Grade 8 Natural Sciences Visible light.pptx

Gr 8 Natural Sciences

1. Visible light

2. Light energy Light energy is emitted from luminous objects Reflects off some surfaces and objects Is absorbed by certain surfaces Is refracted by transparent objects

3. Luminous objects Luminous objects are light sources that radiate energy, for example, the sun, stars, candles, a glowing light bulb. Light is transferred by radiation.

4. Non-luminous objects Non-luminous objects are not a source of light energy. They reflect light of a luminous source e.g. the moon reflects light from the sun

5. Radiation of light The Sun is our main light source. Light travels from the sun through electromagnetic radiation . Light travels at a speed of 300 000 million kilometres per second . The sun is 150 million kilometres away from the earth. Light from the sun takes 30 seconds to reach the earth. Light travels in straight lines . It cannot bend around objects and that is why a shadow is formed.

6. Transparent, translucent and opaque objects Word bank Transparent: something that you can see through; light passes through the object Translucent: semi-transparent; some light is able to pass through but not enough for details to be seen clearly Opaque: something that you cannot see through; no light passes through the object

7. Classwork activity Transparent Translucent Opaque My example My example My example

8. The spectrum of visible light A triangular glass prism refracts (bends) white light into the colours of the spectrum. The colours of the spectrum are red , orange , yellow , green , blue , indigo and violet .