SCIENCE: LIGHT & SOUND.
CEIP Santa Ana Madridejos
LIGHT & SOUND. 1.- LIGHT.
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Light is a type of energy (radiation) that some bodies can emit and is visible to the human eye. Thanks to light, we can see shape, colour and size of every object. . This kind of energy can produce changes into living beings . (photosynthesis in plants, changes in the color of our skin) . and can be transformed into other kinds of energies like thermal or electric energy. Natural light source 1.1.- WHERE LIGHT IS PRODUCED. Every body that can produce light is called light source. There are natural sources like the Sun, stars, a lightnight… or artificial sources like bulbs, candles… . The rest of bodies reflect light. In a dark room we can’t see anything because objects don’t reflect light, but we can see them under a light… In the same way, we can see the moon because it reflects sunlight Artificial light source
1.2.- PROPAGATION OF LIGHT. Light propagates from one place to another. Light moves in this way: a .- Light moves straight: we can see straight rays of light in a foggy day, or from the headlights of a car. b.- Light moves in all directions: the light from a candle in a dark room moves in all directions to everywhere. c.- Light moves very fast ( 300.000 km per second, through vacuum). Light doesn’t need any support to move (air, water, solids…). Light from a lighthouse propagates straight and in all directions. 1.3.- MATERIALS AND LIGHT. When light gets to an object, this object responds depending on the material. We classify materials in three groups: A.- Transparent materials: they allow light to pass through the material, and we can see clear images through them (water, glass…). B.- Translucent materials: they allow light to pass through the material, but you can’t see clear through them (some kinds of plastic or glass). C.- Opaque materials: they don’t let the light to pass through the material, and you can’t see anything through them. They produce a shadow (a dark space behind an opaque object with light in front of it (wood, metals…) Transparent Translucent Opaque
SCIENCE: LIGHT & SOUND.
CEIP Santa Ana Madridejos
1.4.- PROPERTIES OF LIGHT. Light has two main properties: reflection and refraction. A) Reflection: is the change in direction of light when it collides with a body, and light returns (is reflected) and then we can see this body. Reflection permits us to see objects. A mirror is an opaque body with a polished surface that reflects light and images. Mirrors are: Reflection on the water. A.1.- Plane mirror: which has a flat surface, and doesn’t change shape and size from objects. A.2.- Curved mirrors: change shape and size from objects. 1.- Concave mirrors: provide bigger images (special mirrors in toilets). 2.- Convex mirrors provide a wider field of view, and smaller images (used in vehicles, road junctions…)
Concave mirror
Convex mirror
B) Refraction is the change of direction of light when it changes from one transmission medium to another (from air to water…).If we put a pencil into a glass of water, it looks like it is bent. This is because light speed in air is different than light speed in water. Refraction is used to make lens. A lens is a transparent piece of glass or plastic with one or two curved sides. Light is refracted inside, and changes its direction, and images are modified (We can see them bigger and more clear).
Refraction in a glass of water
There are two types: B.1.- Convex Lens: like magnifying glass that makes things appear bigger. B.2.- Concave Lens: makes things appear smaller. Convex & concave lens
1.5.- COLOUR. White light from the Sun can be separated in the seven colours from the rainbow: red, orange, yellow, green, blue, indigo and violet. This is called dispersion of light. When it rains, and sunrays go through drops of water, white light disperses and forms the rainbow in the sky.
SCIENCE: LIGHT & SOUND.
CEIP Santa Ana Madridejos
If light is white, why do we see objects in different colours?. . Because when objects receive white light, they absorb different colours and reflect the rest of them For example, if we see an object in red, is because it absorbs all colours and it reflects red. Snow reflects all colours, so we can see it in white. On the contrary, coal absorbs all colours and doesn’t reflects any of them, so we see coal in black. Reflection of white light in different objects
2.- THE SOUND. Sound is a form of energy produced by objects when they vibrate. These vibrations can produce some changes in objects: the vibrations from the explosion of a bomb can break window glasses. The sound can be produced in many ways: from a hit, a scratch, a blow… These actions make objects víbrate, so they produce different sounds. 2.1.- CHARACTERISTICS OF SOUND. When an object vibrates, produces a special sound. This sound is transmitted by waves. These waves have a frequency. Human ear can identify sounds because of its characteristics: 1.- Sound intensity: is the quantity of sound: the volume. There are loud sounds and low sounds (scream / whisper). 2.- Tone: there are high sounds (high frequency: lots of vibrations per second) and bass or low sounds (low frequency: few vibrations per second). Children have a high voice and men have low voices. 3.- Quality: makes it possible to distinguish one source of sound from another one. We can identify one person or one musical instrument by its quality. 2.2.- HOW SOUND PROPAGATES. Sound waves propagate from one place to another through a transmission means (solid, liquid or gas). Sound can’t propagate in vacuum. Sound propagation is: 1.- Sound moves straight 2.- Sound moves in all directions. 3.- Sound is slower than light: 340 m per second. Echo is the reflection of sound, arriving to the listener some time after the direct sound (walls from an empty room reflect sound and make echo). 2.3.- NOISE. Noise is an unpleasant and irritating sound. Noises too intense and loud like dense traffic, planes, trains, high volume music… is bad for people’s health. Noise pollution may cause nervous problems, stress, loss of hearing... It’s a very important problem in our society.
SCIENCE: LIGHT & SOUND.
CEIP Santa Ana Madridejos
GLOSARY-VOCABULARY. Shape: forma size: tamaño kind: clase change: cambio skin: piel thermal: térmica lightnight: relámpago bulb: bombilla light source: fuente luminosa candle: vela to reflect: reflejar the rest of…: el resto de… anything: algo, nada the moon: la luna in the same way: del mismo modo propagation: propagación straight: recto all directions: todas direcciones everywhere: todos los lados. fast: rápido through vacuum: a través del vacío support: soporte, medio material lighthouse: faro materials: materiales to get: llegar classify: clasificar clear: claro they allow light to pass: permiten a la luz pasar glass: cristal translucent: translúcido opaque: opaco shadow: sombra reflection: reflexión refraction: refracción to collide: chocar to return: volver mirror: espejo polished surface: superficie pulida plane mirror: espejo plano flat: plano to provide: producir convex: convexo wider field of view: campo de vision más amplio road junctions: cruces de calles transmission medium: medio de transmission light speed: velocidad de la luz it looks like it is bent: parece que está torcido curved side: cara curva magnifying glass: lupa to appear: parecer rainbow: arco iris indigo: añil, azul oscuro sunray: rayo de sol drop of water: gota de agua to disperse: separarse to absorb: absorber, quedarse con on the contrary: por el contrario coal: carbon sound: sonido to vibrate: vibrar bomb: bomba to break: romper hit: golpe to scratch: rozar, rascar to blow: soplar wave: onda frequency: frecuencia human ear: oído humano to identify: identificar intensity: intensidad loud sound: volume alto (fuerte) low sound: sonido débil high sound: agudo bass, low sound: sonido bajo (grave) quality: cualidad, timbre source of sound: fuente de sonido transmission means: medio de transmission slower than…: más lento que… echo: eco listener: el que escucha empty room: habitación vacía unpleasant, irritating: desagradable dense traffic: tráfico denso plane: aviones people’s health: salud de las personas loss of hearing: pérdida de audición nervous problems: problemas nerviosos noise pollution: contaminación acústica