Chapter 15: Light, Shadows, and Reflection 💡
A Comprehensive Guide for PSTET Paper-2 (Science)
Chapter Overview
| Section | Topic | PSTET Weightage | Page No. |
|:---:|:---|::---:|:---:|
| 15.1 | Sources of Light (Luminous and Non-luminous) | Medium | 2 |
| 15.2 | Formation of Shadows (Opaque, Translucent, Transparent Objects) | High | 7 |
| 15.3 | Pinhole Camera | Medium | 13 |
| 15.4 | Reflection of Light (Plane Mirror - Regular and Diffused) | High | 18 |
| Practice Zone | MCQs & Pedagogical Questions | - | 25 |
Learning Objectives 🎯
After studying this chapter, you will be able to:
✅ Classify objects as luminous or non-luminous based on their ability to produce light
✅ Differentiate between natural and artificial sources of light with examples
✅ Explain shadow formation based on the properties of transparent, translucent, and opaque materials
✅ Describe the working principle of a pinhole camera and the characteristics of the image formed
✅ State the laws of reflection and distinguish between regular and diffused reflection
✅ Explain the characteristics of images formed by a plane mirror
✅ Apply pedagogical strategies to teach light-related concepts effectively to upper primary students
Pedagogical Link 🔗
For Teachers: This chapter directly aligns with:
Class 6 Science NCERT Chapter 11: "Light, Shadows and Reflections"
Class 7 Science NCERT Chapter 15: "Light"
Class 8 Science NCERT Chapter 16: "Light"
Teaching Tips:
Begin with a "Light Hunt" activity—students identify light sources in the classroom
Use hands-on investigations with torches and various materials to explore shadow formation
Have students make their own pinhole cameras using simple materials (cardboard box, tracing paper)
Use mirrors and laser pointers (with safety precautions) to demonstrate reflection
Create shadow puppet shows to make learning fun and memorable
Section 15.1: Sources of Light (Luminous and Non-luminous) 🔦
Introduction
Have you ever wondered why we can see objects around us? We see things because light from them enters our eyes. But where does this light come from? Some objects create their own light, while others merely reflect light from elsewhere. Understanding this difference is the foundation of studying light .
15.1.1 What is Light?
Definition: Light is a form of energy that enables us to see things around us . It travels in straight lines and behaves both as a wave and as a particle.
Key Properties of Light:
Light travels in straight lines (rectilinear propagation)
It travels at an enormous speed: 3 × 10⁸ m/s in vacuum
Light can be reflected, refracted, and absorbed
It requires no medium to travel (can travel through vacuum)
15.1.2 Luminous Objects
Definition: Luminous objects are objects that have their own source of light energy . They generate and emit light on their own. You are able to see luminous objects even in complete darkness .
Examples of Luminous Objects:
Sun (our primary natural light source)
Stars (including our Sun)
Fire (flames)
Electric bulbs (when switched on)
Torchlight
Lightning during a storm
Fireflies (bioluminescent insects)
Glow sticks (chemiluminescence)
Candle flame
📝 PSTET Note: A burning coal is luminous, but the same coal when not burning is non-luminous .
15.1.3 Non-luminous Objects
Definition: Non-luminous objects are objects that do not have their own source of light energy . They become visible only when light from a luminous source falls on them and reflects into our eyes . You cannot see non-luminous objects in the dark .
Examples of Non-luminous Objects:
Moon (reflects sunlight)
Planets (reflect sunlight)
Furniture (chair, table, desk)
Books and pen
Clothes
Your own body
Most objects around us
🌍 Did You Know? The moon is often called a "light source" in poems and songs, but scientifically it is non-luminous. We see the moon only because it reflects light from the sun .
How We See Non-luminous Objects:
Light source (Sun/bulb) → Falls on non-luminous object → Reflects off object → Enters our eyes → Brain interprets as vision
15.1.4 Classification Based on Origin: Natural vs. Artificial
Light sources can also be classified based on whether they occur naturally or are man-made .
Table 15.1: Natural vs. Artificial Light Sources
| Category | Definition | Examples |
|---|---|---|
| Natural Light Sources | Light sources that occur in nature without human intervention | Sun, stars, lightning, fire (natural fires), fireflies, glowworms, bioluminescent sea creatures |
| Artificial Light Sources | Light sources created by humans | Electric bulbs, tube lights, CFLs, LEDs, candles, oil lamps, torches, lasers, mobile phone screens |
15.1.5 Types of Artificial Light Sources
Artificial light sources can be further divided into three categories based on how they produce light :
A. Incandescent Light Sources
How They Work: Certain objects emit light when heated to a high temperature .
Examples:
Electric bulbs (filament converts electrical energy to heat, then to light)
Candles (flame heats wax particles)
Firewood (burning produces light)
B. Luminescent Light Sources
How They Work: These sources emit light without producing significant heat (non-incandescent).
| Type of Luminescence | How It Works | Examples |
|---|---|---|
| Chemiluminescence | Light emission due to chemical reaction | Glow sticks, some science experiments |
| Bioluminescence | Chemical reaction in living organisms converting chemical energy to light | Fireflies, glowworms, bioluminescent plankton and clams |
| Electroluminescence | Light emitted when electric field interacts with a solid | Car dashboard displays, LED headlights |
| Fluorescence | Material absorbs energy and immediately emits light | Fluorescent tube lights, highlighter pens |
| Phosphorescence | Material absorbs energy and slowly emits light over time | Glow-in-the-dark toys, safety signs |
Key Difference: Fluorescence stops emitting light as soon as the energy source is removed; phosphorescence continues to glow for some time after .
C. Gas Discharge Light Sources
How They Work: Electricity passes through a gas, causing it to emit light .
Examples:
Fluorescent tubes
Neon signs
Street lights (sodium vapor lamps)
15.1.6 Primary vs. Secondary Light Sources
Another useful way to classify light sources :
| Type | Definition | Examples |
|---|---|---|
| Primary Sources | Objects that generate their own light (luminous) | Sun, bulb, flame, firefly |
| Secondary Sources | Objects that do not generate light but reflect light from primary sources (non-luminous) | Moon, table, chair, book |
📝 PSTET Note: A simple way to remember: Primary sources = luminous; Secondary sources = non-luminous .
15.1.7 Can Non-luminous Objects Become Luminous?
Yes! Some non-luminous objects can be made luminous through various phenomena :
| Phenomenon | Process | Example |
|---|---|---|
| Blackbody radiation | Heating an object to very high temperature causes it to glow | An iron rod placed in fire becomes red-hot and emits light |
| Chemical reaction | Certain chemicals react to produce light | Some non-luminous materials can be made to glow through chemiluminescence |
15.1.8 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Sorting Activity | Students sort pictures/objects into luminous and non-luminous categories | Classification skills |
| "Why Can We See?" Discussion | Discuss why we can see objects in a room when the light is on, but not when it's off | Conceptual understanding |
| Moon Observation | Observe moon phases and discuss why we see different amounts each night | Real-world connection |
| Light Hunt | Students find and list all light sources in their home/school | Observation skills |
Section 15.2: Formation of Shadows (Opaque, Translucent, Transparent Objects) 🌑
Introduction
Have you ever played with your shadow on a sunny day? Or noticed how your shadow changes length from morning to noon to evening? Shadows are fascinating phenomena that teach us important lessons about how light behaves .
15.2.1 Why Do Shadows Form?
Basic Principle: Light travels in straight lines. When an object blocks the path of light, a dark area is formed on the opposite side of the object . This dark area is called a shadow.
Conditions for Shadow Formation:
There must be a source of light
There must be an opaque or translucent object to block the light
There must be a surface (screen, ground, wall) where the shadow falls
The Three Elements Must Be in Line:
Light Source -----> Object -----> Shadow (Light travels in straight line)
15.2.2 Types of Objects Based on Light Transmission
Materials can be classified into three categories based on how they interact with light :
Table 15.2: Transparent, Translucent, and Opaque Materials
| Category | Definition | Light Transmission | Can You See Through? | Shadow Cast | Examples |
|---|---|---|---|---|---|
| Transparent 🔍 | Materials that allow most light to pass through them in straight lines | Almost all light passes through | Clearly | No shadow or very faint shadow | Clear glass, clean water, air, cellophane, cling wrap |
| Translucent 🌫️ | Materials that allow some light to pass through, but scatter the light | Some light passes through; light is scattered | Not clearly; objects appear blurry | Faint, soft-edged shadow | Frosted glass, butter paper, tissue paper, thin cloth, oily paper |
| Opaque 🚫 | Materials that do not allow any light to pass through | No light passes through | Not at all | Dark, sharp shadow | Wood, metal, stone, cardboard, thick plastic, book, human body |
📝 PSTET Note: For a shadow to be formed, light must be obstructed. Since transparent objects allow light to pass through them completely, they cannot cast a shadow . Translucent objects cast faint shadows; opaque objects cast dark shadows.
15.2.3 Shadow Formation Explained
Step-by-Step Process:
| Step | What Happens |
|---|---|
| 1 | Light from a source travels in straight lines in all directions |
| 2 | An opaque object is placed in the path of light |
| 3 | The object blocks the light rays that hit it |
| 4 | Light rays that are not blocked continue straight |
| 5 | The region behind the object that receives no light appears dark—this is the shadow |
| 6 | The shadow always forms on the opposite side of the object from the light source |
Ray Diagram:
Light Source
☀️
|
| (Light rays)
|
-----|----- Object (opaque)
| 🧱
| |
| |
| Shadow
| 🌑
(Screen/ground)15.2.4 Characteristics of Shadows
| Characteristic | Description |
|---|---|
| Shape | Shadow roughly resembles the shape of the object, but is a silhouette (no details) |
| Colour | Shadows are always dark/black regardless of the object's colour |
| Position | Always on the opposite side of the object from the light source |
| Size | Depends on distance between light source and object, and object and screen |
| Sharpness | Depends on the type of object (opaque = sharp; translucent = fuzzy) and light source size |
15.2.5 Factors Affecting Shadow Size and Shape
A. Distance from Light Source
| Object Position | Shadow Size | Explanation |
|---|---|---|
| Closer to light source | Larger shadow | Object blocks more light rays |
| Farther from light source | Smaller shadow | Object blocks fewer light rays |
B. Distance from Screen
| Screen Position | Shadow Size | Explanation |
|---|---|---|
| Closer to object | Sharper, smaller shadow | Less space for light to spread |
| Farther from object | Larger, fuzzier shadow | Light rays have more space to spread |
C. Angle of Light Source
| Time of Day | Sun's Position | Shadow Length |
|---|---|---|
| Morning/Evening | Low angle | Long shadows |
| Noon | High overhead | Very short shadows (almost under object) |
15.2.6 Umbra and Penumbra
When the light source is not a point but has size (like the Sun or a large bulb), shadows have two distinct regions :
| Region | Definition | Description | Light Condition |
|---|---|---|---|
| Umbra 🌑 | The inner, darker part of a shadow | Where the light source is completely blocked by the object | No light reaches |
| Penumbra 🌓 | The outer, lighter part of a shadow | Where the light source is only partially blocked | Some light reaches |
Real-life Example: During a solar eclipse, people in the umbra region see a total eclipse, while those in the penumbra see a partial eclipse.
15.2.7 Shadows and Transparent/Translucent Objects
15.2.8 Common Misconceptions About Shadows
| Misconception | Scientific Fact |
|---|---|
| Shadows are "things" that exist independently | Shadows are merely absence of light; they have no existence without object and light |
| Shadows are copies of the object | Shadows are silhouettes without details; they don't show colors or features |
| Shadows are always attached to objects | Shadows are separate from objects and can be on different surfaces |
| Shadows can be coloured like the object | Shadows are always dark, regardless of object's colour |
15.2.9 Fun with Shadows: Shadow Puppets
Shadow puppetry is an ancient art form that uses the principles of shadow formation. By positioning hands or cutouts between a light source and a screen, beautiful shadow images can be created.
Classroom Activity: Shadow Puppet Show
| Step | Procedure |
|---|---|
| 1 | Set up a light source (torch or lamp) facing a white wall or screen |
| 2 | Students create shadow puppets using their hands (bird, dog, rabbit, etc.) |
| 3 | Experiment with distance to change shadow size |
| 4 | Students can create stories and perform for the class |
15.2.10 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Material Testing Station | Students test various materials with torch to classify as transparent, translucent, opaque | Hands-on investigation |
| Shadow Tracing | Students trace each other's shadows at different times of day | Observation and measurement |
| "Why No Shadow?" Question | Challenge students to find objects that don't cast shadows (transparent ones) | Critical thinking |
| Shadow Puppet Show | Creative activity applying shadow concepts | Engaging multiple intelligences |
Section 15.3: Pinhole Camera 📷
Introduction
A pinhole camera is one of the simplest optical devices ever invented. Despite its simplicity, it demonstrates fundamental principles of light—that light travels in straight lines and forms images. Understanding how a pinhole camera works helps us understand more complex cameras and even how our eyes work .
15.3.1 What is a Pinhole Camera?
Definition: A pinhole camera is a simple camera without a lens, consisting of a light-proof box with a tiny hole (pinhole) on one side and a translucent screen (or photographic film) on the opposite side .
Principle: It works on the principle that light travels in straight lines (rectilinear propagation of light) .
15.3.2 Construction of a Pinhole Camera
Materials Required:
A cardboard box (or cylindrical container like a tin can or cardboard tube)
Black paint (to make inside light-proof)
Thick black paper or aluminum foil
A needle or pin (to make the tiny hole)
Tracing paper or butter paper (for the screen)
Procedure:
| Step | Action |
|---|---|
| 1 | Take a cardboard box and paint the inside black (prevents unwanted reflections) |
| 2 | Cut a small square hole (about 2 cm × 2 cm) in the center of one side |
| 3 | Cover this hole with thick black paper or aluminum foil |
| 4 | Make a tiny, clean hole in the center of the foil using a pin (this is the aperture) |
| 5 | On the opposite side, cut a larger square window and cover it with tracing paper (this is the screen) |
| 6 | Ensure no light enters except through the pinhole |
15.3.3 How a Pinhole Camera Works
Working Principle:
Ray Diagram:
Object Screen
↑ ↓
| |
-----|----- |
| | Pinhole |
| A | • | Image (inverted)
| | -----/---- | ↓
| B |---/----------\------|---- ↑
| | / \ |
|__________| / \____|
Light rays cross at pinholeWhy the Image is Inverted:
The pinhole acts as a point through which all light rays must pass. Because light travels in straight lines, rays from the top of the object must travel downward to reach the bottom of the screen, and rays from the bottom travel upward. This crossing effect causes the image to appear upside down .
15.3.4 Characteristics of Image Formed by Pinhole Camera
| Characteristic | Description |
|---|---|
| Nature | Real image (can be projected on screen) |
| Orientation | Inverted (upside down) |
| Lateral inversion | Left-right reversed |
| Colour | Same colour as object |
| Sharpness | Depends on size of pinhole |
| Brightness | Depends on size of pinhole and ambient light |
15.3.5 Factors Affecting the Image
A. Size of the Pinhole
B. Distance Between Pinhole and Screen (Focal Length)
| Distance | Effect on Image |
|---|---|
| Shorter distance | Smaller image |
| Longer distance | Larger image |
This relationship is given by:
Image size = (Object size × Distance to screen) / Distance to object
C. Distance Between Object and Pinhole
| Object Distance | Effect on Image |
|---|---|
| Closer | Larger image |
| Farther | Smaller image |
15.3.6 Advantages and Limitations of Pinhole Camera
Advantages:
Simple construction with easily available materials
No lens required (no focusing issues)
Infinite depth of field (everything in focus from near to far)
No distortion (common in lens cameras)
Limitations:
Very dim image (especially in low light)
Long exposure time needed for photography
Cannot capture moving objects (blurring)
Image is always inverted
Cannot zoom
15.3.7 The Pinhole Camera and the Human Eye
Interestingly, our eyes work on a similar principle to a pinhole camera, but with a lens to focus more light :
| Pinhole Camera | Human Eye |
|---|---|
| Pinhole (aperture) | Pupil |
| Light-proof box | Eye socket/eyeball |
| Screen (tracing paper) | Retina |
| - | Lens (focuses light) |
| - | Iris (controls light entering) |
📝 PSTET Note: A real pinhole camera cannot gather enough light for quick photography, which is why modern cameras use lenses to focus more light onto the film or sensor .
15.3.8 Classroom Activity: Making a Pinhole Camera
| Step | Instructions |
|---|---|
| 1 | Take an empty cylindrical container (like a potato chip tube or tin can) |
| 2 | Paint the inside black (or line with black paper) |
| 3 | Make a small, clean pinhole in the center of the bottom using a pin |
| 4 | Cover the open end with tracing paper or butter paper (held by rubber band) |
| 5 | Take the camera to a bright area and point the pinhole toward a well-lit object |
| 6 | Look at the tracing paper screen—you'll see an inverted image! |
15.3.9 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Make Your Own | Students construct pinhole cameras from simple materials | Hands-on learning |
| Image Investigation | Students observe how image changes with pinhole size, distance | Scientific inquiry |
| Compare with Eye | Discuss similarities between pinhole camera and human eye | Cross-curricular connection |
| History of Photography | Brief discussion on how early photography used camera obscura (similar principle) | Historical context |
Section 15.4: Reflection of Light (Plane Mirror - Regular and Diffused)
Introduction
When you look into a mirror, you see yourself. When you look at a rough wall, you don't see your reflection. What causes this difference? The answer lies in reflection of light—the phenomenon that makes objects visible and allows us to see images .
15.4.1 What is Reflection of Light?
Definition: Reflection of light is the phenomenon of light bouncing back from the surface of an object after striking it .
How We See Non-luminous Objects:
We see most objects around us because light from a source falls on them, gets reflected, and enters our eyes .
15.4.2 Smooth vs. Rough Surfaces
| Surface Type | Reflection Property | Example |
|---|---|---|
| Smooth, shiny, polished surfaces | Reflect more light in a definite direction | Mirror, still water, polished metal |
| Rough, unpolished surfaces | Reflect less light and scatter it in all directions | Wall, paper, wood, cloth |
📝 PSTET Note: The best reflector of light is silver. For this reason, a thin layer of silver metal is deposited on one side of the glass plate while making a plane mirror. This silver coating is protected by red paint .
15.4.3 Laws of Reflection
The reflection of light is governed by two fundamental laws :
First Law: The incident ray, the reflected ray, and the normal (perpendicular to the surface at the point of incidence) all lie in the same plane.
Second Law: The angle of incidence is always equal to the angle of reflection.
Key Terms:
| Term | Definition |
|---|---|
| Incident ray | The light ray that strikes the surface |
| Point of incidence | The point where the incident ray meets the surface |
| Reflected ray | The light ray that bounces off the surface |
| Normal | An imaginary line perpendicular to the surface at the point of incidence |
| Angle of incidence (i) | The angle between the incident ray and the normal |
| Angle of reflection (r) | The angle between the reflected ray and the normal |
Diagram:
Normal
|
|
Incident | Reflected
ray | ray
\ | /
\ | /
\ | /
\ | /
\ | /
\ | /
\|/
----|---- Mirror surfaceMathematically:
∠i = ∠r
Special Case: When a ray of light falls normally (perpendicular) on the surface (angle of incidence = 0°), it is reflected back along the same path (angle of reflection = 0°) .
15.4.4 Types of Reflection
There are two main types of reflection :
A. Regular/Specular Reflection
Definition: Regular reflection occurs when light rays are reflected from a smooth, shiny, or polished surface like that of a mirror. The light rays are reflected by a definite angle .
Characteristics:
Incident parallel rays remain parallel after reflection
Reflected rays go in a specific direction
The angle of incidence equals angle of reflection for each ray
Forms clear images
Surfaces: Plane mirrors, calm water, polished metal
Example: When you look into a plane mirror, you see your own clear image because of regular reflection.
B. Diffused/Irregular Reflection
Definition: Diffused reflection occurs when light rays hit an irregular object with a rough surface and are scattered in all directions .
Characteristics:
Incident parallel rays are reflected in different directions
No definite angle of reflection (varies for each ray)
No image is formed
Surfaces: Paper, walls, wood, cloth, unpolished surfaces
Why We Can See Objects: Diffused reflection is actually what makes most objects visible to us. If all surfaces were perfectly smooth like mirrors, we would only see reflected light sources, not the objects themselves .
Comparison Table:
| Feature | Regular/Specular Reflection | Diffused/Irregular Reflection |
|---|---|---|
| Surface | Smooth, polished | Rough, irregular |
| Reflected rays | Parallel (for parallel incident rays) | Scattered in all directions |
| Image formation | Clear image formed | No image formed |
| Example | Mirror, calm water | Wall, paper, cloth |
15.4.5 Reflection from a Plane Mirror
A plane mirror is a mirror with a flat (planar) reflective surface .
A. Image Formation in a Plane Mirror
How the Image is Formed:
| Step | Process |
|---|---|
| 1 | Light rays from an object strike the plane mirror |
| 2 | Each ray obeys the laws of reflection |
| 3 | The reflected rays enter our eyes |
| 4 | Our brain traces these rays back in straight lines behind the mirror |
| 5 | The rays appear to come from a point behind the mirror—this is the image |
B. Characteristics of Image Formed by Plane Mirror
| Characteristic | Description |
|---|---|
| Nature | Virtual (cannot be projected on a screen) |
| Orientation | Erect (upright) |
| Size | Same size as the object |
| Distance | Image distance = Object distance (behind the mirror) |
| Lateral inversion | Left appears right; right appears left |
| Magnification | 1 (unit magnification) |
📝 PSTET Note: The image in a plane mirror is called virtual because light rays do not actually meet at the image location; they only appear to come from there. A virtual image cannot be obtained on a screen .
C. Lateral Inversion Explained
Definition: Lateral inversion is the phenomenon where the left side of an object appears as the right side in the image, and vice versa.
Examples:
If you raise your left hand in front of a mirror, the image appears to raise its right hand
The word "AMBULANCE" is written in reverse on the front of ambulances so that drivers in rearview mirrors see it correctly (AMBULANCE)
Why Does This Happen?
Because the image is formed by reflection, the front and back relationship is preserved, but left and right get swapped.
15.4.6 Multiple Reflections
When two mirrors are placed at an angle, multiple images can be formed.
| Angle Between Mirrors | Number of Images | Formula |
|---|---|---|
| 90° | 3 | n = 360/θ - 1 |
| 60° | 5 | n = 360/θ - 1 |
| 45° | 7 | n = 360/θ - 1 |
| 0° (parallel) | Infinite | - |
Formula: Number of images (n) = (360° ÷ θ) - 1, where θ is the angle between mirrors.
Kaleidoscope: Uses multiple reflections to create beautiful patterns.
15.4.7 Uses of Plane Mirrors
| Use | Application |
|---|---|
| Dressing mirrors | Personal grooming (bathrooms, bedrooms) |
| Rear-view mirrors | In vehicles to see traffic behind |
| Side mirrors | In vehicles for side visibility |
| Periscopes | To see over obstacles (submarines, tanks) |
| Kaleidoscopes | To create symmetrical patterns |
| Jewelry shops | Multiple mirrors to make shop appear larger and showcase items |
| Blind turns on roads | Convex mirrors often used, but plane mirrors also used at some locations |
15.4.8 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Mirror Exploration | Students explore their own reflections in plane mirrors | Personal discovery |
| Lateral Inversion Activity | Write words on transparency; view in mirror to see inversion | Hands-on learning |
| Reflection Ray Diagram | Students draw ray diagrams showing incident/reflected rays | Visual representation |
| Multiple Mirror Play | Place two mirrors at different angles; observe multiple images | Engaging exploration |
| "Why AMBULANCE?" Discussion | Discuss why ambulance lettering is reversed | Real-world application |
Chapter Summary: Key Points for Revision 📝
Quick Revision Table
Practice Zone: PSTET-Style Questions 🎯
Content-Based MCQs
Q1. Which of the following is a luminous object?
a) Moon
b) Table
c) Sun
d) Book
Q2. The Moon is visible to us because it:
a) Produces its own light
b) Reflects light from the Sun
c) Reflects light from the Earth
d) Emits light at night
Q3. Which type of material allows light to pass through partially but scatters it?
a) Transparent
b) Translucent
c) Opaque
d) Luminous
Q4. A shadow is formed because:
a) Light travels in curved lines
b) Light travels in straight lines and is blocked by an object
c) Objects absorb all light
d) Light reflects from surfaces
Q5. Which object CANNOT cast a shadow?
a) Wooden block
b) Glass tumbler (clear)
c) Book
d) Metal coin
Q6. The image formed in a pinhole camera is:
a) Erect and same size
b) Inverted and laterally reversed
c) Erect and magnified
d) Inverted and diminished always
Q7. According to the laws of reflection, the angle of incidence is:
a) Greater than angle of reflection
b) Less than angle of reflection
c) Equal to angle of reflection
d) Not related to angle of reflection
Q8. Which type of reflection occurs from a rough surface like a wall?
a) Regular reflection
b) Specular reflection
c) Diffused reflection
d) No reflection
Q9. The image formed by a plane mirror is:
a) Real and inverted
b) Virtual and erect
c) Real and erect
d) Virtual and inverted
Q10. If you stand 2 meters in front of a plane mirror, how far behind the mirror does your image appear?
a) 1 meter
b) 2 meters
c) 4 meters
d) Depends on mirror size
Pedagogical MCQs
Q11. A teacher wants to demonstrate that light travels in straight lines. The best activity would be:
a) Show a diagram in textbook
b) Arrange three cardboard sheets with aligned holes and show light passing through
c) Lecture about rectilinear propagation
d) Show a video of laser light
Q12. To teach the difference between transparent, translucent, and opaque materials, a teacher should:
a) Give definitions for students to memorize
b) Provide various materials and torches for students to test and classify
c) Show pictures of different materials
d) Read descriptions from textbook
Q13. A student asks, "Why is the word AMBULANCE written backwards on the front of the vehicle?" The correct explanation is:
a) "It looks fancy"
b) "So that drivers in rearview mirrors see it correctly due to lateral inversion"
c) "To confuse people"
d) "It's a medical symbol"
Q14. While teaching pinhole camera, the most effective approach is:
a) Show a diagram and explain
b) Have students make their own pinhole cameras and observe images
c) Show a video of how cameras work
d) Give notes to memorize
Q15. A teacher observes that students think shadows are "things" that exist independently. To address this misconception, the teacher should:
a) Ignore it
b) Explain that shadows are absence of light and cannot exist without object and light source
c) Give a written test
d) Show more pictures of shadows
Answer Key with Explanations
Pedagogical Reflection for Teachers 🤔
Think-Pair-Share Activity:
Think: How would you explain to students why we can see a book in a well-lit room but not in complete darkness?
Pair: Discuss with a colleague how you would set up a "Light Learning Corner" with activities for each section of this chapter.
Share: Design a 15-minute activity to teach the laws of reflection using simple mirrors and torches.
NCERT Textbook Linkages 📚
| Class | Chapter | Topic |
|---|---|---|
| Class 6 | Chapter 11 | Light, Shadows and Reflections |
| Class 7 | Chapter 15 | Light |
| Class 8 | Chapter 16 | Light |
| Class 10 | Chapter 10 | Light – Reflection and Refraction |
Chapter End Notes
Key Terminology Glossary
Quick Tips for PSTET Aspirants ⚡
✅ Memorize with Mnemonics:
Luminous vs. Non-luminous: "Luminous = Light self; Non-luminous = No light self"
Transparent, Translucent, Opaque: "Through (clear), Through (fuzzy), Out (blocked)"
Laws of Reflection: "In Reflection, Angles Equal" = Incident ray, Reflected ray, Angles Equal
Plane Mirror Image: "Virtual Erect Same Distance Lateral" = Virtual, Erect, Same size, same Distance, Lateral inversion
✅ Common Exam Traps:
Diffused reflection still follows laws—each ray individually obeys laws, but surfaces are irregular
✅ Important Facts:
Light speed = 3 × 10⁸ m/s in vacuum
Number of images formula: n = 360/θ - 1
Sun is primary natural light source
Answers to "Check Your Understanding"
[To be filled by student]
📝 Note for Self-Study: After completing this chapter, ensure you can:
Give 5 examples each of luminous and non-luminous objects
Explain why the Moon is non-luminous
Define and give examples of transparent, translucent, and opaque materials
Explain how shadows are formed with conditions required
Describe how a pinhole camera works and why the image is inverted
State the two laws of reflection
Differentiate between regular and diffused reflection with examples
List 5 characteristics of image formed by plane mirror
Explain lateral inversion with real-life example
Perform simple ray diagrams for reflection
