UNIT 8: Light and its features

Nuria Sánchez ParraCEIP García Bellido

VOCABULARY• arrive… llegar• behave …comportarse• blurred …borroso• darken …oscurecer• emit …emitir• find…encontrar• glass…cristal• kilometers…kilómetros• let …dejar, permitir• light …luz• light rays ….rayos de luz• living things…seres vivos• material …cuerpo, material• matter …materia• mirror…espejo• move…moverse• opaque …opaco

• propagation…propagación• receive…recibir• reflect …reflejar• second…segundo• skin …piel• sources of light… fuentes luminosas• spread…propagarse• through …a tavés de • translucent …translúcido• transparent…tarnsparente• travel… viajar• straight …recto• with respect to… con respecto a • wood …madera•

Light

Light is a form of energy, the light energy.

Light energy can transform into other forms of energy, such as thermal energy or electric energy.

It can also produce changes in the living things. For example, it can darken our skin or help the plants to produce their food

Materials and light

Materials behave in two different ways with respect to the light:

o Materials that emit lighto Material that reflect light

• Materials that emit light. They are called sources of light. Depending on its origin sources of light can be:– Natural, such as the sun, other stars or fire.– Artificial, such as light bulbs.

• Materials that reflect light. They are the other materials, that don’t emit light. We see these materials because they reflect the light they receive.

• Video 1• Video 2• Video 3

Light propagation

When a light source emits light, it spreads; it moves until it finds other material.

Light propagation features are:• Light travels in all directions from the source

of light.• Light travels in straight lines.• Light travels very quickly, at 300,000

kilometers per second

Transparent, translucent and opaque materials.

When the light arrives to a material, this material behaves in a different way depending on the matter it is made up.

We can classify materials into three groups:o Transparent materialso Translucent materialso Opaque materials

• Transparent materials. Light can pass through them, such as glass.

• Translucent materials. Only part of the light can pass. Light rays separate into different directions. We see blurred objects through translucent materials.

• Opaque materials. Light doesn’t pass through them, such as wood or a mirror.

ACTIVITIES• Write two examples of:

– Transparent materials: …………………………………………….. and ……………………………………– Translucent materials: ……………………………………………… and ……………………………………– Opaque materials: …………………………………………….. and ………………………………………….

• Match:Opaque materials let light pass through.Transparent materials let light pass through but separate.Translucent materials don’t let light pass through. • Complete to summarize:

– …………………………………. is a ……………………………. of energy. Materials can ………………………………….. or …………………………………. the light. Materials that emit light are called……………………………………………………………………………….

– ………………………………travels in all …………………………………., in ……………………… …………………………………………… and at ……………………………………………………………………

• True or false? Rewrite the false sentences:

– Light passes through opaque materials.– Light passes through transparent materials.– A light bulb can emit light.– The sun is an artificial source of light.