Education Always

Level: JHS, Basic 7  |  Subject: Integrated Science  |  Strand: Forces and Energy  |  Topic: Light

Curriculum reference: B7.4.1.3.1 (NaCCA Integrated Science).

1. What is Light?

• Light is a form of energy that lets us see.
• Luminous objects make their own light: the Sun, stars, a bulb, a candle flame.
• Non-luminous objects do not make light. We see them because they reflect light: the Moon, a book, a tree.
• Light travels very fast, about 300,000 km every second. It travels faster than sound, so we see lightning before we hear thunder.

2. Light Travels in Straight Lines

• Light travels in straight lines called rays. This is why we cannot see around a corner.
• Simple test: look through three cards, each with a hole in the centre. You can see a candle flame only when the holes are in a straight line.
• Shadows form because light cannot bend around an opaque object. A shadow is a dark area where light is blocked.

Type of material	What light does	Examples
Transparent	Passes through completely	Clear glass, clean water
Translucent	Passes partly	Frosted glass, oiled paper
Opaque	Does not pass through	Wood, metal, stone, cardboard

3. Reflection

• Reflection is the bouncing back of light when it hits a surface.
• Smooth, shiny surfaces such as a mirror give clear reflection.
• Law of reflection: the angle of incidence equals the angle of reflection.
• Image in a plane mirror: same size, upright, same distance behind the mirror, and laterally inverted (left and right are swapped).
• Uses: mirrors in homes, car side mirrors, periscopes, barbers’ mirrors.

4. Refraction

• Refraction is the bending of light when it passes from one transparent material to another, for example from air to water.
• A pencil in a glass of water looks bent. A coin in a bowl of water seems nearer the surface than it really is.
• Lenses (in spectacles, cameras and hand lenses) use refraction.

5. Dispersion

• Dispersion is the splitting of white light into its seven colours.
• The colours are red, orange, yellow, green, blue, indigo and violet (ROYGBIV).
• A glass prism splits white light into a spectrum. A rainbow forms when raindrops disperse sunlight.

Remember: Light travels in straight lines. Reflection is bouncing, refraction is bending, and dispersion is splitting into seven colours.

Education Always (education.inspiringalways.com). Original notes written to follow the NaCCA Basic 7 Integrated Science curriculum.