🔬 Class 8 Science – Light: Mirrors and Lenses Original Visual Revision Notes
Aligned with the Class 8 Science syllabus. Independently created study material. Not affiliated with or endorsed by NCERT.
🌎 Real-World Analogy: Pick up a shiny spoon! Look at the hollow inside — you see yourself upside down. That is a concave mirror. Flip the spoon and look at the curved back — you see a tiny, wide view. That is a convex mirror. Now put a straw in a glass of water — the straw looks bent at the water's surface. That is refraction: light bends when it moves from water into air, just like when a lens bends light to focus it!
💡 Topic 1: What is Light?
Light helps us see things.
Light travels in straight lines.
It moves very fast.
We need light to see colours.
The Sun gives us natural light.
🧲 Topic 2: Reflection of Light
Light bounces off shiny surfaces.
This bouncing is called reflection.
A mirror reflects light well.
We see ourselves in a mirror.
Smooth surfaces reflect light better.
📏 Topic 3: Laws of Reflection
There are two laws of reflection.
Angle in equals angle out.
The angles are from the normal.
Normal is a line at 90 degrees.
Both rays stay in one plane.
🧬 Topic 4: Plane Mirror
A plane mirror is flat.
The image is the same size.
Left and right look swapped.
The image is behind the mirror.
We use it to see ourselves.
🔍 Topic 5: Concave Mirror
A concave mirror curves inward.
It can make images bigger.
Used in shaving mirrors.
Used in torches for light beams.
Dentists use it to see teeth.
🚗 Topic 6: Convex Mirror
A convex mirror curves outward.
It makes images look smaller.
It shows a wider view.
Used in vehicle rear-view mirrors.
Helps drivers see more area.
🌊 Topic 7: Refraction of Light
Light bends when it changes medium.
This bending is called refraction.
A straw looks bent in water.
Light slows down in glass.
Light speeds up in air.
🔎 Topic 8: Convex Lens
A convex lens is thick in middle.
It bends light inward.
Used in magnifying glass.
Used in cameras to focus.
Our eye has a convex lens.
👓 Topic 9: Concave Lens
A concave lens is thin in middle.
It spreads light outward.
Used in spectacles for short sight.
It makes images look smaller.
It helps people see far things.
🎯 Topic 10: Uses of Lenses
Spectacles fix our eyesight.
Cameras use lenses to take photos.
Microscopes help us see tiny things.
Telescopes help us see far things.
Lenses are very useful in daily life.
🎨 Section 2 — Easy Illustrations
Hover over elements to explore. Diagrams animate as you scroll.
Fig 1: Light bounces off a mirror. The angle in equals the angle out.
Fig 2: Plane is flat. Concave curves in. Convex curves out.
Fig 3: Light bends when it goes from air into water.
Fig 4: A convex lens brings light rays together at the focus point.
Fig 5: A concave lens spreads light rays outward.
✏️ Section 3 — Worked Examples
🔶 Example 1: Find the Reflected Angle
A light ray hits a mirror at 30 degrees. What is the reflected angle?
1The law says: angle in = angle out
2Angle in = 30 degrees
3So reflected angle = 30 degrees
✔ Answer: The reflected angle is 30 degrees.
🔶 Example 2: Which Mirror to Use?
A driver wants to see more road behind. Which mirror should be used?
1Plane mirror shows same size only.
2Concave mirror makes things bigger.
3Convex mirror shows a wider view.
✔ Answer: Use a convex mirror. It shows more area.
🔶 Example 3: Lens for Reading
A person cannot read small text. Which lens helps?
1Small text needs to look bigger.
2A convex lens makes things bigger.
3A magnifying glass is a convex lens.
✔ Answer: Use a convex lens (magnifying glass).
📋 Section 4 — Cheat Sheet
Word
Meaning
Light
Energy that helps us see
Reflection
Light bouncing off a surface
Normal
Line at 90 degrees to the mirror
Plane mirror
A flat mirror giving same size image
Concave mirror
Curves inward and makes images bigger
Convex mirror
Curves outward and shows a wider view
Refraction
Bending of light when it changes medium
Convex lens
Thick in middle and focuses light
Concave lens
Thin in middle and spreads light
Focus
Point where light rays meet
Magnifying glass
A convex lens that makes things look big
Spectacles
Glasses with lenses to fix eyesight
🏠 Section 5 — Take-Home Handout
Part A — Fill in the Blanks
1. Light bouncing off a surface is called __________.
2. A flat mirror is called a __________ mirror.
3. A concave mirror curves __________.
4. Bending of light is called __________.
5. A convex lens is thick in the __________.
Part B — True or False
1. Light travels in curved lines. ( )
2. Angle in equals angle out in reflection. ( )
3. A convex mirror makes images bigger. ( )
4. A magnifying glass uses a convex lens. ( )
5. Refraction happens when light changes medium. ( )
Part C — Short Answer
1. Name two uses of a concave mirror.
2. Why do we use convex mirrors in vehicles?
3. What does a convex lens do to light?
Part D — Match the Columns
Column A
Column B
1. Plane mirror
a. Makes images bigger
2. Concave mirror
b. Shows wider view
3. Convex mirror
c. Same size image
4. Convex lens
d. Spreads light
5. Concave lens
e. Focuses light
Part E — Draw and Label
Draw a ray of light hitting a mirror. Label the normal, angle in, and angle out.
✅ Detailed Solutions — Section 5 Practice
Part A — Fill in the Blanks (Answers)
1. Light bouncing off a surface is called reflection.
2. A flat mirror is called a plane mirror.
3. A concave mirror curves inward.
4. Bending of light is called refraction.
5. A convex lens is thick in the middle.
Part B — True or False (Answers)
1. False. Light travels in straight lines, not curved ones.
2. True. The angle of incidence always equals the angle of reflection.
3. False. A convex mirror makes images smaller but shows a wider view.
4. True. A magnifying glass has a convex lens that focuses light to make things look bigger.
5. True. Refraction happens when light moves from one medium (like water) into another (like air).
Part C — Short Answer (Answers)
1. Two uses of a concave mirror: doctor's head mirror (to focus light on patients) and solar cooker reflector (to focus sunlight for cooking).
2. Convex mirrors show a wider view in a small mirror — the driver can see more road and more vehicles behind, making it safer to reverse or change lanes.
3. A convex lens focuses light to a point. It bends parallel rays inward so they meet at the focal point. Used in magnifying glasses and cameras.
Part D — Match the Columns (Answers)
1 → c (Plane mirror gives a same-size image)
2 → a (Concave mirror makes images bigger)
3 → b (Convex mirror shows a wider view)
4 → e (Convex lens focuses light)
5 → d (Concave lens spreads light)
🃏 Section 6 — Revision Flashcards
What is reflection?
Light bouncing off a shiny surface.
What is the law of reflection?
Angle of incidence equals angle of reflection.
What does a concave mirror do?
It curves inward and can make images bigger.
Where do we use convex mirrors?
In vehicle rear-view mirrors to see more road.
What is refraction?
Bending of light when it enters a new medium.
What does a convex lens do?
It focuses light to a point. Used in magnifying glass.
What does a concave lens do?
It spreads light outward. Used in spectacles.
Name 3 uses of lenses.
Spectacles, cameras, and microscopes.
🧠 Section 7 — Mind Map
Mind Map: 8 key ideas of Light, Mirrors and Lenses.