Physics end of year revision

What is the definition of a wave

things that transfer energy without transferring matter

Features of longitudinal waves

direction of oscillation is parallel to the direction of energy transfer. They have compressions and rarefactions

Features of transverse waves

Direction of oscillation is parallel to the direction of energy transfer.

A wavelength is the length between two of the same points on consecutive waves.

Amplitude symbol, unit and meaning

symbol-A

unit-meters

Meaning-maximum distance from rest

Wavelength symbol, unit and meaning

Symbol- upside down y

unit-meters

Meaning- distance between 2 consecutive identical points in a wave cycle

Frequency symbol, unit and meaning

symbol-f

unit-hertz, Hz

meaning-the number of waves cycles per second

Time period symbol, unit and meaning

symbol-T

Unit-seconds

meaning-time taken for one wave cycle to pass through a point.

What is the difference between transverse and longitudinal waves?

The difference between transverse and longitudinal waves is the direction of oscillation in relation to the direction of energy transfer. In a longitudinal wave the direction of oscillation is parallel to the direction of energy transfer. In a transverse wave the direction of oscillation is perpendicular to the direction of energy transfer.

Word and symbol equation for time period

Time period(s)= 1/frequency(Hz)

T=1/f

Word and symbol equation for wave speed

Wav speed(m/s) = frequency(Hz) x Wavelength(m)

V=f x upside down y

What is a real image

formed where light rays meet

What is a virtual image

Formed where the brain incorrectly thinks light rays meet

What is a specular reflection

Image formed when light reflects off a smooth surface

What is a diffuse reflection

no image forms, light scatters off a bumpy surface

How does the angle of incidence relate to the angle of reflection

they are equal

what is the normal

a line that is always perpendicular to the reflecting surface

What happens when white light is shining on a blue object

Blue light is reflected and red and green light is absorbed because blue objects only reflect blue light.

What happens when white light is shining on a yellow object

red and green light is reflected and blue light is absorbed because yellow only reflects red and green.

What light is reflected when yellow light shines on a magenta object

Red light is reflected because magenta objects reflect red and blue. yellow contains blue and green. the green is absorbed and the red goes through.

What light is reflected when cyan light is shining on a red object

black because a red object reflects only red. cyan contains green and blue but no red so nothing is reflected.

What light goes through when white light is shone on a cyan filter

blue and green light go through because a cyan filter transmits green and blue

What light goes through when cyan light is shone on a magenta filter

Blue light goes through because a magenta filter only transmits red and blue light so the green in the cyan is absorbed and only the blue goes through.

what light is reflected when magenta light shines through a red filter and onto a blue object

• Magenta light consists of red and blue wavelengths.

• A red filter only transmits red light while absorbing other colors. So, the blue component of magenta is removed, leaving only red light to illuminate the object.

• A blue object mainly reflects blue wavelengths and absorbs other colors. Since the red filter removed the blue light, the object doesn't receive any blue to reflect.

  • Result: The blue object absorbs the red light and reflects little to no visible light, making it appear black

examples of transverse waves

Gamma rays

X-rays

Light

examples of longitudinal waves

Sound

Ultrasound

Name and describe the 8 energy stores

• Kinetic-Moving objects have energy in this store

• Thermal-Hot objects have energy in this store

• Gravitational potential-Objects that are higher up have more energy in this store

• Chemical- Energy stored in substances due to the bonds between atoms and molecules. This energy is released during chemical reactions

• Elastic potential energy-Stretched or compressed objects have energy in this store

• Electrostatic-Refers to the energy stored due to the presence of electric charges.

• Magnetic-Magnetic objects have energy in this store

• Nuclear-Energy stored in an atoms nucleus. released in nuclear reactions.

Name and describe the 4 energy transfers

• Mechanically-An object moving due to a force acting e.g. pushing, pulling, stretching

• Electrically-A charge moves through a potential difference e.g. a current flowing around a circuit

• By heating-Energy transferred from a hotter object to a colder object

• By radiation-Energy transferred by waves e.g. sound, electromagnetic

What is the equation for efficiency

Efficiency(%) = Energy transferred to useful store

Total input energy

X 100

What do Sankey diagrams do

They show how much energy is transferred usefully and how much is wasted

How can waste energy transfers be reduced

Use high quality items to reduce friction between the different objects. Use lubricant to reduce energy lost by friction. Cooling fans can be used to stop over heating.

What are the 3 rules of drawing field diagrams for magnets

• Filed lines cannot cross

• The more dense the field lines, the stronger the field

• Field lines point in the direction that a north pole feels force(N to S)

Diagram for like poles

diagram for opposite poles

uniform field diagram

like poles…

repel

opposite poles…

attract

Permanent magnets have their domains…

aligned

something non magnetic has … domains

no

Something magnetic has … domains

If I put a magnet near them then the domains will…

random, align

soft magnetic materials … their magnetism when I take away a magnet. The domains….

This is called demagnetism.

lose, un-align

Hard magnetic materials become …. magnetised.

permanently

How are the field linesdrawn in a diagram of electromagnetism

the field lines are in concentric circles that get further apart as you move further away.

Are electromagnets made of hard or soft magnets

soft magnets so the can be turned on and off

What is a common type of electromagnet

solenoid. An electromagnet arrange in a coil which has a field similar to a bar magnet

What 3 things can you do to increase the strength of an electromagnet

• Add voltage

• increase the number of coils on the solenoid

• use a coil that is made from a magnetic material

What does a dot mean on a diagram for electromagnets

that the current is coming outward towards you.

What does it mean if there is an X on a diagram for electromagnets

that the current is going into the page away from you.

What is temperature roughly a measure of

the average kinetic energy in the molecules of a substance

What is radiation

Energy transferred by EM waves such as light. The hotter an object the more radiation it emits

What types of objects are good absorbers of radiation

Dark coloured and Matte object absorb radiation well

What types of objects are bad absorbers of radiation

Light coloured and shiny objects reflect most light

What types of objects are good emitters of radiation

Dark coloured and matte objects are good emitters

What are the 3 ways of heat transfer and how do they work

• Radiation- energy transferred by EM waves such as light. the hotter and object the more radiation it emits.

• Convection-When a fluid is heated the particles gain energy causing them to move faster and collide more often. the particles move further apart and the fluid becomes less dense and it rise carrying energy with it. The cooler denser part of the fluid sinks and is then heated and the process continues. This can happen in liquid and gas.

• Conduction-The heated particle will gain energy and vibrate faster. This makes them collide with neighbouring particles and energy is transferred to the slower particles. This repeats until all particles vibrate equally.

What are the 6 ways of home insulation that we learnt about

• Cavity wall-Air gap between two layers of wall. can also have foam between the two wall layers.

• Attic insulation foam- Foam is a bad conductor, this reduces energy loss.

• Thickness of wall-The thicker the wall, the lower the rate of energy loss will be.

• Rubber seals-Go on doors and windows to block air. Warm air can’t escape so less energy is lost.

• Double glazed windows-Air gap between to layers of glass because air is a bad conductor.

• Aluminium sheeting-Reflects radiation back into the home.

What is a blackbody

A theoretical object that is a perfect emitter and absorber of radiation.

Rules for blackbody spectra

• Hot objects emit radiation across a range of wavelengths

• The hotter the object, the shorter the peak wavelength

• The hotter the object, the more radiation is emitted across all wavelengths

What is the equation for speed

speed = distance/time

V = S/T

How can you find the speed on a distance-time graph

The speed is the gradient

What does velocity mean

speed in a particular direction

What is stopping distance made up of and what is each part.

Braking distance- distance travelled while the brakes are applied

Thinking distance- distance travelled while reacting

What factors affect the braking distance

Road surface

quality of brakes

speed and mass of vehicle

What factors affect thinking distance

age

tiredness

intoxication

Describe charging by friction

When we rub objects together, the force of friction can cause electrons to be transferred from one object to another.

Describe charging by induction

A strong charge can attract or repel the electrons in another object. Even though electrons aren’t transferred to a new object, they are re-arranged causing a charge build up.