P7 - Keywords Flashcards
Solar day
A full 24 hours
Retrograde motion
The apparent backwards motion of planets from west to east due to the combined motion of earth and the planet
Eclipse
The “hiding” of one heavenly body behind another
Ecliptic
The apparent path the sun traces across the sky
Sidereal day
The time it takes the earth to rotate 360 degrees; 23 hours 56 minutes
Refraction
The change in direction and speed of a wave as it passes from one medium to another.
Diffraction
The spreading out of a wave as it passes an obstacle and expands into the region beyond the obstacle
Frequency
The number of times that a wave oscillates in a second measured in Hertz
Wavelength
The distance between corresponding points on two adjacent waves
Focal point
The point at which all light rays parallel to the axis of the lens converge
Focal length
The distance between the focal point and the lens
Real image
An image produced by rays of light meeting at a point
Angular magnification
A means of measuring the magnification based on the angle of rays of light from an object compared to the angle the image appears to make
Dispersion
When light going through a lens is split
Chromatic aberration
When different colour of light are spread around the focus and produce a blurred image
Aperture
The opening of a telescope through which light enters
Parallax
The apparent movement of an object ; the movement is actually caused by motion of the observer
Light year
The distance light travels in a year
Luminosity
The brightness of a star, dependent on its size and temperature
Observed (or relative) intensity/ luminosity/ brightness
The brightness of a star from earth
Cepheid variable
A star that has a changing luminosity
Universe
A collection of galaxies
Galaxy
A collection of stars and planets
Nebula
An interstellar cloud of dust, hydrogen gas and plasma; another galaxy in the making
