Force and Energy

Curved Mirrors - Types of curved mirrors: concave, convex and parabolic
Curved Mirrors - Terms used in curved mirrors: concave mirror
Curved Mirrors - Terms used in curved mirrors: convex mirror and focal length

By the end of the lesson, the learner should be able to:

- Identify and distinguish between concave, convex and parabolic curved mirrors
- Describe the three types of curved mirrors based on the direction their reflecting surfaces curve
- Show interest in observing curved mirrors in the everyday environment

- Define and identify terms associated with a convex mirror: pole, principal axis, centre of curvature, principal focus and focal length
- Determine the focal length of a concave mirror experimentally and calculate the radius of curvature
- Show interest in using experimental methods to determine the properties of curved mirrors

In groups, learners are guided to:
- Study pictures of different types of mirrors and identify which represent curved mirrors; discuss the meaning of a curved mirror
- Use mirrors provided by the teacher to identify concave mirrors (surface curved inwards, converging) and convex mirrors (surface curved outwards, diverging)
- Discuss parabolic surfaces: ability to converge or diverge all incident light rays at the focal point (Figures 3.1–3.3)
- Draw a convex mirror diagram (radius 3 cm): label C (behind mirror), principal axis, P, construct perpendicular bisector of CP and label F; note that C and F are behind the mirror for a convex mirror
- Set up the focal length experiment: place a concave mirror on a stand facing a distant object; move a white screen until a sharp inverted image forms; measure and record the distance between the mirror and the screen (Table 3.1); repeat three times and calculate the average focal length
- Solve the worked example: mirror gives sharp image at 22 cm — state the focal length and calculate the radius of curvature

What is a curved mirror and how do the three types differ in the direction of their reflecting surfaces?
How is the focal length of a concave mirror determined experimentally and how does it relate to the radius of curvature?

- Spotlight Integrated Science pg. 129
- Different types of mirrors, charts of mirror types
- Reference books
- Spotlight Integrated Science pg. 131
- Pencil, ruler, compass, plain paper, reference books
- Digital resources
- Spotlight Integrated Science pg. 132
- Concave mirror, metre rule, white screen, mirror holder, distant object
- Reference books

- Observation - Oral questions - Written assignments

Force and Energy

Curved Mirrors - Rules of reflection: three special rays

By the end of the lesson, the learner should be able to:

- State and apply the three rules of reflection for curved mirrors: ray parallel to principal axis, ray through centre of curvature, ray through principal focus
- Draw ray diagrams showing each rule for both concave and convex mirrors
- Appreciate that predictable ray behaviour is the foundation for locating images in curved mirrors

In groups, learners are guided to:
- Investigate Ray 1: draw a ray parallel and close to the principal axis; show it reflects through F (concave) or appears to diverge from F (convex) — Figures 3.10 and 3.11
- Investigate Ray 2: draw a ray through C; show it reflects back along the same path in a concave mirror; show it appears to come from C as a broken line in a convex mirror — Figures 3.14 and 3.15
- Investigate Ray 3: draw a ray through F (concave) or appearing to pass through F (convex); show it reflects parallel to the principal axis — Figures 3.16–3.18

How does knowing how three special rays behave after reflection allow us to locate any image formed by a curved mirror?

- Spotlight Integrated Science pg. 135
- Pencil, 30 cm ruler, plain paper, exercise book
- Charts of ray diagrams (Figures 3.10–3.18)

- Observation - Written assignments - Oral questions

Force and Energy

Curved Mirrors - Image location: object beyond C and object at C
Curved Mirrors - Image location: object between C and F, and object at F

By the end of the lesson, the learner should be able to:

- Draw ray diagrams to locate the image formed when an object is placed beyond C in a concave mirror
- Draw ray diagrams to locate the image formed when an object is placed at C in a concave mirror
- State the characteristics of the image formed in each case

In groups, learners are guided to:
- Draw Figure 3.20 (object beyond C): use Ray 1 (parallel → through F) and Ray 2 (through F → parallel); locate intersection; state characteristics: image between C and F, real, inverted, smaller than object
- Draw Figure 3.22 (object at C): apply the same two rays; locate intersection at C; state characteristics: image at C, real, inverted, same size as object
- Discuss why the image moves closer to F as the object moves farther from C; share and compare diagrams with classmates

What happens to the image of an object in a concave mirror as the object moves from beyond C to exactly at C?

- Spotlight Integrated Science pg. 140
- Pencil, 30 cm ruler, plain paper, exercise book
- Charts of ray diagrams
- Spotlight Integrated Science pg. 145

- Observation - Written assignments - Oral questions

Force and Energy

Curved Mirrors - Image location: object between F and P, and convex mirror

By the end of the lesson, the learner should be able to:

- Draw ray diagrams to locate the image when an object is placed between F and P in a concave mirror
- Draw ray diagrams to locate images formed by a convex mirror for any object position
- Distinguish between real and virtual images in curved mirrors

In groups, learners are guided to:
- Draw Figure 3.28 (object between F and P): extend reflected rays behind mirror with dotted lines; locate virtual intersection behind mirror; state characteristics: virtual, behind mirror, upright, larger than object
- Draw Figure 3.35 (convex mirror): use Ray 1 (parallel → appears from F) and Ray 3 (appears through C → reflected back); extend dotted virtual rays behind mirror; state characteristics: virtual, between P and F, upright, smaller than object (Figure 3.38)
- Discuss: concave mirrors can form both real and virtual images depending on object position; convex mirrors always form virtual images

How does the position of an object in front of a concave mirror determine whether the image formed is real or virtual?

- Spotlight Integrated Science pg. 148
- Pencil, 30 cm ruler, plain paper, exercise book
- Charts of ray diagrams

- Observation - Written assignments - Oral questions

Force and Energy

Curved Mirrors - Practical: characteristics of images in a concave mirror
Curved Mirrors - Applications of curved mirrors in day-to-day life

By the end of the lesson, the learner should be able to:

- Investigate experimentally the characteristics of images formed by a concave mirror when an object is placed at various positions
- Record and interpret observations of image size, nature (real/virtual) and orientation at each object position
- Appreciate that systematic experimentation confirms the predictions made from ray diagrams

- Describe the broader applications of curved mirrors including solar cookers, projector lamps and road safety devices
- Solve structured problems on curved mirrors involving image position and characteristics
- Appreciate the wide range of practical applications of curved mirrors in modern life

In groups, learners are guided to:
- Set up the practical (Figure 3.42): concave mirror on stand, mark C and F on a metre rule; place a lit candle beyond C; adjust screen until sharp image forms; observe and record size (smaller), nature (real) and orientation (inverted)
- Repeat for object at C (same size, real, inverted), between C and F (larger, real, inverted); note that no image forms on screen when object is at F or between F and P
- Discuss results and confirm they match the predictions from ray diagrams; complete a summary table of all object positions and corresponding image characteristics
- Read the journal excerpt (Therono's solar cooker) and write personal ways curved mirrors are used in daily life; present findings to the class
- Solve structured questions from the assessment activity: label parts of concave and convex mirror diagrams; explain the importance of a driving mirror; answer the magic mirror question (top to bottom: convex → plane → concave); explain why headlights use concave reflectors; describe characteristics of the image Winnie saw in the motorcycle side mirror
- Discuss: using knowledge of mirrors, design a simple solar cooker at home with guidance from a parent or guardian

How does experiment confirm what ray diagram theory predicts about image formation in a concave mirror?
How can knowledge of curved mirrors be applied to solve real-life engineering and safety problems?

- Spotlight Integrated Science pg. 152
- Concave mirror with known focal length, candle, lighter, screen, metre rule, mirror holder
- Reference books
- Spotlight Integrated Science pg. 155
- Reference books
- Digital resources

- Observation - Written assignments - Oral questions
- Written tests - Oral questions - Observation

Force and Energy

Waves - Meaning of waves and generation using a slinky spring

By the end of the lesson, the learner should be able to:

- Define a wave as a disturbance that carries energy from one point to another without movement of particles
- Classify waves as mechanical (require a medium) or electromagnetic (do not require a medium) with examples
- Demonstrate the generation of waves using a slinky spring and a rope

- Discuss the meaning of waves using the conversation between Teacher Noel and Grade 9 learners about ocean waves at Malindi; define a wave as a disturbance that carries energy in an organised and regular way without movement of particles
- Classify waves: mechanical (water waves, sound waves — require a medium) and electromagnetic (radio waves, light waves — do not require a medium)
- Generate waves using a slinky spring: move free end up and down to produce transverse waves (humps and valleys); push free end horizontally to produce longitudinal waves (compressions and rarefactions) — Figures 3.46–3.49

What is a wave and what is the difference between mechanical and electromagnetic waves?

- Spotlight Integrated Science pg. 159
- Slinky spring, block board, metallic hooks, hammer
- Reference books

- Observation - Oral questions - Written assignments

Force and Energy

Waves - Meaning of waves and generation using a slinky spring

By the end of the lesson, the learner should be able to:

- Define a wave as a disturbance that carries energy from one point to another without movement of particles
- Classify waves as mechanical (require a medium) or electromagnetic (do not require a medium) with examples
- Demonstrate the generation of waves using a slinky spring and a rope

- Discuss the meaning of waves using the conversation between Teacher Noel and Grade 9 learners about ocean waves at Malindi; define a wave as a disturbance that carries energy in an organised and regular way without movement of particles
- Classify waves: mechanical (water waves, sound waves — require a medium) and electromagnetic (radio waves, light waves — do not require a medium)
- Generate waves using a slinky spring: move free end up and down to produce transverse waves (humps and valleys); push free end horizontally to produce longitudinal waves (compressions and rarefactions) — Figures 3.46–3.49

What is a wave and what is the difference between mechanical and electromagnetic waves?

- Spotlight Integrated Science pg. 159
- Slinky spring, block board, metallic hooks, hammer
- Reference books

- Observation - Oral questions - Written assignments

Force and Energy

Waves - Generation of waves using water, sound and phase

By the end of the lesson, the learner should be able to:

- Demonstrate generation of waves using water and a sound source
- Describe what happens when waves are in phase and out of phase
- Appreciate that waves are generated in various ways in nature and are all around us

In groups, learners are guided to:
- Generate water waves: drop small and large stones at the centre of a water-filled basin; observe circular ripples spreading outward (Figure 3.51); discuss how stone transfers energy to water particles
- Generate sound waves: connect a speaker to a signal generator through a plastic pipe covered with cling wrap and rice; observe rice jumping as the speaker creates longitudinal waves in air (Figures 3.52–3.54)
- Demonstrate phase: place two speakers 60 m apart connected to a signal generator; stand between them and move one speaker farther — observe increased sound (in phase) and no sound (out of phase) — Figures 3.55

How do water, sound and mechanical disturbances generate waves and what does it mean for two waves to be in phase?

- Spotlight Integrated Science pg. 162
- Basin, water, stones; speaker, signal generator, plastic pipe, cling wrap, uncooked rice, cellotape, retort stand
- Reference books

- Observation - Oral questions - Written assignments

Force and Energy

Waves - Classifying waves as longitudinal and transverse
Waves - Characteristics of waves: amplitude, frequency, period, wavelength, speed

By the end of the lesson, the learner should be able to:

- Distinguish between longitudinal waves (particle displacement parallel to wave motion) and transverse waves (particle displacement perpendicular to wave motion)
- Classify given waves as longitudinal or transverse with examples
- Draw diagrams showing particle displacement in longitudinal and transverse waves

- Define the characteristics of waves: amplitude, frequency, period, wavelength and speed
- State the units for each characteristic and apply the wave equation: speed = frequency × wavelength (v = fλ)
- Appreciate the importance of wave characteristics in describing the behaviour of waves

In groups, learners are guided to:
- Search digital media for animations on classification of waves; compare findings with classmates
- Study Betty's diagrams A and B (Figures 3.56–3.59) and identify which is longitudinal (slinky spring pushed back/forth — compressions and rarefactions) and which is transverse (rope moved up and down — humps and valleys); give reasons
- Classify waves from practical activities 1–3 as transverse or longitudinal; list other waves: longitudinal (sound, slinky pushed horizontally) and transverse (light, radio, microwaves, water waves); draw and label particle displacement diagrams for both types
- Use a ripple tank to demonstrate characteristics: produce straight waves with a wooden plank; reflect waves off a metal bar; observe circular waves through a gap — Figures 3.60–3.63
- Search reference materials to describe: amplitude (maximum displacement from rest position, in metres), frequency (number of complete waves per second, in Hz), period (time between two successive crests, T = 1/f), wavelength (distance between two successive crests or troughs, λ), speed (v = f × λ)
- Describe characteristics of longitudinal waves: wavelength is distance between two successive compressions or rarefactions; amplitude is distance between particles in compressed region — Figure 3.65

What is the difference between a longitudinal wave and a transverse wave and how can you identify each from a diagram?
How do the characteristics of a wave describe its behaviour and how are amplitude, frequency, wavelength and speed related?

- Spotlight Integrated Science pg. 165
- Digital media, slinky spring, rope, pole
- Reference books
- Charts (Figures 3.56–3.59)
- Spotlight Integrated Science pg. 167
- Ripple tank, wooden plank, metal bars, reference books
- Charts (Figures 3.64–3.65)

- Observation - Oral questions - Written assignments

Force and Energy

Waves - Characteristics of waves: amplitude, frequency, period, wavelength, speed

By the end of the lesson, the learner should be able to:

- Define the characteristics of waves: amplitude, frequency, period, wavelength and speed
- State the units for each characteristic and apply the wave equation: speed = frequency × wavelength (v = fλ)
- Appreciate the importance of wave characteristics in describing the behaviour of waves

In groups, learners are guided to:
- Use a ripple tank to demonstrate characteristics: produce straight waves with a wooden plank; reflect waves off a metal bar; observe circular waves through a gap — Figures 3.60–3.63
- Search reference materials to describe: amplitude (maximum displacement from rest position, in metres), frequency (number of complete waves per second, in Hz), period (time between two successive crests, T = 1/f), wavelength (distance between two successive crests or troughs, λ), speed (v = f × λ)
- Describe characteristics of longitudinal waves: wavelength is distance between two successive compressions or rarefactions; amplitude is distance between particles in compressed region — Figure 3.65

How do the characteristics of a wave describe its behaviour and how are amplitude, frequency, wavelength and speed related?

- Spotlight Integrated Science pg. 167
- Ripple tank, wooden plank, metal bars, reference books
- Charts (Figures 3.64–3.65)

- Observation - Oral questions - Written assignments

Force and Energy

Waves - Identifying parts of waves and wave calculations

By the end of the lesson, the learner should be able to:

- Identify and label parts of transverse and longitudinal waves from diagrams including crest, trough, compression, rarefaction, amplitude and wavelength
- Solve numerical problems using the wave equation v = fλ and the period formula T = 1/f
- Value precision in reading wave diagrams and performing wave calculations

In groups, learners are guided to:
- Use a rope and slinky spring: swing rope up and down and identify crest, trough, amplitude and wavelength in the transverse wave formed; push slinky horizontally and identify compression, rarefaction, amplitude and wavelength in the longitudinal wave — Figures 3.66 and 3.67
- Draw and label diagrams of a transverse wave (Figure 3.66) and a longitudinal wave (Figure 3.67) showing all parts
- Solve problems from the assessment activity: find frequency of a wave travelling at 64 m/s with wavelength 16 m; find frequency if three waves arrive in 5 seconds; share and discuss working with classmates

How can I use the wave equation and diagrams to calculate wave properties from given data?

- Spotlight Integrated Science pg. 170
- Rope, slinky spring, pole; pencil and ruler for diagrams
- Reference books

- Written assignments - Oral questions - Observation

Force and Energy

Waves - Meaning and process of remote sensing

By the end of the lesson, the learner should be able to:

- Define remote sensing as the process of monitoring physical characteristics of an area by measuring reflected and emitted radiation at a distance
- Describe the seven steps of the remote sensing process in correct sequence
- Show interest in how electromagnetic waves are used in remote sensing technology

In groups, learners are guided to:
- Use print or digital media to search for information on the relationship between remote sensing and waves; discuss findings with group members
- Study Mokeira's remote sensing diagram (Figure 3.68) and label parts A–G; arrange the seven process steps in the correct order: (i) energy source → (ii) radiation through atmosphere → (iii) interaction with target → (iv) sensor captures energy → (v) transmission and processing → (vi) analysis → (vii) application
- Discuss: visible light is an electromagnetic wave; remote sensing satellites use it to capture detailed images of Earth's surface

What is remote sensing and how do electromagnetic waves make it possible to study features of the Earth from a distance?

- Spotlight Integrated Science pg. 171
- Digital resources, reference books
- Charts of remote sensing process (Figure 3.68)

- Observation - Oral questions - Written assignments

Force and Energy

Waves - Applications of remote sensing

By the end of the lesson, the learner should be able to:

- State the applications of remote sensing: air safety, forest fire detection, forest mapping, weather assessment, animal census, car tracking, land boundary identification and road safety
- Match remote sensing applications to their descriptions using Column A and Column B activity
- Appreciate the wide range of benefits that remote sensing technology brings to society

In groups, learners are guided to:
- Match descriptions in Column A to applications in Column B (Table 3.3): detecting wildfires (fire fighting), land images (land boundaries), animal distribution (animal census), vehicle speed monitoring (road safety)
- Discuss additional applications: air safety (monitoring volcanic ash for aircraft), weather assessment (satellite imagery for meteorological departments), car tracking (GPS trackers for theft prevention), forest mapping (monitoring deforestation for afforestation planning)
- Discuss other uses of remote sensing; write short notes and share with classmates

How does remote sensing use waves to improve safety, conservation and land management in our society?

- Spotlight Integrated Science pg. 173
- Digital resources
- Reference books

- Oral questions - Written assignments - Observation

Force and Energy

Waves - Applications of transverse and longitudinal waves in daily life

By the end of the lesson, the learner should be able to:

- State the applications of transverse and longitudinal waves in day-to-day life including communication, medicine and navigation
- Identify areas in the school environment where wave knowledge has been applied
- Appreciate that waves are fundamental to most modern technologies

In groups, learners are guided to:
- Take a walk around the school environment and identify areas where wave knowledge has been applied (radio in office, mobile phone signal, light in classrooms, loudspeaker in assembly); record findings and share in class
- Study pictures A–D showing applications of waves; state the uses: sound waves (verbal communication, SONAR for locating submarines/fish), radio waves (radio and TV broadcasts), microwaves (mobile phone signals), light waves (vision and optical instruments)
- Discuss SONAR (sound navigation and ranging) and RADAR (radio detection and ranging using electromagnetic waves for air traffic control); write short notes

How do transverse and longitudinal waves make modern communication, navigation and medical technologies possible?

- Spotlight Integrated Science pg. 174
- Digital resources
- Reference books

- Oral questions - Written assignments - Observation

Force and Energy

Waves - Applications of transverse and longitudinal waves in daily life

By the end of the lesson, the learner should be able to:

- State the applications of transverse and longitudinal waves in day-to-day life including communication, medicine and navigation
- Identify areas in the school environment where wave knowledge has been applied
- Appreciate that waves are fundamental to most modern technologies

In groups, learners are guided to:
- Take a walk around the school environment and identify areas where wave knowledge has been applied (radio in office, mobile phone signal, light in classrooms, loudspeaker in assembly); record findings and share in class
- Study pictures A–D showing applications of waves; state the uses: sound waves (verbal communication, SONAR for locating submarines/fish), radio waves (radio and TV broadcasts), microwaves (mobile phone signals), light waves (vision and optical instruments)
- Discuss SONAR (sound navigation and ranging) and RADAR (radio detection and ranging using electromagnetic waves for air traffic control); write short notes

How do transverse and longitudinal waves make modern communication, navigation and medical technologies possible?

- Spotlight Integrated Science pg. 174
- Digital resources
- Reference books

- Oral questions - Written assignments - Observation

Force and Energy

Waves - Importance of waves in day-to-day life

By the end of the lesson, the learner should be able to:

- Explain the importance of waves to everyday life: hearing, vision, communication, weather forecasting, remote sensing and medical imaging
- Write a short paragraph appreciating the applications of transverse and longitudinal waves in daily life
- Show genuine appreciation for the role of waves in modern science and technology

In groups, learners are guided to:
- Read Musau's appreciation statement and discuss: sound waves enable group discussion and verbal communication; light waves enable vision at a distance
- Write a personal paragraph appreciating applications of waves in daily life based on Musau's example; read paragraphs to the class
- Organise a class debate on the motion "Remote sensing plays an important role in day-to-day life": prepare and debate points for and against; conclude whether you agree with the motion and give reasons

Why is an understanding of waves essential for appreciating and participating in the modern world?

- Spotlight Integrated Science pg. 178
- Digital resources
- Reference books

- Oral questions - Written assignments - Observation