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21C Science


A Sidereal day is ...... The time taken for the earth to spin 360 degrees (or the time to see a star in the same position in the sky)
The length of a sidereal day is... 23 hours 56 minutes
A sidereal day occurs because.... The earth is moving around the sun so its position changes in relation to other stars.
A solar day is.... The time taken for the sun to appear in the same position in the sky
The length of a solar day is .... 24 Hours
The length of time for the moon to eturn to the same position in the sky.... 25 hours
The reason why the stars appear to move in the sky... Because the direction we face changes slighty each day.
The reason why the moon appears to shine ..... it reflects the suns light (only the side facing the sun is lit up the other side is in shadow)
When do we see a full moon ? When the whole of the lit up surface is facing us.
When do we see a new moon ? when the side in shadow is facing us
When do eclipses happen ? When light from the sun is blocked
The two main types of eclipses ? Lunar and Solar
A Lunar eclipse occurs when... the moon passes into the Earths shadow
A solar eclipse occurs when ... The moons shadow falls on the Earth
The reason why eclipses dont happen very often is because.... The moon orbits the earth at a slight angle.
The year of the next total solar ecclipse visiable from the uk 2090
The star that doesn't seem to move when viewed from the earth is... Pole star
The reason the pole star doesn't appear to move is... because it is directly above the north pole and therefore the spin axis of the earth
The imaginary plane running across the sky extending from the earths equator is... The celestial equator.
The distance a star moves upwards (celestial latitude) Declination
The distance a star moves across the sky (celestial longitude) is called.. Right Ascension
The imaginary line passing through the centre of a lens is called the.... principal axis
The number of focal points in each lens 2 (one in front and one behind the lens)
The distance between the middle of the lens and its focal point is called.... the focal length
Focal length is related to... Power
1. The more powerful the lens the.... more strongly it converges rays of light.
2. The more powerful the lens... the shorter the focal length.
Power = 1/focal length
3. The more powerful the lens... the more strongly curved the surfaces
An image formed where light rays appear to have come from is called a ... Virtual image
A simple refracting telescope uses... 2 converging lenses
Magification = focal length of objective lens / focal length of eye lens
Most astrnonical telescopse use .... a concave mirror
Concave mirrors are like a portion of a ... sphere (the centre of the sphere is the centre of curvature or C)
Halfway between the centre of curvature vertex is .... the focal length
calculating magnification with powers = power of eyepiece / power of objective lens
The distance to nearby stars can .... be measured by parallax
1 arcsec = 1/3600 degrees
1 parsec = 3 light years approximately
distace in parsecs= 1 / angle in arcsecs
Observed brightness depends on ... the intrinsic brightness of the star and its distance from the veiwer.
Speed of recession of distance galaxies (km/s)= Hubble constant x distance
The value of the hubble constant is roughly.... 2 x 10-18 (10 to the minus 18)
If you increase the temperature of something you... give the particles more kinetic energy.
the way to convert degrees celcius to kelvins is... add 273
A decrease in volume of a gas results in.. an increase in pressure (if temperature remains constant)
An increase in temperature of a gas results in.. an increase in pressure (if volume stays constant)
Created by: garethphillips3