TOPIC 42 OF 46

Light, Shadows and Reflections

🎓 Class 7 Science CBSE Theory Ch 11 — Light: Shadows and Reflections ⏱ ~8 min
🌐 Language: [gtranslate]

This MCQ module is based on: Light, Shadows and Reflections

[myaischool_lt_science_assessment grade_level="class_7" science_domain="physics" difficulty="basic"]

Chapter 11 at a Glance — Light: Shadows and Reflections

Sources of Light

Natural (Sun, stars, fireflies) or artificial (candle, bulb, torch) — both emit light of their own.

Luminous / Non-luminous

Luminous objects produce their own light; non-luminous only reflect it (Moon, book, wall).

Transparent

Almost all light passes through (clean glass, water, air).

Translucent

Only some light passes through; objects appear blurred (butter paper, frosted glass).

Opaque

No light passes through; light is blocked or reflected (wood, metal, stone).

Straight-line Travel

Light travels in a straight line in any uniform medium — the rectilinear propagation of light.

Shadow

Dark patch formed when light, an opaque object and a screen come together. Always black — just absence of light.

Shadow Size

Object near the source → large shadow; object near the screen → small, sharp shadow.

Pinhole Camera

Produces an inverted, smaller image of a bright object because light crosses through a tiny hole.

Eclipses

Sun–Moon–Earth alignment creates cosmic shadows: solar (Moon between) and lunar (Earth between).

Reflection

Bouncing back of light from a smooth surface. Angle of incidence = angle of reflection.

Plane Mirror Image

Virtual, erect, same size, equal distance behind, laterally inverted.

Periscope

Two plane mirrors at 45° let us look over walls and from submarines.

Kaleidoscope

Three mirrors in a triangular tube give ever-changing symmetric colour patterns.

Rainbow

Sunlight split by raindrops into seven colours — VIBGYOR.

Keyword Dictionary

LuminousObject that emits its own light.
Non-luminousObject seen only by reflected light.
TransparentLets nearly all light pass through.
TranslucentLets only some light pass, blurred view.
OpaqueBlocks all light; no view through.
ShadowDark area formed behind an opaque object.
RectilinearTravelling in a straight line.
Pinhole cameraBox with tiny hole that forms inverted images.
Solar eclipseMoon's shadow on Earth (new moon).
Lunar eclipseEarth's shadow on Moon (full moon).
ReflectionBouncing back of light from a surface.
NormalLine drawn at 90° to the mirror at the point of incidence.
Angle of incidenceAngle between incident ray and the normal.
Plane mirrorFlat reflecting surface; gives virtual, erect, same-size image.
Lateral inversionLeft–right swap in a mirror image.
PeriscopeTwo-mirror device to see around obstacles.
KaleidoscopeThree-mirror tube showing symmetric colour patterns.
VIBGYORViolet, indigo, blue, green, yellow, orange, red — colours of a rainbow.

NCERT Exercises — Solved

Q1. Distinguish between a luminous and a non-luminous object with one example each.

A luminous object produces light of its own — for example, the Sun or a lit candle. A non-luminous object does not produce light; we see it only when light from a luminous object falls on it and reflects into our eyes — for example, the Moon or a book.

Q2. Classify the following as transparent, translucent or opaque: clear glass, butter paper, wooden door, air, frosted bathroom glass, a thick curtain.

Transparent: clear glass, air. Translucent: butter paper, frosted bathroom glass. Opaque: wooden door, thick curtain.

Q3. State the three conditions needed for a shadow to form.

To form a shadow we need: (i) a source of light, (ii) an opaque object in the path of the light, and (iii) a screen (wall, floor or ground) behind the object on which the shadow can fall. Remove any one and no shadow will appear.

Q4. Why does a shadow always appear black even when the object has a bright colour?

The shadow is the region on the screen where no light reaches because the opaque object blocks it. Our eyes interpret the absence of light as black. The colour, design or texture of the object plays no role because light never passes through it to carry that colour onto the screen.

Q5. A boy holds a cardboard cut-out in front of a torch. When he moves the cut-out closer to the torch, what happens to its shadow on the opposite wall? Explain.

The shadow becomes larger. As the cut-out moves towards the torch, the rays that just miss its edges have a longer distance left to travel before they reach the wall, so they spread wider. The dark patch on the wall is therefore bigger. It is also a little fuzzy because the torch bulb is not a true point source.

Q6. Describe how a pinhole camera forms an image. Why is the image inverted?

A pinhole camera is a closed dark box with a tiny hole on one side and a translucent screen on the opposite side. Because light travels in straight lines, only the narrow ray from each point of the object that passes through the pinhole reaches the screen. A ray from the top of the object goes downward through the hole and lands at the bottom of the screen; a ray from the bottom goes upward through the hole and lands at the top. Similarly left and right are swapped. The image is therefore small, coloured and inverted.

Q7. State the two laws of reflection of light. Draw a labelled ray diagram.

Law 1: The angle of incidence is equal to the angle of reflection, \(i = r\).
Law 2: The incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.

incident reflected normal i r

Q8. List any four properties of the image formed by a plane mirror.

(i) The image is virtual — it cannot be caught on a screen. (ii) The image is erect — the same way up as the object. (iii) The image is of the same size as the object. (iv) The image is formed as far behind the mirror as the object is in front. (v) The image is laterally inverted — left-to-right swapped.

Q9. Why is the word AMBULANCE written in reverse on the bonnet of an ambulance?

A plane mirror produces a laterally inverted image. When a driver in front of the ambulance looks into his rear-view mirror, he sees the writing laterally inverted once more — the two reversals cancel out and he reads it correctly as "AMBULANCE". This helps him get out of the way quickly.

Q10. Explain the working of a simple periscope with a clear diagram.

A periscope is a long hollow tube with two plane mirrors, each tilted at 45° to the length of the tube, facing each other. Light from an object outside hits the upper mirror at 45°; by the law of reflection, it bounces downward through the tube. It then hits the lower mirror at 45° and bounces outward into the observer's eye. The two reflections together bend the light through 180° (two 90° turns), so the observer sees an object above an obstacle without having to raise his head.

Q11. What is an eclipse? Give the difference between a solar and a lunar eclipse.

An eclipse is a shadow-event in the sky formed when the Sun, Moon and Earth line up in a straight line.
Solar eclipse: The Moon comes between the Sun and the Earth, and its shadow falls on the Earth. It occurs on a new-moon day.
Lunar eclipse: The Earth comes between the Sun and the Moon, and Earth's shadow falls on the Moon, making the Moon appear dark or reddish. It occurs on a full-moon night.

Q12. Write the names of the seven colours of a rainbow in the correct order from the outer edge to the inner edge of the arc.

From outside to inside, the order is Red, Orange, Yellow, Green, Blue, Indigo, Violet. Remembered as ROYGBIV or its reverse VIBGYOR. These colours are produced when sunlight is split by tiny water drops after rain.

Frequently Asked Questions — Light, Shadows and Reflections — Chapter 11 Exercises

What does the topic 'Light, Shadows and Reflections — Chapter 11 Exercises' cover in Class 7 Science?

The topic 'Light, Shadows and Reflections — Chapter 11 Exercises' is part of NCERT Class 7 Science Chapter 11 — Light: Shadows and Reflections. It covers the key ideas of light, shadows, reflection, mirrors, NCERT exercises, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.

Why is 'Light, Shadows and Reflections — Chapter 11 Exercises' important for Class 7 NCERT Science?

'Light, Shadows and Reflections — Chapter 11 Exercises' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 11 — Light: Shadows and Reflections — introduces light and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.

What are the key concepts students should remember from Light, Shadows and Reflections — Chapter 11 Exercises?

The key concepts in 'Light, Shadows and Reflections — Chapter 11 Exercises' for Class 7 Science are: light, shadows, reflection, mirrors, NCERT exercises. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 11 will help students retain these concepts for unit tests and the annual CBSE examination.

How is Light, Shadows and Reflections — Chapter 11 Exercises taught using activities in NCERT Curiosity Class 7?

NCERT Curiosity Class 7 Science teaches 'Light, Shadows and Reflections — Chapter 11 Exercises' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 11 — Light: Shadows and Reflections — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.

How should Class 7 students prepare for the Chapter 11 exercises?

To prepare for the Chapter 11 — Light: Shadows and Reflections — exercises in NCERT Class 7 Science, students should first revise the theory in Parts 1–3 and make a short list of definitions and diagrams for light, shadows, reflection, mirrors, NCERT exercises. Next, attempt each exercise question on their own before checking the solution. Pay extra attention to MCQs, assertion–reason questions and short-answer items, as these appear in CBSE competency-based tests. Practising with the NCERT Curiosity textbook, the exemplar questions, and the MyAiSchool practice bank helps Class 7 students score better in unit tests and the annual examination.

How does 'Light, Shadows and Reflections — Chapter 11 Exercises' connect to other chapters of Class 7 Science?

'Light, Shadows and Reflections — Chapter 11 Exercises' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of light appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 11 — Light: Shadows and Reflections — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.

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