Flashcards
Physics 7
Cards in this deck (80)
- 1What is a solar eclipse?The time is takes for the sun to appear to be back in the same position of the sky (24 hours)
- 2What is a sidereal day?-The time it takes for a start o appear to be back in the same position (23 hours 56 mins)
- 3What is the direction that objects appear to rise and set?-From east to West
- 4How are solar and sidereal days different?-Solar: caused by the Earth orbiting the sun
-Sideral: caused by Earth spinning on axis - 5Why is it that a solar day is longer than a sidereal day?-Earth needs to rotate a bit longer than 360 to get the sun in the same place as it orbits in the same direction as spinning
- 6Why are lunar days the longest? How long are lunar days?-The moon orbits the Earth in the same direction that it rotates
-25 hours - 7What is an eclipse?When a planet or a moon gets in the way of the sunlight reaching Earth
- 8What is a solar eclipse? -What is the shadow on Earth called?-When the moon blocks the Sun's light
-Umbra - 9What is it called when we are facing a completely dark moon and a completely bright moon?-New moon
-Full moon - 10What is a Lunar eclipse?-When the Earth blocks the sunlight for the moon
-Moon seems to disappear as no light can be reflected - 11What are two reasons why eclipses don't happen every month-Earth rotates on an angle
-Moon, Sun and Earth have to be in a straight line - 12What is refraction of light?When light rays travel slower in more dense mediums, causing them to bend towards the normal
- 13What is the focus of a converging lense?When all initial parallel lines meet
- 14What is the focal length?-Distance from the middle of the lens to the focus point
- 15What effect does the focal length have on lenses?-The more powerful the lens, the closer the focus point and the shorter the focal length
- 16What are some of the rules about drawing light rays through lenses?-If ray goes through centre it keeps travelling straight
-If travels on principal axis it travels straight
-When coming into contact with a surface, the ray bends towards the normal
-Distant objects have parallel light rays
-If coming from a focus point, will turn to parallel - 17How do you calculate the magnification of a lense?Focal length of objective/ focal length of eyepiece
- 18Which lens is used as an eyepiece on a telescope and what does it do?-Fatter lens
-Magnifies image - 19Which lens is used as an objective on a telescope and what does it do?-Thinner lens
-Collects light and makes image clearer - 20How are the two lenses in a telescope aligned?-The principal axis is placed, so the focal points are in the same position
- 21Why is the focal point also called the real image?-This is where all the points actually meet
- 22What is the use of an objective lens?-To magnify and make the image clearer, using light collected
- 23What is sometimes used, opposed to lenses, in astronomical telescopes? Why is this the case?-Large concave mirrors
-Lenses tend to sag and deform
-Mirrors can be smoother, providing undistorted images
-Some types of light can not travel through lenses - 24What is the use of parallax?To measure nearby stars
- 25What can you infer about the size of a parallax angle?-The smaller the angle, the further away the object is
- 26How do you find the distance of a star in parsecs?1/ angle in arsecs
- 27What observed brightness depend on?-How far a star is
-This is because, if two stars have the same intrinsic brightness, that which is further away, would seem dimmer as the intensity of light rays decease with distance - 28What is a cephid variable?A star that pulses and changes its brightness over several days
- 29What can you tell about a cephid star?If two cephid variables have the same apparent brightness, but one has a longer pulse rate, you know that the one with the longer pulse rate is further away. This is because the pulse rate is linked to the intrinsic brightness, the brighter the star, the longer the puls
- 30What is a nebula?-Cloud of gas
- 31What is the Curtis-Shapley debate?-A debate on the size and structure of the universe
-They argued about what nebulae were and where they were situated - 32What was Shapley's argument?-Universe was just one galaxy
-We wrre far from the centre
-Nebulae were clouds of gas and dust and part of the Milky Way - 33What was Curtis' argument?-The Universe was made up of lots of different galaxies
-The Sun was very near the centre of ours, the Milky Way
-That Nebulae were distant separate galaxies - 34Who was right about what on the Curtis-Shapely argument?Curtis : -Universe made up of different galaxies and nebulae being far away
Shapley:- We are not near the centre of the Milky Way - 35What is Hubble's Law?Speed of recession = Hubble's constant x distance
- 36How did Hubble help solve the Curtis-Shapley debate-Used the largest telescope at the time to observe spirals
-Noticed that they contain stars, cephid variables
-Calculated the distance and realised that they were 2.5 million light years away, which is too far to be in our galaxy
-Decided that they were galaxies themselves - 37Why does redshifting occur?If an object is moving further away from us the wavelengths elongate, making the object posses wavelengths similar to the colour red, meaning that the object would appear red.
-The faster it travels, the more red it looks - 38What pattern did Hubble also come up with?-The further away the galaxy the faster it moves
- 39What is absolute zero?-The coldest that things can be as atoms have as little kinetic energy as possible
-273 degrees/ 0 kelvin - 40What happens to atoms when more temperature is added?-They are supplied with more kinetic energy, and move round more
- 41How do you convert from Celsius to kelvin?-Add 273
- 42What is the relationship between Pressure Temperature Volume?-Temperature is directly proportional to the other two
-Pressure and volume are indirectly proportional - 43What is pressure caused by?-Particles colliding with the walls
- 44Explain why an increase in temperature leads to an increase of pressure.Pressure is caused by when the particles collide with walls of container. So when temperature is increased there is more knietic energy given to the particles, so they move more, thus colliding more with the walls or container and harder creating more pressure
- 45What is the structure of a star?-Core
-Radiative zone
-Convective zone
Photosphere - 46What are the stages of fusion that occurs on the Sun?1. Hydrogen + Hydrogen-- Deuterium + positron
2. Deuterium + Hydrogen ---- Helium + energy
3. Helium + Helium ----Helium + Hhydrogen - 47What is nuclear fusion?-When two nuclei fuse together to form a bigger and heavier nucleus
- 48What happens in the core of the Sun?Fusion takes place here
-Hot and dense due to Sun's pressure, so nuclei are close enough to fuse - 49What happens in the convection zone?Transfers energy released from core, using convectional currents
- 50What happens in the photosphere?-Energy is radiated to space
-The part that we see
-Coolest part
-Rising and lowering from convection currents - 51What is the life cycle of a star?1.Main sequence star
2. If small (I.S) Red Giant, If big (I.B) Red Supergiant
3. I.S, white dwarf then cold black dwarf
4. I.B Supernova, then either neutron star or black hole - 52What does aperture mean?-Diameter of objective lens
- 53Why do we need a big aperture when studying faint sources?-The wider the aperture, the more information can be collected. This means that the data would be clearer and a better image
- 54What is one characteristic about the aperture of an objective lens?-It must be bigger than the wavelength. This is so that no diffraction occurs, as well as the distortion of the image
- 55What are some advantages of using telescopes that can be controlled by a computer-Can be controlled from office
-Programmed to be positioned
-Radio astronomy: lots of different telescopes needed to face the same direction
-Space telescopes are possible
- - 56How is the atmosphere a disadvantage for telescopes?-It only lets some wavelengths through and blocks the others.
-e.g. Radio waves are easily transmitted, by visible light is often effected - 57Why is visible light sometimes blurred when looking through a telescope on Earth?-The visible light is sometimes refracted by the water in the atmosphere.
-It is also sometimes absorbed by dust particles in the air - 58What is the solution to the atmosphere's effects on telescopes?-Put a telescope in space
- 59Name one difference between a space telescope and those on Earth.-Earth's tend to use lenses whereas space telescopes use mirrors
- 60Name 3 characteristics that need to be met when finding a place to set up an observatory-Lots of visible light, remote locations to avoid man made pollution
-As little atmosphere as possible, high altitudes
-Dry and low humidity - 61What practical factors need to be taken into account when setting up an observatory?-Cost of building, running and closing
-Access, as well as electricity and other facilities
-Environment and the effect observatories have on it
-Social benefits, like jobs - 62What do colours tell us about the temperature of stars?-The higher the frequency, the hotter the star
-Red: fairly cool
-Blue: very hot - 63What does intrinsic brightness mean? -What is the opposite?-The real and actual brightness of an object/star
-Apparent brightness - 64What does the peak frequency show?-The higher the peak frequency, the hotter the star
- 65How can you tell which star is hottest, just by looking on a graph?-The one with the highest peak fequency and largest area under the curve
- 66How can you judge or predict what colour a star would look, just by using a graph?-Assign the peak frequency to a specific colour on the line spectrum, if it falls between the frequencies, and that is the colour it will be
- 67What is black body radiation?-Radiation that is being emitted but not seen
-All radiation except for visible light - 68What does a decrease in volume give?An increase in pressure
- 69What is the difference between an absorption spectrum and an emission spectrum?-Absorption spectrum shows the energy that the electrons take/use/ steal, when heated, in order for them to jump between levels.
-Emission spectrum shows the energy the electrons give back when they have cooled down and thought about what they did.
-Absorbtion is black lines, emissions is coloured lines - 70What is the use of line spectra?-To identify what stars are made of
- 71What is the first stage of the fusion that occurs in main sequence stars?-Hydrogen + Hydrogen ---Deuterium + positron
- 72How do you notate a positron? Where do positrons come from?Same as an electron/ beta particle but with at positive 1
-When a proton loses its positivity to become a neutron, during the first stage of hydrogen fusion. - 73How is it possible that nuclei of the same charge are able to fuse?-High temperatures
-High pressures - 74What type of energy is released during hydrogen fusion?-Gamma rays
- 75How are the positions of stars measured?-Using the angles we see from Earth
- 76What is the pole star?A star that is directly above the axis of the Earth, so it doesn't appear to move
- 77What is the Celestial Equator?-An imaginary line that runs through space, originating and in line with the Earth's equator
- 78What are the two measurements to find a star's position?-Declination- How far up from celestial equator
-Right ascension- How far from 0 hours across - 79The closer the orbit to the Sun.............the quicker the planet
- 80If the right ascension of a planet increases, what can you say about the planet?-It is moving east
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- Flashcards on Physics 7, created by Sparkle Shine on 22/06/2016.
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