Q: What is the geocentric
model of the Solar
System?
Q: What is meant by the
retrograde motion of Mars,
and how did Ptolemy try to
explain it?
Q: Who proposed the
heliocentric model of the
Solar System?
Q: What are the features of
the heliocentric model of
the Solar System?
Q: What were the
strengths of Copernicus’
heliocentric model?
Q: What problems were
associated with
Copernicus’ heliocentric
model?
Q: What were Galileo’s
Q: How did Johann Kepler
contributions to disproving
improve on Copernicus’
the geocentric model of
model?
the Solar System?
A: Most of the time Mars moves in a certain
direction but every so often it appears to
stop and then changes direction. Ptolemy
tried to explain this backwards motion by
using a model to make the planet move in a
circle (called an epicycle) on top of its
circular orbit. The model started to look
quite complex and still failed to predict the
exact positions of the planets.
A: Proposed by Ptolemy (90-170 CE) nearly
2000 years ago. It constituted the Earth, five
planets (Mercury, Venus, Mars, Jupiter,
Saturn), the Moon, the Sun and the stars. All
heavenly objects moved round the Earth,
which was at the centre of the Solar System.
The Earth is stationary. The Moon, Sun,
planets and stars move round the Earth in
circular orbits.
A: The planets, including the
Earth, went round the Sun in
circular orbits. The planets
furthest from the Sun moved more
slowly. The Moon went around the
Earth. The stars formed a dome
beyond the planet Saturn.
A: Nikolaus Copernicus
(1473-1543 CE).
A: At this time the Roman Catholic Church
believed the Earth’s rightful place was at
the centre of the Solar System.
Copernicus was a devout Catholic and did
not want to upset the Church. He only
published his ideas close to his death.
However, it was as bad as Ptolemy’s
model at predicting the position of the
planets because it still used circular
orbits.
A: It was successful at
explaining the retrograde
motion of Mars. Mars moves
backwards against the stars
when the fast-moving Earth
overtakes it. It was much
simpler than Ptolemy’s model.
A: He discovered four moons
orbiting Jupiter (proving that not all
heavenly bodies orbited the Earth)
and observed the phases of Venus,
which can only be explained if the
Earth and Venus orbited the Sun,
and if the orbit of Venus was
between the Earth and the Sun.
A: He realised that the planets
had elliptical (oval-shaped)
orbits.
Q: How were a) Uranus,
and b) Pluto discovered?
Q: Describe the
components of the Solar
System.
Q: How can astronomers
use naked eye observation
to investigate the
Universe? What are its
limitations?
Q: How do astronomers
use telescopes to
investigate the Universe?
What are their limitations?
Q: How can astronomers
use photography to
investigate the Universe?
Q: What parts of the
electromagnetic spectrum
can the Hubble space
telescope take images in?
Q: What has the Chandra
space probe, launched in
1999, been used to
investigate?
Q: What has the Herschel
space observatory,
launched in 2009, been
used to investigate?
A: The Sun, a star, surrounded by the planets Mercury,
Venus, Earth, Mars, Jupiter, Saturn, Uranus and
Neptune; an asteroid belt, consisting of lumps of rock,
lies between Mars and Jupiter (the largest asteroid,
Ceres, is 974 km); Pluto, demoted to a dwarf planet in
2006 because of its small size; the Kuiper belt consisting
of frozen objects (mainly methane, ammonia and water)
that lie mostly beyond Neptune (thought to be the
source of comets); the Oort cloud, lying at a distance of
1.5 ly from the Sun, consisting of billions of small lumps
of rock and ice (too faint to be seen using visible light).
A: a) William Herschel used
a large telescope to discover
Uranus in 1781; b) Pluto was
discovered using
photographic techniques in
1930.
A: Telescopes magnify images, so distant
objects can be seen in more detail. You can
also see objects that are at larger distances.
Many new objects have been discovered
using telescopes and they have helped us
learn more about what the Universe is made
up of. Telescopes on Earth have problems
though. Space telescopes overcome these
issues, but they are expensive.
A: Early astronomers made observations
of the Universe just using the naked eye.
Many very important discoveries of stars,
comets and planets were made this way.
Most astronomical objects are so far
away and look so small that naked eye
observations are only really useful for
mapping their positions.
A: Visible light, infrared,
ultraviolet.
A: Photographs of the Universe can be taken
using telescopes – this allows you to zoom in
and look at objects in more detail. It makes
it easier to monitor an object by taking
pictures at different times to compare them,
and to share your observations with others.
You can also see faint objects by allowing a
long exposure time so you collect more light,
which obviously can’t be done with just the
naked eye.
A: Herschel uses infrared waves to
take images. Cooler objects emit a
greater amount of infrared waves
than visible light. Among other
things, infrared astronomy may help
to gather information about the
Kuiper belt.
A: Chandra takes images in X-rays.
It has successfully taken images of
distant galaxies and our own Milky
Way. X-rays are emitted when
electrons are slowed down or
when electrons hit atoms at high
speeds.
Q: How do you work out
the focal length of a
converging lens using a
distant object?
Q: What is a real image?
Q: What is a virtual image?
Q: What is the focal length
of a lens?
Q: What are the three rules
for drawing a ray diagram
for refraction at a
converging lens?
Q: Describe the image
formed by a particular
converging lens when the
object is beyond 2F.
Q: Describe the image
formed by a particular
converging lens when the
object is at 2F.
Q: Describe the image
formed by a particular
converging lens when the
object is between 2F and F.
A: Image formed on the
other side of a converging
lens to the object – a real
image can be formed on a
screen.
A: Clamp the lens at one end of a track. The clamp a
piece of white card further down the track. Set up this
equipment near a window with the lens directed at a
distant object, e.g. a nearby building – you should be
able to see an image of the object on the piece of card.
Turn off any lights in the room to make the image more
visible. Move the card along the track until the image is
focused (this is where the picture looks sharpest). When
you’ve got the best image you can, clamp the piece of
card in place so it does not move. Use a ruler to measure
the distance between the centre of the lens and the card
– this is the focal length.
A: Image formed on the
same side of the lens as the
A: The distance between the
object – a virtual image can
middle of a lens and its focal
be seen looking through the
point.
lens, it cannot be projected
onto a screen.
A: The image is real,
inverted, diminished and
found between F and 2F.
A: 1. An incident ray parallel to the axis
refracts through the lens and passes
through the focal point on the other side.
2. An incident ray passing through the
focal point before entering the lens will
refract through the lens and travel
parallel to the axis. 3. An incident ray
passing through the centre of the lens
carries on in the same direction.
A: The image is real,
inverted, magnified and
found beyond 2F.
A: The image is real,
inverted, the same size as
the object and found at 2F.
Q: Describe the image
formed by a particular
Q: How do we calculate the
converging lens when the
magnification of an image?
object is between F and the
lens.
Q: What is the function of
the objective lens of a
simple telescope?
Q: How does the eyepiece
lens of a telescope work?
Q: How does a reflecting
telescope work?
Q: What are the laws of
reflection?
Q: Why is light reflected at
a boundary?
Q: What is refraction?
A: Magnification = image
height / object height
A: The image is virtual,
upright, magnified and
found beyond F (on the
same side of the lens as the
object).
A: Rays of light from the real
image enter the eyepiece. The lens
spreads them out so they leave at
a wider angle than they entered it,
and so the light rays fill more of
your retina, making the image look
magnified.
A: It converges parallel rays
of light from a distant object
to form a real image at the
focal point of the objective
lens.
A: 1. The angle of incidence i
is equal to the angle of
reflection r (angles
measured relative to the
normal). 2. The incident ray,
reflected ray and normal lie
in the same plane.
A: A large concave mirror collects the
parallel rays of light from an object in
space. The larger mirror reflects this
light into a smaller second mirror
placed in front of the large mirror’s
focal point. The smaller mirror reflects
the light through a converging
eyepiece lens to magnify the image.
A: The bending of a wave
caused by the change in its
speed – when a light ray
travelling through air enters
a glass block it changes
direction.
A: Because of a change in
density, e.g. water is denser
than air. Whenever a wave
reaches a medium with a
different density, some of the
wave is reflected at the
boundary.
Q: Why are waves
refracted at a boundary
between two materials?
Q: What happens when
light travels from a less
dense material to a more
dense material?
Q: What happens when
light travels from a more
dense material to a less
dense material?
Q: What is a wave?
Q: What is meant by the
frequency of a wave?
Q: What is meant by the
wavelength of a wave?
Q: What is meant by the
term ‘speed’?
Q: What is what by the
amplitude of a wave?
A: It slows down, and
therefore bends towards
the normal line.
A: Refraction is caused by the
change in the speed of light at
the boundary between two
materials. The speed of light
depends on the density of the
material, e.g. it travels much
more slowly in water than air.
A: They transfer energy and
information from one place
A: It speeds up, and
to another; they create
therefore bends away from
vibrations; they do not
the normal line.
transfer matter in the
direction they are travelling.
A: Distance between
neighbouring wave peaks
(or troughs).
A: The number of vibrations
per second or number of
complete waves passing a
set point per second.
A: Maximum displacement
of a wave measured from
the mean position.
A: How fast an object travels,
calculated using the equation:
speed (metres per second) =
distance / time.
Q: Describe the features of
a transverse wave.
Q: What are some examples
of transverse waves?
Q: Describe the features of
a longitudinal wave.
Q: What are some examples
of longitudinal waves?
Q: Mathematically, what is
the relationship between
wave speed, distance and
time?
Q: Mathematically, what is
the relationship between
wave speed, wavelength and
frequency?
Q: What is the unit of
measurement of
frequency?
Q: If v = f x λ, what are the
expressions for finding f and
λ?
A: Light and all other EM
waves, seismic S waves,
waves on strings and
springs, ripples on water.
A: The vibrations are at 90o
to the direction of travel of
the wave.
A: Sound, ultrasound,
infrasound, seismic P waves,
a slinky spring when you
push and pull the end.
A: The vibrations are along
the same direction as the
wave is travelling.
A: Wave speed (metre per
second, m/s) = wavelength
(metre, m) x frequency
(hertz, Hz) (or v = f x λ).
A: Wave speed (metre per
second, m/s) = distance
(metre, m) / time (second,
s) (or v = x / t).
A: f = v / λ and λ = v / f.
A: Hertz, Hz.