Light

Summary

Light is a form of energy that can travel through empty space and is emitted by luminous sources. It allows us to see objects when it is reflected, transmitted, or absorbed by them.

• Light — a way of transferring energy that can travel through empty space.
  Example: Light from the Sun reaches Earth through space.
• Luminous — objects that emit their own light.
  Example: The Sun and stars are luminous objects.
• Shadow — a dark area where light is blocked by an opaque object.
  Example: On a sunny day, your body creates a shadow on the ground.
• Opaque — materials that do not let light pass through.
  Example: Bricks are opaque.
• Transparent — materials that let light pass through clearly.
  Example: Clear glass is transparent.
• Translucent — materials that let light through but scatter it.
  Example: Frosted glass is translucent.
• Emit — when an object gives out light.
  Example: A light bulb emits light.
• Transmit — when light passes through an object.
  Example: Light is transmitted through transparent glass.
• Reflect — when light bounces off an object.
  Example: Light reflects off a mirror.
• Absorb — when light is taken in by an object, often causing it to heat up.
  Example: Dark clothing absorbs more light and feels warmer in the sun.

Exam Tips

Key Definitions to Remember

• Light: a way of transferring energy that can travel through empty space
• Luminous: objects that emit their own light
• Shadow: a dark area where light is blocked by an opaque object
• Opaque: materials that do not let light pass through
• Transparent: materials that let light pass through clearly
• Translucent: materials that let light through but scatter it
• Emit: when an object gives out light
• Transmit: when light passes through an object
• Reflect: when light bounces off an object
• Absorb: when light is taken in by an object

Common Confusions

• Confusing 'emit' with 'transmit'
• Thinking shadows can form without a light source

Typical Exam Questions

• Name two luminous objects other than the Sun?
  Light bulb, candle
• What can a shadow tell you about the size of the source of light?
  A small light source creates a sharp shadow, while a large one creates a blurred shadow.
• Explain the difference between the words ‘emit’ and ‘transmit’?
  Emit means to give out light, while transmit means to allow light to pass through.

What Examiners Usually Test

• Understanding of how light travels and interacts with different materials
• Ability to explain the formation and characteristics of shadows
• Knowledge of how the human eye perceives light