4.2.16

Half Lives

Test yourself on Half Lives

Test your knowledge with free interactive questions on Seneca — used by over 10 million students.

Half-Lives

The half-life is the average time taken for the number of radioactive nuclei to halve. The activity of a radioactive substance is measured in Becquerels (Bq).

Predicting half-lives

Predicting half-lives

The radioactive decay of an individual atom is random and unpredictable.
However, large groups of nuclei do normally behave in predictable ways.

Constant half-lives

Constant half-lives

The half-life is the average time taken for the number of radioactive nuclei to halve.
The half-life for any isotope of an element is constant.
The half-life of unstable isotopes can be seconds or millions of years.

Measuring half-lives

Measuring half-lives

To find the half-life of an isotope from a graph or table,
Measure the time that it takes for the radioactive count rate or the number of unstable nuclei to halve.

Background radiation

Background radiation

To find the half-life of a radioactive isotope, we must strip out the background radiation of the environment around us.
The equation for calculating substance radiation is:
- Substance radiation = total radiation − background radiation

Measuring background radiation

Measuring background radiation

We can measure the level of background radiation using a Geiger counter.

1

Energy

1.1

Energy Changes

1.2

Energy Losses & Efficiency

1.2.1Energy Wastage 1.2.2Energy Efficiency 1.2.3Reducing Energy Loss 1.2.4Power & Energy Transfer 1.2.5Required Practical - Investigating Insulation 1.2.6Efficiency - Calculations 1.2.7Grade 9 - Energy & Efficiency

1.3

Energy Resources

1.3.1Energy Resources 1.3.2Fossil Fuels 1.3.3Geothermal Energy 1.3.4Wind Energy 1.3.5Water Energy 1.3.6Tidal Energy 1.3.7Nuclear Energy 1.3.8Solar Energy 1.3.9Original Source of Energy 1.3.10Non-Renewable & Renewable Resources 1.3.11Uses of Energy Sources 1.3.12Changing Electricity Use 1.3.13Renewable Energy 1.3.14Limits to Renewable Energy Resources 1.3.15End of Topic Test - Energy 1.3.16Exam-Style Questions - Energy

2

Electricity

2.1

Electric Charge

2.1.1Circuit Diagrams 2.1.2Circuit Symbols 2.1.3Current 2.1.4Current Equation 2.1.5Current - Calculations 2.1.6Conductors 2.1.7Electrical Conductors - Electrons 2.1.8Potential Difference 2.1.9Voltage Equation 2.1.10Measurements in Circuit 2.1.11Voltage - Calculations 2.1.12Diagnostic Misconceptions - Powering a Circuit

2.2

Resistance & Electrical Work

2.2.1Resistance 2.2.2Measuring Resistance 2.2.3Resistance Graph 2.2.4Diodes 2.2.5LDRs & Thermistors 2.2.6Electrical Work 2.2.7Power 2.2.8Ohm's Law 2.2.9Ohm's Law - Equation 2.2.10Resistance & Ohms Law - Calculations 2.2.11Electrical Work - Calculations 2.2.12Required Practical - Investigating Resistance

2.3

Electric Circuits

2.3.1Series Circuits 2.3.2Resistors 2.3.3Required Practical - I–V Characteristics 2.3.4Cells in Series 2.3.5Series Circuits - Calculations 2.3.6Parallel Circuits 2.3.7Parallel Current 2.3.8Parallel Resistance 2.3.9Lights in Parallel 2.3.10Parallel Circuits - Calculations 2.3.11Grade 9 - Circuits 2.3.12Exam-Style Questions - Electricity

2.4

Electricity in Homes

2.4.1AC/DC 2.4.2Mains Electricity 2.4.3Power Ratings 2.4.4National Grid 2.4.5Domestic Uses - Calculations 2.4.6Fuses & Circuit Breakers 2.4.7Fuse Ratings 2.4.8Earthing 2.4.9Dangers of the Live Wire 2.4.10End of Topic Test - Electricity

2.5

Static Electricity

2.5.1Electrical Charge 2.5.2Charging an Object 2.5.3Charged Objects 2.5.4Static Electricity 2.5.5Electric Fields 2.5.6Field Diagrams

3

Particle Model of Matter

3.1

States of Matter

3.1.1Atomic Model 3.1.2Atomic Structure 3.1.3Sub-Atomic Particles 3.1.4Models of the Atom 3.1.5Alpha Particles 3.1.6Electron Arrangements 3.1.7Density 3.1.8Density Equation 3.1.9Density & the Particle Model 3.1.10Density - Calculations 3.1.11Changes of State 3.1.12Melting & Boiling 3.1.13Exam-Style Questions - Density 3.1.14Required Practical - Density 3.1.15Diagnostic Misconceptions - Floating 3.1.16Diagnostic Misconceptions - Volume

3.2

Heat

3.2.1Internal Energy 3.2.2Change in Thermal Energy 3.2.3Required Practical - Specific Heat Capacity 3.2.4Equation for Heat Capacity 3.2.5Leslie's Cube 3.2.6Internal Energy - Calculations 3.2.7Melting & Boiling 3.2.8Latent Heat 3.2.9Energy Change for Change of State 3.2.10Latent Heat - Calculations 3.2.11Specific Latent Heat of Fusion 3.2.12Specific Latent Heat of Vaporisation

3.3

Particle Motion in Gases

3.3.1States of Matter 3.3.2Properties of Gases 3.3.3Temperature Increase in a Gas 3.3.4Work Done on a Gas 3.3.5End of Topic Test - Particle Model of Matter 3.3.6Grade 9 - Particle Model of Matter 3.3.7Exam-Style Questions - Specific Heat Capacity

4

Atoms & Radiation

4.1

Atoms

4.1.1Atomic Model 4.1.2Structure of an Atom 4.1.3Sub-Atomic Particles 4.1.4Alpha Particles 4.1.5The Model of the Atom 4.1.6Electron Arrangements 4.1.7Proton & Nucleon Numbers 4.1.8Atoms & Ions 4.1.9Isotopes 1 4.1.10Isotopes 2 4.1.11Carbon Nuclides 4.1.12Exam-Style Questions - Atomic Structure 4.1.13Diagnostic Misconceptions - Types of Radiation

4.2

Radiation

5

Forces

5.1

Basics of Motion

5.1.1Velocity 5.1.2Average Speed 5.1.3Adding Vectors 5.1.4Acceleration 5.1.5Distance vs Displacement 5.1.6Contact & Non-Contact Forces 5.1.7Contact Forces - Examples 5.1.8Distance-Time Graphs 5.1.9Speed-Time Graphs 5.1.10Velocity - Time Graph 5.1.11Average Speed - Calculations 5.1.12Acceleration - Calculations 5.1.13Uniform Acceleration - Calculations 5.1.14Grade 9 - Motion 5.1.15Exam-Style Questions - Motion 5.1.16Diagnostic Misconception - Motion 5.1.17Diagnostic Misconceptions - Acceleration

5.2

Forces

5.3

Effects of Forces

5.4

Pressure

5.4.1Pressure & Force on Container 5.4.2Atmospheric Pressure 5.4.3Liquid Pressure 5.4.4Pressure - Calculations 5.4.5Liquid Pressure - Calculations 5.4.6Upthrust 5.4.7Depth Control of Submarine 5.4.8Pressure Difference 5.4.9End of Topic Test - Forces 5.4.10Exam-Style Questions - Pressure

6

Waves

6.1

Wave Basics

6.1.1Wave Basics 6.1.2Wave Speed Formula 6.1.3Wave Speed Equation 6.1.4Wave Speed - Calculations 6.1.5Wave Frequency Formula 6.1.6Wavelength & Amplitude 6.1.7Wave Frequency - Calculations 6.1.8Transverse Waves 6.1.9Longitudinal Wave 6.1.10Required Practical - Ripple Tank 6.1.11Diagnostic Misconceptions - Wavelength

6.2

Waves at a Boundary

6.2.1Waves at a Boundary 6.2.2Waves at a Boundary 2 6.2.3Reflection of Light 6.2.4Refraction of Light 6.2.5Refraction of Light 2 6.2.6Internal Reflection 6.2.7Required Practical - Reflection and Refraction

6.3

Sound Waves

6.3.1Sound Waves 6.3.2Sound Waves & our Ears 6.3.3Speed of Sound 1 6.3.4Speed of Sound 2 6.3.5Sound as a Wave 6.3.6Uses of Sound Waves: Ultrasound Waves 6.3.7Uses of Sound Waves: Earthquakes 6.3.8Sound Waves - Calculations 6.3.9End of Topic Test - Introduction to Waves 6.3.10Exam-Style Questions - Wave Speed

6.4

Electromagnetic Waves

6.4.1Properties of Electromagnetic Waves 6.4.2Gamma Rays 6.4.3X-Rays 6.4.4UV Light 6.4.5Infrared Radiation 6.4.6Microwaves 6.4.7Radio Waves 6.4.8Properties 2 6.4.9Visible Light 6.4.10Visible Light 2 6.4.11Specular & Diffuse Reflection 6.4.12Colours 6.4.13Grade 9 - Waves

6.5

Lenses

6.5.1Lenses 6.5.2Convex Lens 6.5.3Concave Lens 6.5.4Lenses - Calculations 6.5.5Images 6.5.6Ray Diagrams 6.5.7Ray Diagrams 2

6.6

Heat & Radiation

6.6.1Infrared Radiation 6.6.2Radiation & Surface Colour 6.6.3Surface Area & Temperature 6.6.4Temperature 6.6.5Absorption & Emission 6.6.6Greenhouse Effect 6.6.7Energy Balance of the Earth 6.6.8End of Topic Test - EM Waves, Lenses & Heat 6.6.9Exam-Style Questions - EM Radiation

7

Magnetism

7.1

Magnetism Basics

7.1.1Magnetism 7.1.2Magnetic Materials 7.1.3Induced Magnetism 7.1.4Magnetic Fields 7.1.5Magnetic Field Patterns

7.2

Electromagnetism

7.2.1The Magnetic Effect of a Current 7.2.2Solenoid Field 7.2.3Magnetic Field Strength 7.2.4Uses of Electromagnets 7.2.5Motor Effect 7.2.6Direction of Motor Effect 7.2.7Magnetic Flux Equation 7.2.8Magnetic Flux - Calculations 7.2.9Electric Motors 7.2.10Loudspeakers 7.2.11Force Acting on a Coil in a Magnetic Field 7.2.12Induced Potential Difference 7.2.13Increasing the Induced Potential Difference 7.2.14Magnetic Field Direction 7.2.15Forces Between Electricity & Magnets 7.2.16AC/DC 7.2.17AC Generators 7.2.18Generator Effect 7.2.19Microphones

7.3

Transformers

7.3.1Transformers 7.3.2Transformer Equation 7.3.3Step-Up & Step-Down Transformers 7.3.4Principles of Transformer Operation 7.3.5High-Voltage Transmission & Transformers 7.3.6Energy in Transformers 7.3.7Power Losses in Cables 7.3.8Transformers - Calculations 7.3.9Transformers 2 - Calculations 7.3.10End of Topic Test - Magnetism 7.3.11Grade 9 - Transformers 7.3.12Exam-Style Questions - Magnetic Fields

8

Astrophysics

8.1

Astrophysics

8.1.1The Solar System 8.1.2The Sun 8.1.3The Solar System - Calculations 8.1.4Orbits 8.1.5Stable Orbits 8.1.6Orbits HyperLearning 8.1.7Life Cycle of a Star like the Sun 8.1.8Life Cycle of a Star Much Bigger than the Sun 8.1.9Creation of Elements 8.1.10Red-shift 8.1.11The Big Bang Theory 8.1.12Gaps in Knowledge 8.1.13End of Topic Test - Astrophysics 8.1.14Exam-Style Questions - Astrophysics

Jump to other topics

1

Energy

1.1

Energy Changes

1.2

Energy Losses & Efficiency

1.2.1Energy Wastage 1.2.2Energy Efficiency 1.2.3Reducing Energy Loss 1.2.4Power & Energy Transfer 1.2.5Required Practical - Investigating Insulation 1.2.6Efficiency - Calculations 1.2.7Grade 9 - Energy & Efficiency

1.3

Energy Resources

1.3.1Energy Resources 1.3.2Fossil Fuels 1.3.3Geothermal Energy 1.3.4Wind Energy 1.3.5Water Energy 1.3.6Tidal Energy 1.3.7Nuclear Energy 1.3.8Solar Energy 1.3.9Original Source of Energy 1.3.10Non-Renewable & Renewable Resources 1.3.11Uses of Energy Sources 1.3.12Changing Electricity Use 1.3.13Renewable Energy 1.3.14Limits to Renewable Energy Resources 1.3.15End of Topic Test - Energy 1.3.16Exam-Style Questions - Energy

2

Electricity

2.1

Electric Charge

2.1.1Circuit Diagrams 2.1.2Circuit Symbols 2.1.3Current 2.1.4Current Equation 2.1.5Current - Calculations 2.1.6Conductors 2.1.7Electrical Conductors - Electrons 2.1.8Potential Difference 2.1.9Voltage Equation 2.1.10Measurements in Circuit 2.1.11Voltage - Calculations 2.1.12Diagnostic Misconceptions - Powering a Circuit

2.2

Resistance & Electrical Work

2.2.1Resistance 2.2.2Measuring Resistance 2.2.3Resistance Graph 2.2.4Diodes 2.2.5LDRs & Thermistors 2.2.6Electrical Work 2.2.7Power 2.2.8Ohm's Law 2.2.9Ohm's Law - Equation 2.2.10Resistance & Ohms Law - Calculations 2.2.11Electrical Work - Calculations 2.2.12Required Practical - Investigating Resistance

2.3

Electric Circuits

2.3.1Series Circuits 2.3.2Resistors 2.3.3Required Practical - I–V Characteristics 2.3.4Cells in Series 2.3.5Series Circuits - Calculations 2.3.6Parallel Circuits 2.3.7Parallel Current 2.3.8Parallel Resistance 2.3.9Lights in Parallel 2.3.10Parallel Circuits - Calculations 2.3.11Grade 9 - Circuits 2.3.12Exam-Style Questions - Electricity

2.4

Electricity in Homes

2.4.1AC/DC 2.4.2Mains Electricity 2.4.3Power Ratings 2.4.4National Grid 2.4.5Domestic Uses - Calculations 2.4.6Fuses & Circuit Breakers 2.4.7Fuse Ratings 2.4.8Earthing 2.4.9Dangers of the Live Wire 2.4.10End of Topic Test - Electricity

2.5

Static Electricity

2.5.1Electrical Charge 2.5.2Charging an Object 2.5.3Charged Objects 2.5.4Static Electricity 2.5.5Electric Fields 2.5.6Field Diagrams

3

Particle Model of Matter

3.1

States of Matter

3.1.1Atomic Model 3.1.2Atomic Structure 3.1.3Sub-Atomic Particles 3.1.4Models of the Atom 3.1.5Alpha Particles 3.1.6Electron Arrangements 3.1.7Density 3.1.8Density Equation 3.1.9Density & the Particle Model 3.1.10Density - Calculations 3.1.11Changes of State 3.1.12Melting & Boiling 3.1.13Exam-Style Questions - Density 3.1.14Required Practical - Density 3.1.15Diagnostic Misconceptions - Floating 3.1.16Diagnostic Misconceptions - Volume

3.2

Heat

3.2.1Internal Energy 3.2.2Change in Thermal Energy 3.2.3Required Practical - Specific Heat Capacity 3.2.4Equation for Heat Capacity 3.2.5Leslie's Cube 3.2.6Internal Energy - Calculations 3.2.7Melting & Boiling 3.2.8Latent Heat 3.2.9Energy Change for Change of State 3.2.10Latent Heat - Calculations 3.2.11Specific Latent Heat of Fusion 3.2.12Specific Latent Heat of Vaporisation

3.3

Particle Motion in Gases

3.3.1States of Matter 3.3.2Properties of Gases 3.3.3Temperature Increase in a Gas 3.3.4Work Done on a Gas 3.3.5End of Topic Test - Particle Model of Matter 3.3.6Grade 9 - Particle Model of Matter 3.3.7Exam-Style Questions - Specific Heat Capacity

4

Atoms & Radiation

4.1

Atoms

4.1.1Atomic Model 4.1.2Structure of an Atom 4.1.3Sub-Atomic Particles 4.1.4Alpha Particles 4.1.5The Model of the Atom 4.1.6Electron Arrangements 4.1.7Proton & Nucleon Numbers 4.1.8Atoms & Ions 4.1.9Isotopes 1 4.1.10Isotopes 2 4.1.11Carbon Nuclides 4.1.12Exam-Style Questions - Atomic Structure 4.1.13Diagnostic Misconceptions - Types of Radiation

4.2

Radiation

5

Forces

5.1

Basics of Motion

5.1.1Velocity 5.1.2Average Speed 5.1.3Adding Vectors 5.1.4Acceleration 5.1.5Distance vs Displacement 5.1.6Contact & Non-Contact Forces 5.1.7Contact Forces - Examples 5.1.8Distance-Time Graphs 5.1.9Speed-Time Graphs 5.1.10Velocity - Time Graph 5.1.11Average Speed - Calculations 5.1.12Acceleration - Calculations 5.1.13Uniform Acceleration - Calculations 5.1.14Grade 9 - Motion 5.1.15Exam-Style Questions - Motion 5.1.16Diagnostic Misconception - Motion 5.1.17Diagnostic Misconceptions - Acceleration

5.2

Forces

5.3

Effects of Forces

5.4

Pressure

5.4.1Pressure & Force on Container 5.4.2Atmospheric Pressure 5.4.3Liquid Pressure 5.4.4Pressure - Calculations 5.4.5Liquid Pressure - Calculations 5.4.6Upthrust 5.4.7Depth Control of Submarine 5.4.8Pressure Difference 5.4.9End of Topic Test - Forces 5.4.10Exam-Style Questions - Pressure

6

Waves

6.1

Wave Basics

6.1.1Wave Basics 6.1.2Wave Speed Formula 6.1.3Wave Speed Equation 6.1.4Wave Speed - Calculations 6.1.5Wave Frequency Formula 6.1.6Wavelength & Amplitude 6.1.7Wave Frequency - Calculations 6.1.8Transverse Waves 6.1.9Longitudinal Wave 6.1.10Required Practical - Ripple Tank 6.1.11Diagnostic Misconceptions - Wavelength

6.2

Waves at a Boundary

6.2.1Waves at a Boundary 6.2.2Waves at a Boundary 2 6.2.3Reflection of Light 6.2.4Refraction of Light 6.2.5Refraction of Light 2 6.2.6Internal Reflection 6.2.7Required Practical - Reflection and Refraction

6.3

Sound Waves

6.3.1Sound Waves 6.3.2Sound Waves & our Ears 6.3.3Speed of Sound 1 6.3.4Speed of Sound 2 6.3.5Sound as a Wave 6.3.6Uses of Sound Waves: Ultrasound Waves 6.3.7Uses of Sound Waves: Earthquakes 6.3.8Sound Waves - Calculations 6.3.9End of Topic Test - Introduction to Waves 6.3.10Exam-Style Questions - Wave Speed

6.4

Electromagnetic Waves

6.4.1Properties of Electromagnetic Waves 6.4.2Gamma Rays 6.4.3X-Rays 6.4.4UV Light 6.4.5Infrared Radiation 6.4.6Microwaves 6.4.7Radio Waves 6.4.8Properties 2 6.4.9Visible Light 6.4.10Visible Light 2 6.4.11Specular & Diffuse Reflection 6.4.12Colours 6.4.13Grade 9 - Waves

6.5

Lenses

6.5.1Lenses 6.5.2Convex Lens 6.5.3Concave Lens 6.5.4Lenses - Calculations 6.5.5Images 6.5.6Ray Diagrams 6.5.7Ray Diagrams 2

6.6

Heat & Radiation

6.6.1Infrared Radiation 6.6.2Radiation & Surface Colour 6.6.3Surface Area & Temperature 6.6.4Temperature 6.6.5Absorption & Emission 6.6.6Greenhouse Effect 6.6.7Energy Balance of the Earth 6.6.8End of Topic Test - EM Waves, Lenses & Heat 6.6.9Exam-Style Questions - EM Radiation

7

Magnetism

7.1

Magnetism Basics

7.1.1Magnetism 7.1.2Magnetic Materials 7.1.3Induced Magnetism 7.1.4Magnetic Fields 7.1.5Magnetic Field Patterns

7.2

Electromagnetism

7.2.1The Magnetic Effect of a Current 7.2.2Solenoid Field 7.2.3Magnetic Field Strength 7.2.4Uses of Electromagnets 7.2.5Motor Effect 7.2.6Direction of Motor Effect 7.2.7Magnetic Flux Equation 7.2.8Magnetic Flux - Calculations 7.2.9Electric Motors 7.2.10Loudspeakers 7.2.11Force Acting on a Coil in a Magnetic Field 7.2.12Induced Potential Difference 7.2.13Increasing the Induced Potential Difference 7.2.14Magnetic Field Direction 7.2.15Forces Between Electricity & Magnets 7.2.16AC/DC 7.2.17AC Generators 7.2.18Generator Effect 7.2.19Microphones

7.3

Transformers

7.3.1Transformers 7.3.2Transformer Equation 7.3.3Step-Up & Step-Down Transformers 7.3.4Principles of Transformer Operation 7.3.5High-Voltage Transmission & Transformers 7.3.6Energy in Transformers 7.3.7Power Losses in Cables 7.3.8Transformers - Calculations 7.3.9Transformers 2 - Calculations 7.3.10End of Topic Test - Magnetism 7.3.11Grade 9 - Transformers 7.3.12Exam-Style Questions - Magnetic Fields

8

Astrophysics

8.1

Astrophysics

8.1.1The Solar System 8.1.2The Sun 8.1.3The Solar System - Calculations 8.1.4Orbits 8.1.5Stable Orbits 8.1.6Orbits HyperLearning 8.1.7Life Cycle of a Star like the Sun 8.1.8Life Cycle of a Star Much Bigger than the Sun 8.1.9Creation of Elements 8.1.10Red-shift 8.1.11The Big Bang Theory 8.1.12Gaps in Knowledge 8.1.13End of Topic Test - Astrophysics 8.1.14Exam-Style Questions - Astrophysics

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Fission & Fusion Equations

Measuring Half Lives