P7 Keywords

Question 1

solar day

Answer 1

The average time it takes for the sun to cross the sky (24 hours on earth)

Question 2

celestial sphere

Answer 2

an imaginary sphere with the earth at its centre and the stars fixed to the surface of the sphere

Question 3

sidereal day

Answer 3

When a day is measured by the movement of the stars (earth day would be 23 hours 56 minutes)

Question 4

retrograde motion

Answer 4

when plants appear to slow down and go into reverse instead of moving from east to west (similar path to sun and moon) as usual.

Question 5

solar eclipse

Answer 5

when the moon is perfectly aligned to block the suns light from reaching Earth

Question 6

lunar eclipse

Answer 6

when the Earth moves into the moons shadow

Question 7

angular size

Answer 7

an angular measurement describing how large a sphere or circle appears from a given point of view. (the sun is 400x the diameter of the moon and is also 400x as far away meaning they coincidentally have the same angular size)

Question 8

optical telescopes

Answer 8

Were the first telescopes and use visible light

Question 9

aperture

Answer 9

a hole or an opening through which light travels, the size of the aperture is dependant on how clear far away images appear

Question 10

converging lenses

Answer 10

is curved on both sides. This means the light rays coming out of it come together at a point – they converge.

Question 11

principal axis

Answer 11

A horizontal line passing through he centre of the lens

Question 12

refraction

Answer 12

When Light changes direction when it passes at an angle from one material to another.
When light speeds up as it passes from one material to another, the angle of refraction is bigger than the angle of incidence.

Question 13

focal length

Answer 13

The distance from the centre of the lens to the focus

Question 14

dioptres

Answer 14

A mathematical unit used to measure the power of a lens

Question 15

eyepiece lens

Answer 15

The lens next to your eye, it is the smaller but stronger lens

Question 16

objective lens

Answer 16

The lens next to the object, it is the larger but weaker lens

Question 17

spectrometer

Answer 17

used to measure the amount of radiation received at different frequencies

Question 18

angular magnification

Answer 18

the ratio of the angle subtended at the eye by the image formed by an optical instrument to the angle subtended at the eye by the object being viewed.

Question 19

prism

Answer 19

a triangular block

Question 20

dispersion

Answer 20

the splitting of white light into colours

Question 21

grating

Answer 21

a set of narrow parallel lines on a shiny surface, when light shines on it, different colour emerge at different angles produce several spectra.

Question 22

Diffraction

Answer 22

When the aperture of a telescope causes blurring to the image by the waves spreading.
(It can be stopped by having an aperture much large than the wavelength)

Question 23

Parallax

Answer 23

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.

Question 24

Parallax angle

Answer 24

The parallax angle is the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star. Astronomers use this angle to find the distance from the Earth to that star.

Question 25

parsec

Answer 25

a unit of distance used when measuring parallax angles

Question 26

luminosity

Answer 26

A power output; it is the energy it gives out each second by radiating light and other types of electromagnetic radiation

Question 27

nebula

Answer 27

a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter.

Question 28

globular cluster

Answer 28

a spherical collection of stars that orbits a galactic core as a satellite

Question 29

comet

Answer 29

a celestial object consisting of a nucleus of ice and dust and, when near the sun, a ‘tail’ of gas and dust particles pointing away from the sun.

Question 30

asteroid

Answer 30

a small rocky body orbiting the sun. Large numbers of these, ranging in size, are usually found between the orbits of Mars and Jupiter

Question 31

planetary nebula

Answer 31

a ring-shaped nebula formed by an expanding shell of gas round an ageing star

Question 32

supernova

Answer 32

This is when fusion stops in a red super giant so the mass collapses and causes a huge explosion (supernova) that will either form a neutron star or black hole

Question 33

neutron star

Answer 33

made after a small supernova, it is a star consisting entirely of neutrons mad when the protons and electrons essentially fuse together during the explosion

Question 34

black hole

Answer 34

From the product of a large supernova it is a region of space having a gravitational field so intense that no matter or radiation can escape (vacuum)

Question 35

supernova remnant

Answer 35

This is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion