Download P1 Independent Revision Guide

P1: A revision guide
Here’s all you need to know about P1…
This may help you with your exam
questions 
Any questions…ask your Physics teacher
Topic 1
Topic 1 Visible light and the Solar
System:
1. The Solar System
2. Refracting Telescope
3. Reflecting Telescope
4. Lenses
5. Waves
The Solar System
Geocentric (Earth Centred)
Heliocentric (Sun
Centred)
Ptolemy
Copernicus
BUT Galileo discovered 4 of Jupiter’s moons, he disproved Ptolemy
completely as not everything orbited Earth!
And the ORBITS are not perfectly spherical, they are elliptical
Refraction
Light travels in straight lines. When it enters
another material it bends at an interface
(boundary).
A line at 90o to the interface is called the normal.
Changes speed and direction.
Refraction in
Lenses
Converging lenses (Convex)
focus parallel light to a
focal point (convergence).
The distance between these
is the focal length.
The fatter the lens the
shorter the focal length.
Focus light rays to a point,
form image on paper,
measure the focal length
with a ruler.
Refraction in Telescopes
The objective lens collects the light and forms an image
The eyepiece lens magnifies the image
Real and Virtual Images
A real image is the image formed where
the light rays are focussed.
A virtual image is one from which the
light rays appear to come but don’t
actually come from that image like in a
mirror.
Problems with Refractive
Telescopes
• Due to light being reflected at boundaries
the image that is processed will be fainter
• If the star is already feint it will make it
harder to detect
• Refracting telescopes need to be very long
to have a large magnification
• Large lenses help magnification but they
are heavy and difficult to mould into a
perfect shape, this means that the images
have distorted colours
Reflective Telescope
Waves Transfer Energy
TRANSVERSE: Move at right angles to the
vibration (Up and Down)
LONGITUDINAL: Move in the same
direction as the vibration (Left and Right)
Waves
FREQUENCY: The number of waves that pass a point in a
second
WAVELENGTH
Topic 2: The Electromagnetic
Spectrum
1.
2.
3.
4.
Beyond the Visible
The EM Spectrum
EM Dangers
Using EM
Radiation
5. Ionising Radiation
Wave Equations
WAVE SPEED = FREQUENCY X
WAVELENGTH
(m/s)
(Hz)
(m)
WAVE SPEED = DISTANCE / TIME
(m/s)
(m)
(s)
𝑥
𝑣=
𝑡
Herschel
Ritter
Split light with a prism,
measured the heat with
thermometers. As colours
went from violet to red the
temperatures increased.
When he placed the
thermometer just beyond
red it rose again.
He has discovered infrared.
Tried to find invisible light
beyond the violet. He shone
the light onto silver chloride.
He found that the silver
chloride turned black quicker
towards the violet end of the
spectrum. It turned black
quickest just beyond violet.
He discovered ultraviolet.
All Electromagnetic Waves are
Transverse
Can travel without any particles to vibrate
In a vacuum they all travel at the speed of light 300,000 km/s
Visible light is made out of all the colours (ROYGBIV)
Dangers of EM Radiation
All EM Waves carry energy.
At a high frequency this energy is
dangerous.
Radiowaves- No danger
Microwaves- Can internally boil blood
Infrared- Surface burns
Visible- Can cause temporary blindness
UV- Can cause skin cancer
X-Rays- Excessive exposure can cause cancer
Gamma- Mutates DNA, cancer
Uses of EM Radiation
Radio Waves- Communications, satellite, wifi
Microwaves- Microwave ovens, mobile phones
Infrared- cooking, optical fibres, thermal
imaging
Visible- human eyes, photography
UV- Security markings, disinfectant of water
X-Rays- Medical x-rays and airport scanners
Gamma- sterilise food and medical equip,
detect cancer, treat cancer in radiotherapy
Ionising Radiation
Type of
radiation
Symbol
What is
it made
from?
How far
will it
travel?
What
stops
it?
Alpha

Helium
nucleus. 2
protons &
2 neutrons
cm
Air /paper
Beta

High speed
electron
m
Aluminium
High
energy
wave
Lots of m
Thick lead
&
concrete
Gamma
γ
Alpha and Beta are not EM waves but they are ionising
particles. Like Gamma they can be extremely dangerous as
they can mutate DNA in cells
Topic 3: Waves and the Universe
1.
2.
3.
4.
5.
6.
The Universe
Spectrometers
Exploring the Universe
Alien Life?
Life-cycle of stars
Theories of the
Universe
7. Red-shift
The Universe is made out of
Everything!
Galaxies, planets, stars, nebulae, black holes etc.
Astronomers initially made observations with the naked
eye.
Galileo discovered that the Milky Way and some nebulae.
Relative sizes of the universe are hard to imagine you can
fit 30 Earths between the Earth and the Moon.
The Sun is over 11,000 ‘Earths’ away.
Spectroscopy
The light is split into the visible spectrum. Black lines show up
in the spectrum and signify what elements the star was made
from.
This kind of spectrum actually tells us the types of element
present in the outer layers of the sun (they absorb some of
the light given out by the core leaving the black lines.)
Exploring the Universe
You can use telescopes to detect different wavelengths of
the EM spectrum. However we have the problem that some
of the spectrum is absorbed by the atmosphere (for
safety).
Because of this we need to place the telescopes in space so
that the wavelengths are not absorbed.
DO NOT SAY THAT THE CLOUDS ARE IN THE WAY
OR TO BE ‘CLOSER TO THE OBJECT’ 
Earth is the only place where we know life exists
Water is ESSENTIAL to life.
Landers; land on the planet and explore the
surface
Probes; orbit the planet and photograph the
surface
Rovers; take close up photographs of the surface
We have found other planets orbiting stars but
they are too far away to produce a clear image.
Search for Extra-terrestrial Intelligence
(SETI): Analyse radio waves that have arrived at
Earth from Space for a alien message (None have
been found so far).
Life Cycle of a Star
Life Cycle of A Main Sequence Star
1. Life starts in a Nebula (a hot dense of dust & gas)
As the cloud gets more dense it starts to collapse under gravity. As
the mass gets larger, the gravitational pull does also. This creates a
protostar.
2. Eventually the temperatures rise so much that the hydrogen
atoms fuse together (fusion) to form helium and release a lot of
energy. This star then becomes a main sequence star.
3. This will remain stable for billions of years until the star stops
changing hydrogen into helium, the energy source stops and the star
begins to collapse in on itself. The outer layers expand causing a red
giant.
4. It will remain like this for another billion years before it releases
its shell of gas.
5. The rest of the star is forced together under gravity to form a
white dwarf.
6. Theoretically it is said that a white dwarf will eventually turn into
a black dwarf but no evidence of this has been shown.
Life Cycle of a Higher Mass Star
1. Stars with more mass than the Sun tend to
be hotter and burn faster
2. They fuse Hydrogen into Helium faster to
become Super Red Giants.
3. They will then supernova, where the outer
layers rapidly collapse and then explode.
4. If the star is not that massive the remains
will be a neutron star.
5. If the star is 4x more massive than the sun
it will turn into a black hole through gravity.
The gravitational pull is so strong that not
even light can escape!
Red Shift
Towards
You
Away
From You
BLUE SHIFT: the wavelength is shorter, moving towards you.
RED SHIFT: the wavelength is longer. Moving away from you,
if it is more red shift it is moving away faster and is more
likely to be further away!
Big Bang Theory
All of the Universe and matter
started out at a singular point of
concentrated energy
13.5 billion years ago.
The universe is constantly
expanding
Cosmic Microwave Background
Radiation(CMB)
Red shift
Steady State Theory
The Universe has always been
there but is expanding
New matter is constantly created
as it expands
Redshift
Topic 4: Waves and the
Earth
1. Infrasound
2.
3.
4.
5.
Ultrasound
Seismic Waves
Earthquakes
Seismometers
Infrasound
Any sound below 20Hz is known as Infra-Sound.
The human ear is not sensitive enough to detect either of these two
types of wave however many other creatures are.
Infrasound is very useful as it travels very long distances and can be
used as a method of communication between animals and a way of
detecting Earthquakes and Volcanoes.
Ultrasound
Ultrasound is frequencies above 20,000Hz( 20kHz). Some animals such
as Dolphins use ultrasound for communication.
Common uses of Ultrasound: Baby scans and SONAR devices.
The ship emits a pulse of ultrasound
This spreads out through the water and
some of it hits the sea bed.
A detector on the ship receives the echo
and the SONAR equipment detects the time
of the two.
We then calculate it using s=d/t
Remember that if you are calculating depth
or distance you need to divide it by 2!
Ultrasound in Scans
• A common use of ultrasound is to make images of babies so
that doctors can detect how well the baby is developing
• When the scan is made some of the waves are reflected
every time they enter a new medium (material).
How do plates move?
1. Convection currents in the magma (hot rises, cool
falls).
2. Friction between plates on the magma
3. Build up of energy
4. Energy is released (when they separate) in the
form of a seismic wave.
P and S waves
P or primary waves
•fastest waves
•travel through solids, liquids,
or gases
•compressional wave,
material movement is in the
same direction as wave
movement
UP and DOWN.
LONITUDINAL
S or secondary waves
•slower than P waves
•travel through solids only
•shear waves - move material
perpendicular to wave
movement
LEFT to RIGHT
TRANSVERSE
How is an Earthquake’s Epicenter Located?
By using seismic wave behavior
– P waves arrive first, then S waves
– Average speeds for all these waves is known
– After an earthquake, the difference in arrival times at a
seismograph station can be used to calculate the distance
from the seismograph to the epicenter.
– You will usually triangulate (use three stations) between
other stations, that are different distances away, to calculate
the approximate epicenter.
Seismic waves tell you about the
structure of the Earth as they
refract at boundaries with
different densities.
Topic 5: Generation and Transmission
of Electricity
1. Renewable Resources
2. Non-Renewable
Resources
3. Generating Electricity
4. Transmitting
Electricity
5. Paying for Electricity
6. Reducing Energy Use
Renewable Resources
Resource
How they work: Advantages
Disadvantages
Solar
Solar cells heat air
under glass, hot air
rises and turns gen
Have to be in a
specific area, only
works with light
Tidal
Tides move through a Direct energy transfer Have to have a tide
dam turning a turbine Predictable
Not available all year
round
Hydroelectric
Falling water in high
reservoirs
Available at any time
Started and stopped
easily
Wind
Turns a wind turbine
directly generating
electricity
Direct energy transfer Need a lot to produce
electricity
Dependant on wind
Geothermal
Heat is transferred by
hot underground
rocks
No harmful gasses
No fuel cost
Wave
Floating electrical
Direct energy transfer Not predictable
generators. Air forced
Don’t work in bad
up pipes, turns a gen
weather
Direct transfer of
energy (non-lost)
Reservoirs can dry up
Need rainfall to refill
them
Need to be by a
tectonic plate
(location)
Non-Renewable
Resources
Resource
Advantages
Coal
Formed from
fossilised plants
Oil
A carbon-based
liquid formed from
fossilised animals.
Gas
Disadvantages
Ready-made fuel. When burned they
It is relatively cheap
give off
to mine and to
atmospheric
convert into
pollutants,
energy.
including
greenhouse gases
Generating Electricity
Electromagnetic induction – creates a current in a wire
when a wire is moved into a magnetic field
The current can be increased by:
•
Using a coil of wire, or putting more turns on the
coil
•
Using an iron core inside the coil of wire
•
Using stronger magnets
•
Moving the wire faster
The direction of the current can be changed by changing
the direction:
•
Of the movement of the wire
•
Of the magnetic field
Direct current (DC) - current flows in one direction
Alternating current (AC) – current changes direction
Generators supply current with alternates in direction
(AC)
Transmitting
Electricity
A transformer
can change the size of an
alternating current
If the voltage passed through the nation grid is
increased less energy is wasted as heat and the
efficiency is improved
Power stations convert 25kV to 400kV before the
electricity is sent around the country
•A step up transformer – increases the voltage
and decreases the current.
This happens between power station and
transmission lines to stop heat being wasted.
•A step down transformer – decreases the
voltage and increases the current.
This happens between local substations and homes
to reduce the voltage for homes
POWER
The amount of energy transferred in a second.
=
X
Power = Current x Voltage
Watts(W) Amps (A) Volts (V)
=
÷
Power = Energy ÷ Time
Watts(W) Joules (J) Seconds (s)
Cost of Electricity
1000W = 1kW
Remember that with this formula you need to identify:
TIME is in HOURS
COST is in PENCE (Unless stated otherwise)
POWER is in KILOWATTS
Cost of 1 hour is in PENCE
Reducing Energy Use
Payback time= Cost / savings per year
Years
Pounds (£)
Cost Efficient means which is the best value for money
Payback time how long it will take to make the money
back in relation to savings
Topic 6: Energy Transfers
1. Energy Transfer Diagrams
2. Sankey Diagrams
3. Efficiency
4. Heat Radiation
5. The Earth’s Temperature
Energy Transfers:
how the energy is transferred to other
forms.
Types of Energy:
1. Chemical
2. Elastic Potential
3. Electrical
4. Gravitational
Potential
5. Kinetic
6. Light
7. Nuclear
8. Sound
9. Thermal
LAW OF
CONSERVATION OF
ENERGY:
ENERGY IS NEVER
CREATED OR
DESTROYED, ONLY
TRANSFERRED TO
OTHER FORMS OR
THE SURROUNDINGS
Energy Transfer Chain for a
Torch
Conservation of Energy
In physics we use the word system. This is
something in which we are studying for
changes. They can be very complex (eg, a
planet), or quite simple (eg, a piece of metal)
If you add up all the energy that has been
transferred (Output) and compare it to the
energy put in (Input), they should be the
same.
OUTPUT ENERGY = INPUT ENERGY
Sankey Diagrams:
These show energy conservation, the width
of the arrows represents the amount of
energy in joules.
Efficien
cy
How good a device is at converting energy into useful
forms is know as its efficiency.
Low energy light bulbs transfer more of the input
electrical energy, into light electricity than older light
bulbs which produce excess heat.
Efficiency
Calculation
Heat Radiation
Infrared radiation in the spectrum is heat.
ALL objects are continually absorbing and
radiating radiation.
If an object is hotter than its surroundings
it is radiating more heat than it absorbs!
COLOURS & TEXTURE:
Dark Matte surfaces absorb heat. They
also emit more radiation than bright glossy
surfaces.
Silver reflect nearly all of the heat.
The Earth’s Temperature
The Earth theoretically will try to radiate
the same amount of energy it is absorbing.
HOWEVER
Greenhouse gasses trap some of the energy
in the atmosphere so not all of it is reradiated.
This leads to (over a long period of time) an
increase in the global temperature (global
warming).
So what happens
next…?
There is only a certain amount of heat that
additional green house gasses can absorb.
1. So if the greenhouse gas emissions are stopped
that means that the temperature increase will
also stop
2. If greenhouse gasses are removed, the
temperature will decrease.
3. Scientists have came up with the idea of
putting huge white screens into space to
reflect the sunlight and shade the Earth.
Another way is to place thousands of ping pong
balls on the sea surface to do the same thing!