Week 9 and Week 10 (Light, Heat, Thermal Expansion & Ohm's Law) PDF

Learning Package Term 1 – Weeks 9 & 10 Topics Covered: Characteristics & Properties of Light The Effects of Heat Linear Thermal Expansion Ohm’s Law Learning Objectives: Upon reading this learning package, you should be able to: describe t...

Learning Package Term 1 – Weeks 9 & 10 Topics Covered: Characteristics & Properties of Light The Effects of Heat Linear Thermal Expansion Ohm’s Law Learning Objectives: Upon reading this learning package, you should be able to: describe the different properties and characteristics of light; classify the radiation of the EM spectrum in terms of its arrangement; identify real-life examples of natural and artificial sources of light. describe the concept of heat and temperature; explain the effects of heat in terms of phase and temperature changes; identify real-life examples of absorption and removal of heat in a system. explain thermal expansion; solve problems involving linear thermal expansion; identify real-life examples of thermal expansion. explain the concept of Ohm’s law; solve problems involving Ohm’s Law; and identify real-life examples of Ohm’s Law. Lesson 1: Properties and Characteristics of Light Light is a form of electromagnetic radiation exhibiting wave-like and particle-like properties, a concept known as wave-particle duality (photons). It travels in the form of electromagnetic waves, which consist of oscillating electric and magnetic fields perpendicular to each other and the direction of propagation. These waves travel at a constant speed in a vacuum that is approximately 299,792,458 meters per second, commonly referred to as the speed of light. Light has a lot of characteristics. One of the most significant is its wavelength (λ), which is the distance between the peaks of the wave and is typically measured in nanometers (nm). The wavelength of light determines its color in the visible spectrum, ranging from approximately 400 nm (violet) to 700 nm (red) which is called the Visible Light Spectrum, visible only to our naked eye. Light can also exist beyond the visible spectrum, including ultraviolet (UV), infrared (IR), and even higher and lower frequencies like X-rays and radio waves. Properties of Light 1. Reflection occurs when light strikes a surface and bounces back into the original medium. The law of reflection states that the angle of incidence (the angle between the incoming light ray and the normal to the surface) is equal to the angle of reflection (the angle between the reflected ray and the normal). This principle governs how we see objects. Because light reflects off surfaces and into our eyes, enabling vision. Smooth surfaces, such as mirrors, reflect light in a highly organized manner (specular reflection), producing clear images, while rough surfaces scatter light in many directions (diffuse reflection), which is why most objects appear matte or non-shiny. The reflectivity of a material depends on its surface properties and the angle at which the light strikes it. 2. Refraction is the bending of light as it passes from one medium to another with a different optical density, such as from air into water or glass. This phenomenon occurs because the speed of light changes when it moves between materials with different refractive indices. The refractive index is a measure of how much light slows down in a medium relative to its speed in a vacuum. When light enters a denser medium (higher refractive index), it slows down and bends toward the normal; when it enters a less dense medium, it speeds up and bends away from the normal.  3. Diffraction refers to the spreading or bending of light waves when they encounter an obstacle or pass through a narrow aperture. This phenomenon is most noticeable when the size of the obstacle or aperture is comparable to the wavelength of the light. As light passes through a slit or around an object, it spreads out and interferes with itself, creating a pattern of bright and dark regions. 4. Polarization describes the orientation of the oscillating electric field in a light wave. Normally, light is unpolarized, meaning its electric field oscillates in all directions perpendicular to the direction of propagation. However, light can be polarized such that the electric field oscillates in a specific direction. Polarization can occur naturally, such as when sunlight reflects off water or glass surfaces, or it can be achieved artificially using polarizing filters. These filters block all light waves except those oscillating in a particular direction. Polarized light has numerous practical applications, including reducing glare in sunglasses, enhancing contrast in photography, and improving the clarity of LCD screens. Prism and Dispersion When light passes through a prism, a phenomenon known as dispersion occurs, where light is separated into its component colors (wavelengths). A prism is typically a transparent object with flat, polished surfaces, such as a triangular piece of glass. As light enters the prism, it is refracted, or bent, at different angles depending on its wavelength. Shorter wavelengths, like violet and blue, are refracted more than longer wavelengths, such as red and orange. This separation of light into its spectrum is because the refractive index of the material varies with the wavelength of light, a phenomenon called chromatic dispersion. This process creates a visible spectrum of colors, which is famously demonstrated in the dispersion of sunlight into a rainbow. Lesson 2: The Effects of Heat Important Terms Temperature is a measure of how hot or cold something is. It measures the average kinetic energy of these particles. The SI Unit for Temperature is Kelvin (K). Temperature is an important concept in science, and it's measured using different units depending on geographic location or scientific context. Celsius and Fahrenheit are used for everyday temperature measurements in different regions. While Kelvin and Rankine are absolute temperature scales used in scientific and engineering applications. Kinetic energy is the energy of motion, so the faster the particles are moving, the more kinetic energy they have, and the higher the temperature. Equilibrium refers to a state where all temperatures in the system are balanced, and no further changes occur unless something outside disturbs the system. Thermal equilibrium happens when two objects or substances in contact reach the same temperature. Once they are at the same temperature, there is no more net flow of heat between them. Thermal energy is the total amount of energy due to the motion and interactions of all the particles in the entire substance. The faster these particles move, the more kinetic energy they have, and the greater the substance's thermal energy. A joule (J) is named after James Prescott Joule. It is a unit of measurement used to quantify energy, work, or heat in the International System of Units (SI). In simple terms, a joule tells us how much energy is required to perform a certain task, like moving an object or heating something. What is Heat? Heat is defined as a form of energy that is transferred between systems or objects with different temperatures. It always flows from the hotter object to the cooler one until it reaches thermal equilibrium (same temperature). Heat is not the same as temperature; while temperature measures the average kinetic energy of particles in a substance, heat measures the energy transfer that occurs as a result of this temperature difference.  Thermal Equilibrium is the condition where two or more objects in contact with each other have reached the same temperature, resulting in no net heat transfer between them. The diagram illustrates the effects of heat on the phase changes of matter through a cyclical process involving solid, liquid, and gas states. It shows how heat energy affects the transitions between these states. Melting occurs when heat is added to a solid, turning it into a liquid. Freezing happens when a liquid loses heat and becomes solid. Evaporation (including boiling) occurs when heat is added to a liquid, converting it into a gas. Condensation happens when gas loses heat and turns back into a liquid. Sublimation, where a solid directly transitions to gas. While deposition is the reverse process where gas turns directly into a solid, highlighting the versatility of heat in facilitating phase changes. Sublimation - Dry Ice (Solid Carbon Dioxide) Dry ice is solid carbon dioxide (CO₂) that sublimates at temperatures above -78.5°C (- 109.3°F). When dry ice is exposed to room temperature, it does not melt into a liquid; instead, it directly changes from a solid to a gas, producing a visible fog. As the dry ice absorbs heat from the surrounding environment, the solid CO₂ particles gain enough energy to break free from their rigid structure, turning into carbon dioxide gas. This process can be observed during events such as Halloween or theatrical performances, where dry ice is used to create fog effects. Deposition - Frost Formation on Cold Surfaces Frost is a common example of deposition, occurring when water vapor in the air directly changes into ice crystals on surfaces that are below freezing (0°C or 32°F). In conditions where the air is humid and the temperature drops, water vapor loses energy and transitions directly from a gas to a solid state, forming frost on windows, grass, or other surfaces. This phenomenon is often seen on chilly mornings when dew freezes, creating a layer of frost. What Do You Have to Remember? Heat absorption and heat removal in a system as this doesn’t necessarily mean an increase or decrease in a system’s temperature but also a change in its phase. When a substance reaches its melting point, continued heat absorption does not increase the temperature further. Instead, the absorbed heat is used to break the intermolecular bonds holding the solid together, resulting in a phase change from solid to liquid (melting). The temperature remains constant during this process, despite the input of heat. Similar to heat absorption, heat removal can also lead to a phase change without a change in temperature. When the temperature of a liquid reaches its freezing point, continued heat removal will cause the liquid to solidify into a solid (freezing). During this process, the temperature of the liquid remains constant until all the liquid has transformed into a solid, even though heat is being removed. Air-Conditioned Systems Air conditioners absorb heat from the air inside a room and release it outside, cooling the indoor environment. Factors such as the insulation of the building, the temperature differential, and the maintenance of the system itself can affect the efficiency of air conditioning systems. Air conditioning systems are essential for maintaining comfortable indoor environments, especially in hot weather. They work based on the principles of heat transfer, particularly the processes of evaporation, condensation, and heat absorption/removal. Lesson 3: The Concept of Thermal Expansion Thermal expansion refers to the increase in size (length, area, or volume) of a material when it is heated. This happens because when substances are heated, their particles (atoms or molecules) gain kinetic energy and move more vigorously. All matter comprises tiny particles like atoms or molecules that are in constant motion. However, as the material is heated, the particles move faster, they tend to spread out from each other, causing the material to expand. Why meat products shrink after cooking. Does this contradict thermal expansion? No, when cooking fishballs or meats in general you may notice they expand in size while in hot oil but shrink after cooking. The shrinkage is due to the release of juices. Most materials expand when they are heated and contract when they are cooled, due to the increased kinetic energy of their particles at higher temperatures. These particles have energy, and the amount of energy they have depends on the temperature. Thermal expansion can happen in different ways depending on the state (solid, liquid, or gas) and the direction of expansion. These types are: Linear Expansion (1D expansion) Areal Expansion (2D expansion) Volumetric Expansion (3D expansion) Linear Thermal Expansion But the focus more is on Linear Thermal Expansion. Linear thermal expansion refers to the increase in length or size of a material when it is heated. When a solid object is heated, its atoms or molecules vibrate more vigorously, causing them to move slightly farther apart. This increase in the distance between particles leads to an expansion in the material's dimensions. For most materials, this expansion is relatively small but measurable, especially over large temperature ranges and it is expressed as: ΔL=αL0ΔT Initial Length (L₀): The initial length of the object before any temperature change. Temperature Change (ΔT): The difference between the initial and final temperatures. Coefficient of Linear Expansion (α): A material-specific constant that indicates how much the material expands per degree of temperature change. Each material has its own coefficient. Sample Problems What is the change in the length of an aluminum rod if its initial length is 1.22 m and the change in temperature is 30.0 °C? To solve for the change in length (Δ𝐿) of the aluminum rod due to thermal expansion, we can use the linear thermal expansion formula: α = 25×10−6 / °C (coefficient of linear expansion for aluminum), L0 = 1.22m (initial length) ΔT = 30.0°C (change in temperature). ΔL = ? 𝟐𝟓×𝟏𝟎−𝟔 ΔL = ( )(1.22 m)(30.0 °C) °𝐂 ΔL = 9.15 x 10-4 m At what change in temperature will a brass rod acquire a change in length of 18.9 x 10 -4 m if its initial length is 2.31? ΔL = 18.9 x 10-4 m α = 18.9 x 10-6 / °C (coefficient of linear expansion for aluminum), L0 = 2.31 m (initial length) ΔT = ? 𝟏𝟖.𝟗 𝐱 𝟏𝟎−𝟒 𝐦 ΔT = ( 𝟏𝟖.𝟗 𝐱 𝟏𝟎−𝟔 ) ( )(𝟐.𝟑𝟏 𝒎) °𝑪 ΔT = 43.29 °C Lesson 4: The Concept of Thermal Expansion  Light bulbs are typically used to provide illumination. Common applications include homes, streetlights, Automobiles, theaters, and stage Productions (Tanushevsk, 2016). Light bulbs have a variety of uses, especially if controlled lighting is needed for visibility, ambiance, or safety (Alman, 2018). How does a light bulb work? How do we control the brightness of a lamp? A light bulb works by converting electrical energy into light through a process known as incandescence. As the filament gets extremely hot, it starts to glow and emits visible light. This is the process of incandescence - where it now emits light due to heat. The brightness of a lamp can be controlled in several ways, depending on the type of light source and the method used to adjust the amount of electrical energy the lamp receives. By adjusting the electricity supplied to the lamp, less electricity flows through the light bulb, reducing the brightness. The Light Bulbs and other terms that was mentioned is one of the basic components of a Circuit. A circuit is a path that allows electricity to move from a power source to various devices (like a light bulb or motor) and then back to the power source to facilitate electric flow (Svoboda et al. 2019). Basic Components of a Circuit The battery serves as the voltage source in a circuit. The longer line is the positive terminal while the shorter one is the negative terminal.  The resistor is used to reduce the current flow in an electric circuit. Resistors do this by providing resistance, a property that opposes the movement of electrical charges (current) through the material. The switch closes and opens up the circuit. When the circuit is open (switch is closed), there wouldn’t be any current to flow. Vice versa, when the circuit is closed (switch is open), current will be able to flow. The wire serves as the pathway for the current to flow in the circuit. Without the wire, the circuit will not have its extension for the current to flow the its different components. The bulb turns the electricity (electric energy) to the light when the filament is heated. It is one of the common loads in a circuit, making it a crucial component in any lighting system. Ohm’s Law In a circuit, the voltage, current, and resistance work together to facilitate the electric flow, obeying the concept of Ohm's Law. Georg Simon Ohm, a German physicist and mathematician. He is best known for formulating Ohm's Law, which describes the relationship between voltage, current, and resistance in an electrical circuit. Ohm's Law states that the current flowing through a conductor or a circuit is directly proportional to the voltage and inversely proportional to the resistance of the electric circuit. If you increase the voltage (while keeping resistance constant), the current will increase. If you increase the resistance (while keeping voltage constant), the current will decrease. Sample Problems 1. What is the voltage of a circuit if the current passing through it is 1.50 A and the total resistance is 23Ω? V = 34.5 V 2. What is the total resistance in a circuit whose voltage is 15 V and the current flowing through it is 3.0 A? R = 5 Ω 3. What is the value of the current flowing in a circuit that has a resistance of 10 Ω and voltage of 40 V? I = 4 A Prepared by: Sir Lauro H. Esquillo Sir Marlon Louis R. Vizconde Science Teacher 8CDEF Science Teacher 8AB