01Light travels in straight lines
Light travels in straight lines called rays, at extremely high speed (about 300,000 km per second in a vacuum). This is why objects cast sharp shadows.
02Reflection
Reflection happens when light bounces off a surface. On a smooth surface (like a mirror), reflection is regular and produces a clear image. On a rough surface, light scatters in many directions (diffuse reflection).
03Refraction
Refraction is the bending of light as it passes from one transparent material into another (e.g. air into water), because light changes speed in different materials.
This is why a straw appears bent at the water's surface.
04Colour
White light (like sunlight) is actually a mixture of all colours. An object's colour is the colour of light it reflects — it absorbs all other colours.
A red apple looks red because it reflects red light and absorbs the rest of the visible spectrum.
05The electromagnetic spectrum
Visible light is only a small part of the electromagnetic spectrum, which also includes radio waves, microwaves, infrared, ultraviolet, X-rays and gamma rays — all travelling at the same speed but with different wavelengths and frequencies.
| Term | 한국어 | Meaning |
|---|---|---|
| ray | 광선 | A straight line showing the path of light |
| reflection | 반사 | Light bouncing off a surface |
| refraction | 굴절 | Light bending as it changes material |
| transparent | 투명한 | Allows light to pass through clearly |
| spectrum | 스펙트럼 | The full range of colours/wavelengths of light |
| absorb | 흡수하다 | To take in light energy rather than reflect it |