CBSE Class 7 · Science
Light: Shadows and Reflections
Official NCERT chapter from Curiosity (book code gecu1). ExamMaster notes are original teaching at CBSE Class 7 depth.
This lesson follows the official chapter “Light: Shadows and Reflections” in Curiosity. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.
- CBSE Class 7
- Easy level
- 8 concepts
1Sources of Light
A source of light is something that sends light you can see by: the Sun, a lamp, a flame as taught. The Moon is usually a reflector in the school story — name the lesson’s sort if it distinguished them.
A white wall in a dark room is not a source.
Figure. A source makes its own light. The Sun does. The Moon is bright because sunlight reaches it and comes on to your eye — it is not a second lamp.
How it works
- Ask: does it send light, or only bounce it?Source, or not.
- Name a source you can point toSun, lamp.
- Keep the wall as a bounce if that is the lessonA sort.
2Does Light Travel in a Straight Line?
Light travelling in a straight line is the pinhole-and-shadow reason: a sharp shadow and a pinhole image sit on straight paths. A curved-ray doodle needs a reason this class did not give.
A garden hose is not a light-path.
Figure. Light from the lamp reaches the eye only when the three holes sit on one straight line. Shift one card and the path is blocked — that is the straight-line test, not a slogan.
How it works
- See a sharp shadow or a pinhole spotEvidence.
- Draw the path as a straight line from source through the edge or holeThe model.
- Keep the model at those looksStraight here.
3Light through Transparent, Translucent and Opaque Materials
Transparent lets a sharp view; translucent a glow without a sharp view; opaque a block. Hold the sample between eye and lamp (safely). Colour of a frame is not the test.
A painted border can be opaque while the pane is transparent.
Figure. Transparent glass lets the ray through. Translucent frosting lets light through but breaks the sharp path. Opaque wood stops the ray and a shadow sits behind it.
How it works
- Place the sample between eye and lightThe test.
- Ask: sharp view, glow-only, or blockThree buckets.
- Name that bucketThis pane, this tracing sheet, this wood.
4Shadow Formation
A shadow is a dark patch where an opaque (or mostly blocking) object stops light that was travelling straight. The shadow sits on the screen opposite the source. A coloured drawing of a “shadow” that sits beside the lamp is a miss.
A second lamp can wash a shadow — that is another source, not a failure of the first.
Figure. A shadow needs a lamp, an opaque object, and a screen. The dark patch on the screen is the set of points the object keeps the lamp from reaching. Move the object nearer the lamp and that patch grows.
How it works
- Place source, object, screenThe three.
- See the dark patch on the far side of the objectThe shadow.
- Move the object; the patch should obey the straight pathsThe test.
5Reflection of Light
Reflection is light bouncing from a surface. A smooth shine (as taught) gives a more regular bounce; a rough wall scatters. The heading uses the lesson’s reflection-word — bounce is the job.
A black cloth that eats light is a weak bounce, not a proof light failed to travel.
Figure. The dashed normal stands perpendicular to the mirror. Incidence and reflection are both 45° from that normal, so the two angles are equal. The law is about those angles, not about a pretty bounce.
How it works
- Send light to a surfaceThe meet.
- See it leave at a bounce you can argueReflection as taught.
- Keep mirror-bounce and wall-scatter as two looks if the lesson split themSame job, different surface.
6Images Formed in a Plane Mirror
A plane mirror gives an image you cannot catch on a card the way a pinhole spot sits — it is a looking-image: same size (as taught), left-right swap as the lesson named, as far behind as you are in front. The image is a rule, not a tiny person in the glass.
Reaching into the glass to grab the image is the miss.
Figure. The image sits as far behind the mirror as the object sits in front, and it is erect and the same size. Left and right swap: that is lateral inversion, not a change of height.
How it works
- Stand in frontObject-distance.
- See the looking-imageThe rule’s object.
- Name same-size and the taught left-right notePlane-mirror jobs.
7Pinhole Camera
A pinhole camera is a dark box, a small hole, and a screen. Light through the hole makes an inverted spot-picture. It is a straight-line look, not a phone.
A large window is not a pinhole.
Figure. Rays from the top of the object through the hole land at the bottom of the screen, and the bottom lands at the top. The image is real, inverted, and smaller when the object is farther from the hole.
How it works
- Dark box, small hole, screenThe three.
- A bright object outsideThe source-side.
- See an inverted picture on the screenThe pinhole job.
8Making Some Useful Items
Useful items here are things you make to run a look: a pinhole box, a simple periscope as taught, a shadow-puppet screen. Useful means the look works, not a craft grade.
A decorated box that leaks light is not useful for the pinhole job.
Figure. A periscope is two parallel mirrors at 45°. A level ray in reflects down the tube and out again still level. Each bounce uses the same incidence–reflection rule you already drew.
How it works
- Name the item and its lookPinhole, periscope, puppet.
- Build so the path does the jobThe useful test.
- If the look fails, mend the gap or the holeCraft serves the science.
A shadow forms
- On the far side of a blocking object, from straight paths
- On the lamp itself
- Only in a plane mirror
Source, object, screen.
Notes
- Mapped to the official NCERT chapter “Light: Shadows and Reflections”. Original teaching only — no textbook sentences.
- Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.
Recap
Hold these pegs from the official chapter “Light: Shadows and Reflections”. The wording is ExamMaster’s teaching, not a textbook recap.
- Sources of Light
- A source of light is something that sends light you can see by: the Sun, a lamp, a flame as taught.
- Does Light Travel in a Straight Line?
- Light travelling in a straight line is the pinhole-and-shadow reason: a sharp shadow and a pinhole image sit on straight paths.
- Light through Transparent, Translucent and Opaque Materials
- Transparent lets a sharp view; translucent a glow without a sharp view; opaque a block.
- Shadow Formation
- A shadow is a dark patch where an opaque (or mostly blocking) object stops light that was travelling straight.
- Reflection of Light
- Reflection is light bouncing from a surface.
- Images Formed in a Plane Mirror
- A plane mirror gives an image you cannot catch on a card the way a pinhole spot sits — it is a looking-image: same size (as taught), left-right swap as the lesson named, as far behind as you are in front.
Practise Light: Shadows and Reflections
Reading is free and needs no account. Practice, mocks and progress live in the app.
- A 4-question practice set that ends the chapter
- 1 quick check with worked explanations
- Timed mocks scored with the real marking scheme
- Readiness tracked per topic, kept on your device