CBSE Class 7 Science Revision Notes Chapter 11: Light – Shadows and Reflections

Light allows us to see objects and usually travels in a straight line.

When light is blocked, a shadow forms, while a shiny surface can change its direction through reflection.

Light reaches us from the Sun, stars, fire, electric lamps and certain living organisms such as fireflies. Some objects produce their own light, while others become visible only because they reflect light falling on them.

These CBSE Class 7 Science Revision Notes Chapter 11 follow the current 2026–27 chapter. Revise luminous and non-luminous objects, straight-line travel of light, transparent and opaque materials, shadows, reflection, plane-mirror images, lateral inversion, pinhole cameras, periscopes and kaleidoscopes.

Key Takeaways

• Luminous objects: They emit their own light.
• Straight-line travel: Light normally moves along a straight path.
• Shadow: It forms when an object blocks light from reaching a screen.
• Plane-mirror image: It is erect, same-sized, laterally inverted and cannot be obtained on a screen.

Access Class 7 Science Chapter 11 Light Shadows and Reflections Notes in 30 Minutes

Spend the first 10 minutes revising sources of light, luminous objects and the straight-line movement of light. Use the next 10 minutes for transparent, translucent and opaque materials, along with shadow formation.

Use the final 10 minutes to revise reflection, plane-mirror images, lateral inversion, pinhole cameras, periscopes and kaleidoscopes.

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Sources of Light in Class 7 Science Chapter 11 Notes

A source of light is an object or process that produces light. Sources may be natural or artificial.

The Sun is the main natural source of light for the Earth. Stars, lightning, natural fire and some living organisms also produce their own light.

Natural Sources of Light

Natural sources include:

• Sun
• Stars
• Lightning
• Natural fire
• Fireflies
• Some other light-producing organisms

Artificial Sources of Light

Humans first used fire for lighting and later developed oil lamps, wax candles, gas lamps and electric lights. Today, bulbs, tube lights, torches and LED lamps are widely used.

LED lamps consume less electricity and generally last longer than many traditional lamps. At the end of their useful life, they should be recycled or disposed of properly instead of being mixed with ordinary waste.

Luminous and Non-luminous Objects

Objects that produce their own light are called luminous objects. The Sun, stars, a burning candle and an electric bulb that is switched on are luminous.

Objects that do not produce their own light are called non-luminous objects. They are seen only when light from another source falls on them and reaches our eyes.

Why Does the Moon Shine?

The Moon is a non-luminous object. It does not produce its own visible light.

It appears bright because sunlight falls on its surface and is reflected towards the Earth.

Examples

A mirror reflects light strongly, but it does not produce light. It is therefore non-luminous.

Light Travels in a Straight Line

Light normally travels along a straight path. This property can be studied through simple activities using matchboxes, pipes or narrow openings.

The straight-line movement of light is also called the rectilinear propagation of light.

Matchbox Activity

Three matchboxes are arranged so that holes made in them are at the same height and lie in one straight line. A torch is placed at one end, while a screen is placed at the other.

When all holes are aligned, a bright spot appears on the screen. If one matchbox is moved sideways or vertically, the light spot disappears because the holes no longer provide a straight path.

Straight and Bent Pipe Activity

A candle flame can be seen through a straight hollow pipe. When the same pipe is bent, the flame is no longer visible through it.

This happens because light from the flame travels in a straight line and cannot follow the curve of the bent pipe.

Laser Beam in Water

A low-power laser beam can be made visible in water containing a small amount of milk. The visible beam follows a straight path through the water.

This activity must be performed only under teacher supervision. A laser beam should never be pointed at anyone’s eyes.

Transparent, Translucent and Opaque Materials

Materials can be grouped according to how much light passes through them. They may be transparent, translucent or opaque.

This classification helps us understand visibility and shadow formation.

Transparent Materials

Transparent materials allow almost all light to pass through them. Objects on the other side can usually be seen clearly.

Examples include:

• Clear glass
• Clean water
• Air
• Transparent plastic sheet

Translucent Materials

Translucent materials allow only part of the light to pass. Objects on the other side appear unclear or blurred.

Examples include:

• Tracing paper
• Frosted glass
• Thin cloth
• Oiled paper

Opaque Materials

Opaque materials do not allow light to pass through them. Objects behind them cannot be seen.

Examples include:

• Cardboard
• Wood
• Metal
• Stone
• Thick cloth

Comparison Table

Shadow Formation in Light Revision Notes

A shadow is a dark region formed when an object blocks light from reaching a surface. Since light travels in a straight line, the region behind the object receives less or no light.

The wall, floor, ground, paper or any other surface on which the dark region appears acts as a screen.

Conditions Needed for a Shadow

Three things are required to observe a shadow:

1. A source of light
2. An object in the path of light
3. A screen or surface

If any one of these is removed, the shadow cannot be observed properly.

Shadows of Different Materials

Opaque objects form dark and clear shadows because they block most of the light. Translucent objects form lighter shadows because some light passes through them.

Some transparent objects may also form faint shadows because they may absorb, scatter or reflect a small part of the light.

Factors Affecting a Shadow

The shape, size and sharpness of a shadow depend on the position of the source, object and screen. Moving any one of them may change the shadow.

The colour of an opaque object does not normally change the colour of its shadow. A red ball and a blue ball can both form dark shadows under the same white light.

Moving the Object Closer to the Torch

When an object is moved closer to the torch, it blocks a wider spread of light. The shadow usually becomes larger and may appear less sharp.

Moving the Object Closer to the Screen

When the object moves closer to the screen, the shadow usually becomes smaller and sharper.

Tilting the Object

Tilting or rotating an object changes the outline facing the light source. The shape of its shadow may therefore change.

Removing the Screen

Without a screen or surface, the shadow cannot be observed clearly even though the object continues to block light.

Using Two Torches

Two torches placed at different positions may produce two shadows. Each light source creates its own blocked region.

Why Does the Length of a Shadow Change?

The length of an outdoor shadow depends on the position of the Sun. When the Sun is low in the sky, shadows are long.

Around noon, the Sun is higher in the sky, so shadows are usually shorter. This is why a person’s shadow at 12 PM is often shorter than at 9 AM or 4 PM.

Reflection of Light

Reflection is the change in the direction of light when it strikes a shiny surface such as a plane mirror. The light continues travelling in a straight line before and after reflection, but its direction changes at the surface.

A shiny metal plate can also reflect light. Turning or tilting the plate changes the direction of the reflected beam and moves the bright spot on a nearby wall.

Mirror and Torch Activity

A thin beam of light can be produced using a torch and a narrow slit in a comb. When a plane mirror is placed in the beam’s path, the beam changes direction.

This shows that the mirror reflects the incoming light.

Why Can We See Objects in a Mirror?

Light falls on an object and is reflected towards the mirror. The mirror reflects this light towards our eyes.

Our brain interprets the light as if it is coming from behind the mirror, so an image appears there.

Images Formed by a Plane Mirror

An image formed by a plane mirror has several specific properties. These remain the same even when the object is moved closer to or farther from the mirror.

Same Size

The image formed by a plane mirror is the same size as the object. A pen appears to have an image of equal length.

Erect Image

The image is upright or erect. The top of the object remains at the top of the image.

Image Behind the Mirror

The image appears to be located behind the mirror. However, no actual object is present there.

Cannot Be Obtained on a Screen

A plane-mirror image cannot be captured on a screen placed in front of or behind the mirror. Such an image is called a virtual image.

Equal Distance

The image appears as far behind the mirror as the object is in front of it. If the object moves closer to the mirror, the image also appears closer.

Main Properties of a Plane-Mirror Image

Lateral Inversion

Lateral inversion is the apparent left-right reversal in a plane mirror. The left side of an object appears on the right side of the image, and the right appears on the left.

If you raise your left hand, the mirror image appears to raise its right hand. Similarly, touching your right ear appears as touching the left ear in the image.

Why Is AMBULANCE Written in Reverse?

The word AMBULANCE is often written in a laterally inverted form on the front of an ambulance. Drivers in vehicles ahead see it correctly in their rear-view mirrors.

This helps them recognise the emergency vehicle quickly and make way.

Do All Letters Look Different?

Letters with vertical symmetry may appear unchanged in a mirror. Examples include:

• A
• H
• I
• M
• O
• T
• U
• V
• W
• X
• Y

Many other letters and words appear reversed.

Aranmula Kannadi

Mirrors were once made by polishing stone and metal surfaces. In Kerala, the traditional Aranmula Kannadi is a special metal-surface mirror.

It reflects India’s long history of metal craftsmanship and mirror-making.

Pinhole Camera in Class 7 Science Chapter 11 Revision Notes

A pinhole camera is a simple device in which light from an object passes through a very small hole and forms an image on a screen.

It does not require a lens. Its working depends on the straight-line travel of light.

Simple Candle Activity

A small hole is made in a piece of cardboard, and a lighted candle is placed in front of it. A screen is placed behind the cardboard.

Light from the top of the flame travels through the hole to the lower part of the screen. Light from the lower part reaches the upper part of the screen, forming an inverted image.

Image Formed by a Pinhole Camera

The image is:

• Inverted
• Formed on a screen
• Usually coloured
• Affected by object and screen distances

Sliding Pinhole Camera

A simple pinhole camera can be made using two cardboard boxes that slide into each other. A small hole is made in one box, while tracing paper is fixed as the screen in the other.

The pinhole is pointed towards a bright outdoor object. Moving the inner box forward or backward helps obtain a clearer image on the tracing-paper screen.

Plane Mirror and Pinhole Camera Comparison

A plane mirror and pinhole camera both form images, but their image properties are different.

Periscope

A periscope is a device that uses two plane mirrors to allow a person to see an object that is not in the direct line of sight.

The mirrors are fixed inside a tube or box, usually at suitable angles. Light reflects from the upper mirror to the lower mirror and then reaches the observer’s eyes.

Uses of a Periscope

Periscopes are used:

• In submarines
• In tanks
• By soldiers in bunkers
• To look over walls
• To see above a crowd

The device works through two successive reflections.

Kaleidoscope

A kaleidoscope uses three plane mirrors arranged in a triangular form. Small coloured objects such as broken bangle pieces or beads are placed at one end.

Light reflected repeatedly between the mirrors forms several images. These repeated reflections create colourful and changing patterns.

Why Are the Patterns Different Every Time?

When the kaleidoscope is rotated, the coloured pieces change position. Their images and repeated reflections also change.

This produces a new pattern with each movement.

Uses

Kaleidoscopes are used for:

• Entertainment
• Studying multiple reflection
• Creating decorative designs
• Helping artists and designers develop patterns

Shadow Puppetry

Shadow puppetry uses flat cut-out figures placed between a light source and a screen. Moving the puppets creates the appearance of movement on the screen.

India has several traditional forms of shadow puppetry, including:

• Charma Bahuli Natya in Maharashtra
• Tholu Bommalata in Andhra Pradesh
• Togalu Gombeyaata in Karnataka
• Ravana Chhaya in Odisha
• Tholpavakoothu in Kerala
• Bommalattam in Tamil Nadu

These performances are used for entertainment, storytelling and sharing social messages.

Light, Fireflies and the Environment

Fireflies produce light through a chemical process inside their bodies. They use flashes of light to communicate.

Their numbers may decrease because of reduced forest cover, excessive tourism and artificial light at night.

What Is Light Pollution?

Light pollution is excessive or poorly managed artificial light. It can disturb:

• Fireflies
• Nocturnal animals
• Birds
• Insects
• Human sleep
• Natural night-time conditions

Responsible use of outdoor lighting can reduce these effects.

Better Lighting Practices

• Switch off unnecessary lights.
• Use downward-facing outdoor lights.
• Avoid extremely bright lights in natural areas.
• Use energy-efficient lamps.
• Recycle LED lamps properly.

Light from the Sun

Sunlight takes about 8 minutes and 20 seconds to reach the Earth. This means that we see the Sun as it appeared a little over eight minutes earlier.

The Sun is the main source of natural light and energy for the Earth.

Class 7 Science Chapter 11 Summary Notes

Important Terms from Light: Shadows and Reflections

Light source: An object or process that produces light.

Luminous object: An object that emits its own light.

Non-luminous object: An object that does not emit its own light.

Transparent material: A material that allows almost all light to pass.

Translucent material: A material that allows only some light to pass.

Opaque material: A material that blocks light.

Shadow: A dark region formed when an object blocks light.

Screen: A surface on which a shadow or image can be observed.

Reflection: Change in the direction of light after striking a surface.

Plane mirror: A flat reflecting surface.

Object: The actual item placed in front of a mirror or camera.

Image: The visual representation formed by reflected or transmitted light.

Erect image: An upright image.

Virtual image: An image that cannot be obtained on a screen.

Lateral inversion: Apparent left-right reversal in a mirror.

Pinhole camera: A device that forms an inverted image through a tiny opening.

Periscope: A device using mirrors to view objects outside the direct line of sight.

Kaleidoscope: A device that forms patterns through multiple reflections.

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