Light, Shadows and Reflection: Class 6 Study Guide
We see things when light from them reaches our eyes. Light travels in straight lines.
Objects that give out their own light, such as the Sun and a lamp, are luminous. We see other objects because they reflect light into our eyes. Light travels in straight lines, which is why we cannot see around a corner.
Materials differ in how they let light pass: transparent materials (clear glass) let almost all light through, translucent ones (tracing paper) let some through, and opaque ones (wood, metal) let none through.
Shadows
A shadow forms when an opaque object blocks light. We need a source of light, an opaque object and a screen. A shadow is smaller when the object is closer to the screen and larger when it is closer to the source. The shadow of an object is dark because light cannot bend around it.
| Material | Type | Does it make a shadow? |
|---|---|---|
| Clear glass | Transparent | Almost none |
| Tracing paper | Translucent | A faint shadow |
| Cardboard | Opaque | A dark shadow |
Pinhole camera
A pinhole camera is a box with a tiny hole in one side and a screen of tracing paper on the other. It forms an upside-down image of a bright scene, because light from the top of the object goes through the hole to the bottom of the screen, and light from the bottom goes to the top.
In one end of a box.
A screen.
Look at the screen.
Upside down.
Mirrors
A mirror has a smooth, shiny surface and reflects light in a regular way. The image in a plane mirror is as far behind the mirror as the object is in front, the same size and left–right reversed. Light reflected from rough surfaces scatters, so we do not see a clear image.
Worked examples and common mistakes
Example: Is tracing paper opaque? No, it is translucent. Example: Why is a pinhole image inverted? Light travels in straight lines. Common mistakes: thinking that the Moon is luminous (it reflects sunlight), and thinking that a shadow is a reflection. A shadow is the absence of light.
Check your understanding: model answers
1. No, it only reflects sunlight. 2. For example tracing paper or frosted glass. 3. An opaque object blocks the light, and light does not bend around it.
✨ Key Takeaways
- Light travels in straight lines.
- Transparent, translucent and opaque materials differ in how much light they let through.
- A shadow needs a source, an opaque object and a screen.
- A pinhole camera forms an inverted image.
💬 Questions for Discussion & Reflection
- Is the Moon luminous?
- Name one translucent material.
- Why is a shadow dark?
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