Year 8 Physics - Energy & Waves PDF

# PHYSICS – ENERGY & WAVES ## Year 8 Science - Mass + speed both contribute to kinetic energy - Velocity: speed + direction - Light & Sound energy cause heat energy - **Tuesday 19th November - Test** **NAME:** Sana Srivastava **MENTOR GROUP:** 8C # ENERGY ## Success Criteria: - I know that energy...

# PHYSICS – ENERGY & WAVES ## Year 8 Science - Mass + speed both contribute to kinetic energy - Velocity: speed + direction - Light & Sound energy cause heat energy - **Tuesday 19th November - Test** **NAME:** Sana Srivastava **MENTOR GROUP:** 8C # ENERGY ## Success Criteria: - I know that energy is the capacity of an object to do work. - I know that energy appears in different forms, including kinetic and potential energy. ## What is energy? **Task 1:** In pairs, brainstorm and write down the definition of energy or anything that relates to the word energy - Can’t be created or destroyed - Light - Electricity - Sound - Heat - Waves - Power - Kinetic - Friction **ENERGY** **Einstein** **Energy:** The capacity to do work, (the measurement) in joules **Movement of Energy** **Work:** The affect/response of energy happening or doing something. Energy is transferred to or from an object via a force as it displaces. - We measure energy using joules (J). The more joules something has, the more energy it has. For example, 10J is less energy than 100J. - Energy is categorized by the results (work) - Kinetic energy (high) = Temperature (hot) - Temperature = the average energy which a group of molecules have - 1J = 1,000,000 MJ - 1KJ = 1,000 KJ # TYPES OF ENERGY - There are many different types of energy, which can be placed into two different categories energy, Kinetic and Potential. ## Kinetic energy: The energy of movement ## Potential energy: Stored energy (stationary) waiting to be released **Task 2:** Categorize the below energy types as either kinetic energy or potential energy. - Heat - Light - Kinetic - Gravitational - Potential - Elastic - Potential - Chemical - Potential - Nuclear - Potential - Sound - Kinetic ## Types of Kinetic Energy - Sounds (vibration). - Electrical (movement of electrons along a wire) - Heat (jiggling of atoms) - Light (electromagnetic waves) ## Types of Potential Energy - Elastic (squishing & squashing) - Chemical (from atoms or molecules) - Gravitational (falling) - Nuclear (energy which is inside of atoms) # ENERGY HOMEWORK ## Section A: Consolidate your Understanding Use research and label the energy type with their definition. |Energy Type|Definition|Kinetic or Potential Energy?| |---|---|---| |Heat (Thermal)|The vibration and movement of molecules|Potential| |Light|Electromagnetic waves|Kinetic| |Electrical|Movement of electrons|Kinetic| |Chemical|Stored in bonds of atoms and molecules|Potential| |Nuclear|Stored in the nucleus of an atom; released when nucleus splits or combines - nucleus|Potential| |Sound|Vibration of waves through material|Kinetic| |Gravitational|Energy of position or height|Potential| |Elastic (Mechanical)|Energy stored in a material that can be stretched or compressed|Potential| ## Section B: Apply your Understanding With all the following examples, determine the type(s) of energy used. |Example|Type(s) of energy used| |---|---| |A race car travelling at maximum speed|-Sound - Heat - Gravitational (potential)| |Water falling from a waterfall before it hits the pond below|-Gravitational (potential) - Sound - Chemical (potential)| |Burning a match| - Chemical - Light - Heat - Gravitational (potential)| |A cup of hot coffee|- Heat- Gravitational (potential) - Chemical (potential)| # ENERGY TRANSFERS AND TRANSFORMATIONS ## Success Criteria: - I know that energy is conserved due to the law of conservation of energy. - I know that energy types can be transferred and transformed. ## The Law of Conservation of Energy: The Law of Conservation of Energy states: Energy cannot be created or destroyed but is converted from one form to another. This means that energy is continually changing into different forms of energy. ## Energy Transfer: **Energy Transfer:** When energy is passed from one object to another in the SAME FORM **Task 1:** Circle all the options that represent an energy transfer. - Heat → Heat - Kinetic → Kinetic - Kinetic → Heat - Light → Light - Chemical → Light - Chemical → Chemical **Task 2:** Watch the demonstration of a wind turbine. Are there any examples of energy transfer in the demonstration? If yes, what is the transfer? Kinetic energy from the first fan to the wind to the second fan occurred. ## Energy Transformation: When energy is passed from one object to another but in a DIFFERENT FORM **Task 1:** Circle all the options that represent an energy transfer. - Chemical → Kinetic - Elastic → Sound - Heat → Heat - Gravitational → Kinetic - Electrical → Light - Chemical → Chemical **Task 2:** Watch the demonstration of a wind turbine. Are there any examples of energy transformation in the demonstration? If yes, what is the transformation? Electrical energy to kinetic energy to power the first fan. Kinetic energy to electrical energy which resulted in sound energy and light energy. **Task 3:** Car engines work on a combustion reaction. Petrol is placed into a car engine as the chemical potential energy. The petrol won’t do anything until the engine burns the petrol. When the petrol is burnt it creates a gas which causes the car to begin operating. Circle the energy transformations that occur in a car. - Sound - Kinetic - Nuclear - Electrical - Heat - Light - Chemical - Gravitational - Elastic # ENERGY FLOW DIAGRAMS We can represent energy transfers and transformations using an energy flow diagram. An energy flow diagram shows the input energy form and the output energy form. **Input Energy:** The energy at the beginning of the scenarios (starting) **Output Energy:** The energy at the end of the scenario (finishing) ## PRACTICAL 1: Energy Changes **Aim:** To observe how different types of energy can cause a change. **Procedure:** Visit each of the scenarios around the room, making notes in the table below about your observations. |Scenario|Input energy type/s |Output energy type/s |Draw an energy flow diagram | |---|---|---|---| |Water turbine|Kinetic Energy - Gravitational potential energy - Chemical energy|Light energy - Sound energy – Thermal energy|Input: Kinetic, Gravitational Potential. Output: Light, Thermal, Sound, Electrical.| |Hand generator|Kinetic energy|Light energy – Sound energy – Thermal energy – Electrical energy|Input: Kinetic. Output: Light, Thermal, Sound, Electrical.| |Globe|Chemical energy|Electrical energy – Light energy – Heat energy|Input: Chemical. Output: Electrical, Light, Heat.| |Solar panel|Electrical energy|Light energy – Thermal energy - Kinetic energy|Input: Electrical. Output: Light, Thermal, Kinetic.| |Butterfly toy|Elastic potential energy|Gravitational energy - Sound energy – Kinetic energy|Input: Elastic. Output: Gravitational, Sound, Kinetic.| |Radio|Electrical energy|Sound energy - Heat/Thermal energy - Light energy|Input: Electrical. Output: Sound, Thermal, Light.| ## Discussion Questions: 1. In which situations was the initial source of energy potential? The globe and chemical potential energy whilst everything has gravitational potential energy and the butterfly had potential elastic energy. 2. Identify which energy transformation was the most complex and provide a reason for your choice. The water turbine has both kinetic energy and gravitational energy which was converted to light energy, sound energy and thermal energy. 3. Were there similarities between any of the energy changes? If so, what were they? Yes, kinetic energy was commonly converted to electrical energy. # ENERGY EFFICIENCY ## Success Criteria: - I know that most energy transformations produce useful and wasteful energy. - I am able to calculate energy efficiency. ## Energy Efficiency: **Task 1:** Restate the Law of Conservation of Energy in the box below. Energy cannot be created or destroyed, only transferred or transformed. **Energy Efficiency** Energy efficiency is measured as a percentage. The higher the percentage, the more energy efficient it is, how much energy is saved. **Energy Input:** Amount of energy at the beginning **Useful Energy Output:** The amount of energy (that we want) that comes out. Never 100%. **Task 2: ** Complete the below table by identifying the useful and wasted energy produced. |Scenario|Initial energy| Useful energy|Wasted energy| |---|---|---|---| |Using an electric toothbrush|Electrical energy|Kinetic energy|- Sound energy - Heat energy| |Playing cricket|Chemical energy (from food)|Kinetic energy|- Sound energy - Heat energy| |Using an iPhone|Chemical energy (from batteries)|Electrical energy - Sound energy| - Heat energy| |Using a torch|Chemical energy (from batteries)| - Light energy - Electrical energy| - Heat energy| # CALCULATING ENERGY EFFICIENCY Energy efficiency can be calculated using the below equation: Energy efficiency = Useful energy output / Energy input x 100 Most energy transformations are not 100% efficient and wasteful energy is produced. This wasted energy is usually released as heat energy and/or sound energy. Would you want a product with a higher or lower energy efficiency? Justify your answer. You would want a product with higher energy efficiency since you will be wasting less energy which is paid for, meaning that you lose less money whilst using the product. **Task 1:** Calculate the energy efficiency of each of the following light globes then tick the box for the light globe you would prefer to use in your home if you wanted your home to be more energy efficient. Light: 360J Heat: 3240J 3600J = 10% energy efficiency Light: 720J Heat: 2880J 3600J = 20% energy efficiency **Task 2:** Answer the following questions. For every 800 MJ of chemical energy stored in coal, 232 MJ is transformed into electrical energy, 560 MJ into heat energy, and 80 MJ into sound energy by a coal power station. Note: MJ stands for Mega-Joule which is 1000 Joules Calculate the energy efficiency of the coal power station. 1. Identify the useful form of energy - Electrical energy 2. Express this useful form as a ratio compared to the total energy input 232 : 800 = 29 MJ : 100 MJ 3. Convert this into a percentage to calculate energy efficiency 29/100 x 100 = 29% # ENERGY EFFICIENCY HOMEWORK Answer the following questions. Make sure to show your working out. **Question 1:** 100 J electrical —> 9 J light —> 91 J heat. Energy efficiency = Useful energy output / Energy input x 100 = 9/100 x 100 = 9% **Question 2:** 11 J electrical —> 9 J light —> 2 J heat Energy efficiency = Useful energy output / Energy input x 100 = 9/11 x 100 = 81.82% **Question 3:** 1400 J light —> 210 J electrical —> 1190 J heat Energy efficiency = Useful energy output / Energy input x 100 = 210/1400 x 100 = 15% **Question 4:** 1400 J light —> 1120 J useful heat —> 280 J heat loss Energy efficiency = Useful energy output / Energy input x 100 = 1120/1400 x 100 = 80% **Question 5:** A Ballista is an ancient weapon that is like a crossbow. The useful energy is the object that flies out of the ballista (projectile). 2875 J strain (projectile) —> 2500 J kinetic (ballista) + 250 J kinetic—> 120J heat + 6J sound Energy efficiency = Useful energy output / Energy input x 100 = 2750 / 2875 x 100 = 95.65% **Question 6:** A trebuchet is an ancient weapon that is like a catapult. The useful energy is the object that flies out of the trebuchet (projectile). 2875 J gravitational P.E —> 1640 J kinetic (trebuchet) + 1110 J kinetic—> 120 J heat + 5 J sound Energy efficiency = Useful energy output / Energy input x 100 = 2750 / 2875 x 100 = 95.65% **Question 7:** 35000 J chemical —> 8750 J kinetic —> 26250 J heat Energy efficiency = Useful energy output / Energy input x 100 = 8750 / 35000 x 100 = 25% **Question 8:** 35000 J chemical —> 14000 J kinetic —> 21000 J heat Energy efficiency = Useful energy output / Energy input x 100 = 14000 / 35000 x 100 = 40% **Question 9:** 3.4 MJ chemical —> 1.2 MJ electrical —> 2.2 MJ heat Energy efficiency = Useful energy output / Energy input x 100 = 1.2 / 3.4 x 100 = 35.29% **Question 10:** If there are more than one useful energy, add them together. 3.4 MJ chemical —> 1.2 MJ electrical (used) + 1.4 MJ heat (lost) + 0.8 MJ heat (lost) Energy efficiency = Useful energy output / Energy input x 100 = 2.6/3.4 x 100 = 76.47% # HEAT TRANSFERS ## Success Criteria - I know heat is usually a wasted energy in transfer and transformation. - I know the difference between convection, conduction and radiation. - I can investigate traditional fire-starting methods used by Aboriginal and Torres Strait Islander peoples and their understanding of the transformation of energy. ## What is heat? **Heat:** The transfer of kinetic energy from one object to another Heat energy is the result of the movement of tiny particles (called atoms) in solids, liquids, and gases. _vibration_. Heat energy is often released during an energy change (transfer, and transformation) and can move from one object to another. There are 3 methods of heat transfer: - Conduction - Convection - Radiation ## Conduction: **Conduction:** The transfer of heat energy between objects in contact. The hotter object transfer the vibration of particles causing it to heat the colder particles **Task 1:** Watch the conduction demonstration and fill in the below table. |Material|Time taken for dried pea to fall off (seconds)| |---|---| |Stainless steel|6 mins 16 sec| |Copper|59| |Aluminium|29| |Iron|20| |Brass|14| ## Discussion Questions: 1. Write down the materials in order of their ability to conduct heat starting from worst to best. Brass, iron, aluminium, copper, stainless steel 2. Why do the dried peas fall from the rods when the central disk is heated? Refer to particles and kinetic energy in your answer. This is because the Bunsen burner heated the central part of the conducting star, causing the particles to vibrate and gain heat. This kinetic energy is then passed from one particle to another as they collide with each other. In metals they gain heat, that around and transfer heat further and quicker as the delocalized electrons bond and cause it bond to break and the margarine particles to vibrate more intensely causing the dried peas to fall off. ## Convection **Convection:** The transfer of heat through the movement of particles in a substance - Objects do not need to be touching to be warmed by convection. They are warmed using convection currents. These currents cause hot particles to rise and cold particles to fall. - This occurs between (circle one): solid **_liquids_** gases - Examples of convection: - Hot air rising above a fire - Boiling water bubbling at the top **Task 1:** Watch the convection demonstration and fill in the below table. |Observation|Comments:| |---|---| |Predict what is going to happen to the food dye that that is in the water.|It is going to spread and the water will change to the color of the food dye| |Observe what happens to the food dye in the water.|It spread and the water changed color| **Convection Current:** - Air warms and rises - Air cools and sinks **Task 2:** Based on what you know about convection, explain why the food dye moved around in the tank during the demonstration in Task 1. The red food dye (high temperature) rose to the top of the water since the particles were vibrating faster, breaking bonds and therefore becoming less dense. However, as the particles cooled and the vibration slowed, bonds were formed once more and the substance became more dense, and moved to the bottom. ## PRACTICAL 2: Tea Bag Rockets 1. Remove the staple, label and string from the tea bag by using the scissors to cut straight across just below the staple 2. Pour out the tea into a plastic beaker 3. Unfold the tea bag and stretch it out. 4. Use your finger to open the tea bag into a cylinder. 5. Stand the cylinder on its end on the insulating heat mat. 6. Use a match to carefully ignite the top end of the tea bag (dispose of match in the solid waste container on the workbench) Based on what you know about convection, explain why the tea bags floated when lit by the match? This is because the air particles rose in temperature, started vibrating faster and produced thermal energy which broke bonds between particles and causing the gases to become less dense. This then caused the teabag to rise as the gases rose. ## RADIATION **Task 1:** Watch the radiation demonstration and fill in the below table. |Observation|Comments:| |---|---| |Tin can's initial temperature | | |Tin can's final temperature| | **Radiation:** The transfer of heat through electromagnetic waves and particles **Examples of Radiation: ** - Sun - Curium - Heat radiation can travel through a vacuum (such as space) - The heat energy travels as invisible waves and does not need to pass through any solid, liquid, or gas. # WAVES ## Success Criteria: - I know that there are two types of waves that transfer energy, mechanical and electromagnetic. - I am able to describe the motion of energy in transverse and longitudinal waves. - I am able to describe and label a wave. ## What is a wave? **Task 1:** In pairs, brainstorm and write down the definition of wave or anything that relates to the word wave. - Sound - Heat - Radiation **Wave:** The waves of energy from one place to another without an object moving Waves are an important part of everyday life. The physics of waves allows you to hear sound energy and to see the world around you (light energy). In more recent years, technological advances have used waves to create x-ray machines, broadcast radio, microwave ovens, mobile phones, and Wi-Fi. Wave motion results in the transfer of energy from one place to another without any overall movement of matter. They can be described as oscillations, or vibrations, about a rest position. For example, sound waves cause air particles to vibrate back and forth. # WAVE FEATURES **Task 1:** Complete the below table by writing the definition of each wave feature. |Wave Feature|Definition| |---|---| |Wavelength|A measure of distance between two peaks| |Amplitude|A measure of height of the wave from the middle axis| |Frequency|The number of wavelengths per second| |Crest|Top of the wave| |Trough|Bottom of the wave| **Task 2:** Label the wave features on the wave below. [Image of a wave with labels: Crest, Wavelength, Amplitude and Trough] **Task 3:** Compare the two waves in the diagram below. What relationship can you determine between the wavelength and frequency of waves? [Image of two waves comparing wavelength] The shorter the wavelength, the higher the frequency. A longer wavelength results in a lower frequency # TYPES OF WAVES There are two waves: Mechanical Waves and Electromagnetic waves. ## Mechanical Waves: Waves which need a medium (substance) in order to transfer energy. - Example: Sound waves, Water waves & Seismic waves ## Electromagnetic Waves: Energy moving without the use of particles - waves which do not need a medium (substance) to transfer energy. Can travel through a vacuum (a place without matter - particles) - Example: Visible light, radiation, radio waves, X-rays # WAVE MOTION There are two types of ways that a wave can move. ## Transverse Waves: [Diagram of a wave with the label: wave motion] Waves in which the particles move vertically (up and down) whilst the energy moves horizontally (perpendicular to the motion of particles). - Example: Water waves Direction of particle motion: Right angles to direction of energy. (up and down) ## Longitudinal Waves: [Diagram of a longitudinal wave with labels: Rarefactions, Compressions, coil movements and wave direction] The particles move left to right (longitudinally) in the same direction as the energy: - Example: Sound waves Direction of particle motion: Same direction as energy (left to right). **Task 1:** Summarise the difference between a longitudinal and transverse wave. Particles in transverse waves move perpendicular to the direction of movement and have crests and troughs. Longitudinal waves have particles which move in the same direction as the energy and have compressions and rarefactions. # WAVE MOTION HOMEWORK Answer the questions about waves. [Images - one showing a transverse wave with labels and one showing a longitudinal wave with labels] 1. What kind of wave is pictured above? - Transverse 2. Label the following on the wave above: crest, trough, wavelength, amplitude, direction of travel. 3. In what direction would the particles in this wave move, relative to the direction of wave travel? - Perpendicular 4. What kind of wave is pictured above? - Longitudinal 5. Label the following on the wave above: compression, rarefaction, wavelength, direction of travel. 6. In what direction would the particles in this wave move, relative to the direction of wave travel? - Same For each wave described below, identify the wave as more like a transverse wave or a longitudinal wave. 7. The wave created by moving the end of a spring toy up and down - Longitudinal 8. The wave created by moving the end of a spring toy back and forth parallel to the length of the spring - Transverse 9. A sound wave - Longitudinal waves 10. An ocean wave - Transverse waves 11. An electromagnetic wave - Transverse # The Electromagnetic Spectrum ## Success Criteria: - I know that the EMR spectrum has different types of radiation, including visible light. - I know that white light is made up of primary colours. ## Electromagnetic Radiation: Electromagnetic waves are created due to vibrations between electric and magnetic fields. They create a 3D wave called an electromagnetic wave. [Diagram of an electromagnetic wave with labels: Electric field, Magnetic field, Wavelength and Direction] Electromagnetic waves are fast; they travel at 300,000,000 metres per second (m/s). This is the speed of light in a vacuum. There are seven types of electromagnetic radiation. The complete range of electromagnetic radiation is called the electromagnetic spectrum as seen below. The type of electromagnetic radiation is determined by its wavelength: |Type of EMR |Wavelength| |---|---| |Gamma Ray|Shortest wavelength| |X-Ray|| |Ultraviolet|| |Visible Light|| |Infrared|| |Microwave|| |Radio|Longest wavelength| **Task 1:** Develop an acronym to remember the order of the electromagnetic spectrum. Raging Marlians Invaded Venus Using X-ray Guns - Radio waves - Microwaves - Infrared - Visible light - Ultraviolet - X-rays - Gamma rays **Task 2:** Label the electromagnetic spectrum on the previous page with the below terms. a) Shortest wavelength - Gamma ray b) Longest wavelength - Radio c) Highest frequency - Gamma ray d) Lowest frequency - Radio e) Highest energy - Gamma ray f) Lowest energy - Radio # ELECTROMAGNETIC RADIATION HOMEWORK: The differing behaviours of different forms of electromagnetic radiation make them suitable for a range of uses. With increasing frequency, electromagnetic radiation becomes progressively more hazardous. You are to describe the electromagnetic radiation; it’s uses in our everyday life, and if it is harmful. Record your findings in the table on the next page. |Type of EMR|Wavelength and Frequency|Uses |Harm | |---|---|---|---| |Radio waves|Wavelength = 1 mm - 100 km, Frequency = 3 Hz - 300 GHz, Long wavelength, low frequency|Telecommunication purposes|Increase in temperature (heating) of biological tissue)| |Microwaves|Wavelength = 1 mm - 1 m, Frequency 300 MHz - 300 GHz, Long wavelength , Low frequency|Communication, radio astronomy, remote sensing, radar, heating| Exposure to high levels = skin burns and cataracts| |Infrared|Wavelength = 780 nm - 1 mm, Frequency = 300 GHz - 400 THz, Long wavelength, Low frequency|Heat sensors, thermal imaging, night vision|Burns to the retina to blood vessels and fatty tissue, cataracts, damage to blood vessels| |Visible light|Wavelength = 380 nm - 700 nm, Frequency = 400 THz - 700 THz, Long wavelength, Low frequency|Photography and illumination, optical fibre communications, medical, astronomy, welding|Age related macular degeneration.| |Ultraviolet|Wavelength = 100 nm - 400 nm, Frequency = 7.5 x 10^14 Hz, Short wavelength High frequency|Killing bacteria, fluorescent lights, tanning beds, curing resins, sterilising|Skin cancer, eye disease, hair loss| |X-rays|Wavelength = 0.01 - 10 nm, Frequency = 3 x 10^16 Hz - 3 x 10^19 Hz, Short wavelength, High frequency|Checking for fractures, tumors, pneumonia, radiotherapy, dental radiography, medical imaging, sterilization, disinfection|Cancer risk, hair loss.| |Gamma rays|Wavelength = 10^-10 meter, Frequency = 3 x 10^19 Hz, Short wavelength, High frequency|Radiotherapy, nuclear industry, sterilization, disinfection|Cancer risk, immediate damage to cells| # VISIBLE LIGHT: Most of the electromagnetic radiation in the spectrum is invisible to us, apart from a narrow band called visible light which can be detected by the human eye. Visible light consists of all the different colours that we can see, each their own frequency and wavelength: [Diagram of the visible light spectrum with colours] **Task 1:** Describe the difference between the frequencies and wavelengths of red and violet light. Red light has the longest wavelength (620 nm - 750 nm) and the lowest frequency (430 terahertz) as well as the lowest energy. Violet light has the shortest wavelength (380 nm - 435 nm) and the highest frequency (790-690 THz) as well as the highest energy levels. When all the colours of visible light combine, they create white light. The white light can be broken into the different colours of the rainbow. When white light hits a surface, it bounces back (reflects) some colours and absorbs others (this is dependent on the chemical composition of the object itself). The colours the object reflects, is the colour you see in your eye. **Task 2:** Explain why you can see this leaf as green. [Diagram of a green leaf] The leaf absorbs all other colours of light however reflects the green light causing our eyes to perceive it as green. # REFLECTION ## Success Criteria: - I know the law of reflection. - I am able to draw an accurate ray diagram to show the reflection of light. - I know how the shape of mirrors affects the reflection of light. ## What is reflection? **Reflection:** When light hits an object and it bounces off into our eyes. ## There are two Types of Reflection: [Diagram of diffuse reflection - image is fuzzy] **Diffuse Reflection:** If the material is hitting a rough surface, then the light is scattered all over the place - image is fuzzy. [Diagram of regular reflection - image is clear.] **Regular Reflection:** If the material is hitting a smooth surface, then the light is reflected in the same direction - image is clear. **Task 1:** Looking at the diagrams on the previous page, describe how the light travels during diffuse reflection and regular reflection. Describe the difference between the 'quality' of the image that enters our eye? In a diffuse reflection light becomes scattered due to "bouncing off" an uneven surface creating a distorted and fuzzy image. A regular reflection occurs on a smooth surface where light is reflected at the same angle it hit, creating a clear image since the light is reflected at the same angle it entered at. ## Practical 1: Investigating the reflection of light **Aim:** To investigate how light reflects off a plane (flat) mirror. **Method:** 1. Place the mirror on the space below so that the reflective side is facing to the right. 2. Shine the light from the light box, so that is shines directly over the red arrow below. 3. Draw the reflected light. 4. Repeat this process for the second diagram with the blue arrow. [Diagrams of light reflecting off of a mirror with labels] ## Discussion and Analysis: 1. Using a protractor, measure the angle between the dotted line and the red arrow. 2. Using a protractor, measure the angle between the dotted line and the ray of light you drew (on the diagram with the red arrow). 3. Using a protractor, measure the angle between the dotted line and the blue arrow. 4. Using a protractor, measure the angle between the dotted line and the ray of light you drew (on the diagram with the blue arrow). 5. What do you notice about the two angles in each of the situations? 6. What can you conclude about the relationship between the angles of the light beams? ## Law of Reflection: [Diagram of the law of reflection] **Incident Ray:** Light which hits the surface **Reflected Ray:** Reflected light which has bounced off the surface! **The Normal:** An imaginary line which runs perpendicular to the mirror. **Angle of Incidence:** The angle the light hits the surface (between the normal and the ray) **Angle of Reflection:** The angle the light is reflected at (between the normal and the reflected ray) **Task 1:** Write the Law of Reflection in the box below: Angle of incidence = Angle of reflection **Task 2:** Determine the angle of incidence or reflection in the examples below: a) What is the angle of incidence? - 80 degrees b) What is the angle of reflection? - 40 degrees c) What is the angle of incidence? - 55 degrees ## Non-Planar Mirrors: Mirrors can be flat (planar), but they can also be curved. Mirrors can be curved either inwards or outwards. **Task 1:** Grab a spoon and look at your reflection in both sides. What happened to your reflection when you had the spoon bulging inwards? The image appears taller and thinner, upside down. This is because the spoon's surface bounces rays back at an angle. The rays from the upper part are reflected downwards, and vice versa. The rays from the central point pass this point straight, hence, the central part appears to be at the same place - hence, the center of the image appears larger. What happened to your reflection when you had the spoon bulging outwards? The image appeared shorter and wider, as well as magnified. Light beams outwards and wide –spread. ## Convex Mirror: Bulge outwards, light becomes outwards and wide –spread. Makes the image appear shorter and wider. Example: Road mirror ## Concave Mirror: Bulge inwards, light becomes reflected into a central point, makes the image appear taller and thinner Example: Spoon **Task 2:** In the boxes below, draw a concave and a convex mirror. [Diagrams of Concave and Convex mirrors] **Task 2:** Describe the difference between the reflected light of the convex and concave mirrors. Include a statement about the size of the image each produces. ## Mammalian Eye - Reacts to light and pressure allowing vision to occur. - Specialized cells identify depth, motion, and color. - **Sclera** - Thick white, dense material which protects the eye - opaque (a tissue) - **Cornea:** - A rough convex outer coat which refracts light into lens-- translucent. - **Pupil:** - An opening in the front of the eye (behind the cornea), which allows light to enter the eye. - **Iris:** - A series of muscles pigmented in color, which expand and contract to control the size of the pupil. **Lens:** - A transparent convex, pliable disk attached to the ciliary muscles - tough, jelly-like substance **Ciliary Muscles:** - The muscles that control the size of the lens which focuses light onto the retina. **Retina:** - The lining on the rods and cones which has around 130 million light sensitive cells, there are two types - rods, which are more sensitive to light whilst cones detect colors. Rods are more sensitive than cones. The rods and cones then send the signal to the optic nerve which then gets sent to the brain for processing. - **Macula:** - A central area from the object you are focusing on. - **Optic Nerve:** - A bundle of sensory neurons which transmit the electrical message from the eye to the brain. - **Vitreous Humor:** - A clear, jelly-like substance which fills the space between the lens and the retina. It helps to hold the spherical shape of the eye and keeps the retina in place through the pressure. - **Retina** creates an image which is upside down.