescope when he saw three stars in a line near the planet. when he looked again the next night the stars had moved in the wrong direction, after a week a forth star appeared. the stars never moved away from Jupiter and seemed to be carried along with the planet. he then realised that they where not stars but moons and that they orbited Jupiter. |
| What did Galileo's observation of the moons show? | That not everything orbited earth which proved the geocentric model wrong |
| What does the current model of the solar system say? | The sun is the centre of the solar system and that the planets orbit the sun but the orbits are elliptical not circular |
| How has technology improved our ideas about about the solar system. | Technology like telescopes enables us to be able to see things you can't with the naked eye and it leads to the discovery of planets like uranus |
| How has scientists found out most of the things it knows about the universe? | From detecting waves from objects in space. some objects like stars are huge, very hot and very far away from us , they give out lots of visible lights which is why you can see them. you can see planets as they reflect the sunlight |
| How did early astronomers observe the universe? | They used the naked eye to discover stars, comets, and planets. they where very small to the naked eye so only used for mapping their positions |
| What do telescopes do? | Magnify images, so distant objects can be seen in more detail. you can also see things that are a greater distance away |
| What do photographs of the universe taken by telescopes do? | they enable you to zoom in and look at objects in more detail. it makes it easier to to monitor an object by taking pictures at different times to compare them. you can also see faint objects by allowing long exposure time so you collect more light |
| What is wavelength | the distance from one peak to the next |
| What is frequency on a wave? | How many complete waves there are per second (passing a certain point) |
| What is frequency measured in? | Hertz (Hz) 1Hz=1wave per second kHz=1000Hz MHz=1000000Hz |
| What is amplitude? | the hight of the wave from the mid-line to the peak |
| What is speed? | How fast it goes |
| What do waves transfer and what do they not? | Waves transfer energy and information they don't transfer matter |
| What is the formula that links speed, frequency and wavelenght | Speed = Frequency X Wavelenght |
| What unit is speed measured in? | m/s |
| What is wavelength measured in? | m |
| What formula links wave speed, distance and time? | Wave speed = distance ------- time |
| What are the properties of a Transverse wave? | The vibrations travel at 90 degrees to the direction of the wave. (up and down) S-wave Light and all other EMwaves |
| What are the features of a Longitudinal wave? | The vibrations move in the same direction as the wave is travelling (side to side) P-wave Sound and ulrasound |
| What is reflection? | When a wave hits a boundary between one medium and another, some of it's energy is reflected. The angle of of reflection, r, is the same as the angle of incidence, i. Light is reflected because of a change in density. |
| What is refraction? | waves travel at different speeds depending on density. when a wave is in a dense material it will travel slower than in a less dense material. Refraction happens when a wave crosses a boundary the wave will change speed. if a wave goes from less dense to more dense it will slow down and if its at an angle the waves will change direction towards the normal line. if it goes from more dense to less dense it will move away from the normal line. |
| What is a real image? | Its when the light from an object comes together to form an image on a 'screen'. the light will go through a converging or convex lens and the image will be upside down |
| What is a virtual image | It is when the rays are diverging, so the light appears to be coming from a completely different place. you see a virtual image when the image is the same side of the lens as the object. it is the right way up and larger |
| What are converging or convex lenses use for? | used to focus light by causing parallel rays of light to move together to a focus. |
| What is the focal point? | It is where rays hitting the object parallel to the axis all meet. |
| What is the axis of a lens? | The line passing through the middle of the lens. |
| Where are the focal points of a lens? | Each lens has a focal point in front of the lens and one behind the lens |
| How do you draw a ray diagram for an image through a converging lens? | 1) pick a point at the top of your object 2) draw a ray going from the top of the object to the lens parallel to the axis. 3) draw another ray going from the top of the object through the centre of the lens. 4) the incident ray (1st one) is refracted through the focal point on the axis 5) mark where the two rays cross. this is the top of your image, draw your image |
| What is focal length? | The distance from the lens to its focal point |
| How can you work out focal length? | 1) clamp a lens at one end of a track, then clamp white card further down the track. 2) set up the equipment near a window with the lens directed at a distant object. you should be able to see the object on the card. turn off any lights in the room to make the object more visible 3) move the card along the track until the image is focused 4) when in focus measure the distance between the centre of the lens and the card. this is your focal length |
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