⚡ Quick Revision: Quick Definitions & Core Terms
We see non-luminous objects only when light falls on them and reflects into our eyes.
Seeing = Light Source + Object + Eye
- Symbols: Source = gives light; Object = reflects light; Eye = receives light
- SI Unit: No numerical unit needed at this level
For Class 6 Light, most answers are definition-based. Focus on correct keywords: light, source, reflection and eye.
Luminous objects produce their own light vs non-luminous objects only reflect light.
S-O-E
Source gives light, Object reflects light, Eye receives light.
| Term | Quick Meaning | Example |
|---|---|---|
| Light | Helps us see | 🔥 Sunlight |
| Luminous | Gives own light | Sun, bulb, candle flame |
| Non-Luminous | Does not give own light | Moon, book, chair |
| Artificial Source | Human-made light source | Torch, lamp |
Do not write that the Moon is luminous. The Moon is non-luminous because it reflects sunlight.
Seeing = Light Reflected from Object to Eye
- Use: To explain how we see non-luminous objects.
- Unit: No numerical unit needed.
- Light is a form of energy that helps us see.
- Luminous objects produce their own light.
- Non-luminous objects do not produce their own light.
- The Moon is non-luminous.
- We see objects when reflected light enters our eyes.
⚡ Quick Revision: Rectilinear Propagation of Light
Light travels in a straight line. This is why shadows are formed behind opaque objects.
Light travels in straight lines
- Symbols: Light path is shown using a ray with arrow.
- SI Unit: No numerical unit needed at this level.
For ray diagrams, always draw light rays as straight lines with arrowheads showing direction.
Ray is one straight path of light vs beam is a group of rays.
L-S-S
Light travels in a Straight path and forms Shadows.
| Material Type | Light Passing | Example |
|---|---|---|
| Transparent | Allows most light | 🔥 Clear glass, air |
| Translucent | Allows some light | Butter paper, frosted glass |
| Opaque | Does not allow light | Wood, metal, book |
Do not draw curved light rays for basic ray diagrams. Light rays must be shown as straight lines.
Rectilinear Propagation = Straight Line Travel of Light
- Use: To explain shadows and ray diagrams.
- Unit: No numerical unit needed.
- Light travels in straight lines.
- A ray shows the path and direction of light.
- A beam is a group of light rays.
- Transparent materials allow most light to pass.
- Opaque materials block light and form shadows.
⚡ Quick Revision: Shadows and Eclipses
Three things are needed to form a shadow: light source, opaque object and screen.
Shadow = Light Source + Opaque Object + Screen
- Symbols: Source = gives light; Object = blocks light; Screen = receives shadow
- SI Unit: No numerical unit needed at this level
Eclipse = Shadow in Space
- Symbols: Sun, Earth and Moon must come in a straight line.
- SI Unit: No numerical unit needed.
For shadow questions, write the three conditions first: source, opaque object and screen.
Solar eclipse occurs when the Moon blocks sunlight from reaching Earth vs lunar eclipse occurs when Earth blocks sunlight from reaching the Moon.
S-O-S
Source, Opaque object, Screen are needed for a shadow.
| Concept | Meaning | Exam Point |
|---|---|---|
| Shadow | Dark patch | 🔥 Formed by blocking light |
| Umbra | Complete dark region | Central dark shadow |
| Penumbra | Partial dark region | Faint shadow |
| Eclipse | Shadow formed in space | Sun, Earth, Moon align |
A transparent object does not form a dark shadow like an opaque object because it allows light to pass through.
Shadow = Source + Opaque Object + Screen
- Use: To answer conditions for shadow formation.
- Unit: No numerical unit needed.
- Shadow is formed when an opaque object blocks light.
- Source, opaque object and screen are needed for shadow formation.
- Umbra is the completely dark part of a shadow.
- Penumbra is the partly dark part of a shadow.
- Eclipses occur due to shadows formed in space.
⚡ Quick Revision: Reflection of Light
A plane mirror forms an erect image of the same size as the object.
Reflection = Bouncing Back of Light
- Symbols: Incident ray = incoming ray; reflected ray = outgoing ray
- SI Unit: No numerical unit needed at this level
Image Size = Object Size
- Symbols: Image = picture formed in mirror; object = real thing in front of mirror
- SI Unit: Size may be measured in cm or m if numerical data is given
For plane mirror questions, remember: image is same size, erect and laterally inverted.
Regular reflection occurs on smooth surfaces vs irregular reflection occurs on rough surfaces.
S-E-L
Plane mirror image is Same size, Erect and Laterally inverted.
| Concept | Meaning | Example |
|---|---|---|
| Reflection | Bouncing back of light | 🔥 Mirror reflection |
| Regular Reflection | Clear reflection | Plane mirror |
| Irregular Reflection | Scattered reflection | Wall, paper |
| Lateral Inversion | Left-right reversal | Mirror image of text |
Do not write that a plane mirror image is upside down. It is erect.
Plane Mirror Image = Same Size + Erect + Laterally Inverted
- Use: To answer plane mirror image properties.
- Unit: No numerical unit needed unless size is measured.
- Reflection is the bouncing back of light.
- A plane mirror is a flat mirror.
- Smooth surfaces give regular reflection.
- Rough surfaces give irregular reflection.
- A plane mirror image is same size, erect and laterally inverted.
⚡ Quick Revision: Formulae, Units & Exam Readiness
There is no major numerical formula in Class 6 Light. Most questions test definitions, rules and diagrams.
Light → Straight Line Path
- Symbols: Arrow on ray shows direction of light.
- SI Unit: No numerical unit needed at this level.
Shadow = Source + Opaque Object + Screen
- Symbols: Source = light source; Object = blocks light; Screen = receives shadow.
- SI Unit: Shadow size may be measured in cm or m if asked.
Reflection = Bouncing Back of Light
- Symbols: Incident ray = incoming ray; reflected ray = outgoing ray.
- SI Unit: No numerical unit needed at this level.
In this chapter, diagrams matter more than calculations. Draw rays as straight lines and label source, object, screen, mirror and eye clearly.
Ray shows one path of light vs shadow is the dark region formed by blocking light.
S-S-R
Straight line, Shadow, Reflection are the three main scoring rules.
| Rule | Use in Exam | Unit Alert |
|---|---|---|
| Light travels straight | Ray diagrams | 🔥 No unit |
| Shadow needs S-O-S | Shadow conditions | cm or m only if size is measured |
| Reflection | Mirror questions | No unit |
| Plane mirror image | Image properties | Size unit only if measured |
Do not force a numerical formula where it is not required. In Light, clean definitions and labeled diagrams score more marks.
Light → Straight Line
Shadow = Source + Opaque Object + Screen
Reflection = Bouncing Back
- Use: Final rule-based revision.
- Unit: Mostly no unit; length units only if measurement is asked.
- Light travels in straight lines.
- Ray diagrams must have straight arrows.
- Shadow needs source, opaque object and screen.
- Reflection is bouncing back of light.
- Class 6 Light is mainly definition and diagram based.
⚡ Quick Revision: Final Recall Sheet & Exam Readiness
Light is a form of energy that helps us see objects, and it travels in straight lines.
Light → Straight Line Path
Shadow = Source + Opaque Object + Screen
Reflection = Bouncing Back of Light
- Symbols: Ray = path of light; Screen = surface for shadow
- SI Unit: No major numerical unit needed in this chapter
This chapter is mostly rule-based. Use correct keywords and draw clear labeled diagrams with straight rays.
| Topic | Must Remember | Example |
|---|---|---|
| Light | 🔥 Helps us see | Sunlight |
| Luminous | Gives own light | Sun, bulb |
| Rectilinear Propagation | Light travels straight | Ray diagram |
| Shadow | Formed by blocking light | Object shadow |
| Reflection | Bouncing back of light | Plane mirror |
Luminous object gives its own light vs non-luminous object reflects light from another source.
Do not write that the Moon is luminous. It is non-luminous because it reflects sunlight.
L-S-S-R
Light, Straight path, Shadow, Reflection.
Light → Straight Line Travel → Shadow Formation → Reflection → Plane Mirror Image
Seeing = Light Reflected from Object to Eye
Shadow = Source + Opaque Object + Screen
- Use: Definition, diagram and rule-based exam questions.
- Unit: No major numerical unit needed.
- Light is a form of energy that helps us see.
- Light travels in straight lines.
- Shadow needs source, opaque object and screen.
- Reflection is the bouncing back of light.
- A plane mirror image is same size, erect and laterally inverted.