5º NATURALES - ESQUEMA TEMA 5

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Light: form of energy that let us see objects

Natural Sources                               

The sun                                            

A lightning    

                               

Artificial Sources

lightbulbs

 candles 

To make light we need a chemical reaction: a candle, bateries…

Characteristics of light

1) Speed: 300.000 km/s

2) Colour: seven colours

3) Direction: all directions

Materials and light

Transparent           √         light                             √      see

Translucent            √         light                             X      see

Opaque                 X         light                             X      see

Reflection

Rough (rugosa) surface: many directions

Smooth (lisa) surface: one direction

Refraction: when light changes direction: binoculars, glasses, a magnifying glass (lupa)

Mirrors are reflectors

Glasses are refractors

HEAT

Thermal energy from hotter to colder object

                Thermal conductors transmit heat. Metals

                Thermal insulators avoid heat. Plastic

Effects

1.       Melting: liquids

2.       Evaporation: gas

3.       Expansion: the volume increases