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Light: Shadows and Reflections – Class 7 Science notes, important questions and MCQs

NCERT Class 7 Science, chapter 11. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Light travels in straight lines. When an opaque object blocks it, a shadow forms; when light hits a shiny surface, it reflects.

Shadows

Materials: transparent (glass), translucent (butter paper), opaque (wood).
A shadow forms when an opaque object blocks light; it is always on the side opposite the light source.
A pinhole camera forms an inverted image because light travels in straight lines.

Reflection

Smooth shiny surfaces like mirrors reflect light regularly.
Plane mirror image: erect, same size, behind the mirror, left–right reversed.
Periscopes use two mirrors to see over obstacles.

Key terms

Opaque: does not let light pass through
Translucent: lets light pass partly
Reflection: bouncing back of light from a surface

Formulas

Angle of incidence = angle of reflection

Important questions with answers

Classify glass, wood and butter paper as transparent, translucent or opaque.2 marks

Glass: transparent. Butter paper: translucent. Wood: opaque.

Write three features of an image formed by a plane mirror.3 marks

It is virtual and erect, the same size as the object, as far behind the mirror as the object is in front, and laterally inverted.

What is a pinhole camera? Explain how it forms an image and give the nature of the image. Why is the word AMBULANCE written in reverse on vehicles?5 marks

A pinhole camera is a closed box with a tiny hole on one side and a translucent screen (tracing paper) on the other. Light rays from the object travel in straight lines through the hole and form an image on the screen. The image is real and inverted. AMBULANCE is written in reverse so that drivers ahead see it correctly in their rear-view mirrors, which laterally invert it, and make way.

Quick revision

Light travels in straight lines.
Opaque objects make shadows.
Mirror image is laterally inverted.

Exam tips

Shadow size changes with the distance between the object and the light source.
Solar and lunar eclipses are shadows of the Moon and Earth.

Practice MCQs

Which is opaque?
1. glass
2. clear water
3. wooden board
4. cellophane
Show answer
Answer: (c) wooden board. Blocks light.
Light travels in
1. curves
2. straight lines
3. circles
4. zigzags only
Show answer
Answer: (b) straight lines. Rectilinear propagation.
The image in a pinhole camera is
1. erect
2. inverted
3. coloured differently
4. magnified only
Show answer
Answer: (b) inverted. Rays cross at the pinhole.
A periscope works using
1. two plane mirrors
2. lenses only
3. prisms only
4. a screen
Show answer
Answer: (a) two plane mirrors. Mirrors at 45°.
A shadow is formed when light is blocked by
1. a transparent object
2. a mirror only
3. an opaque object
4. air
Show answer
Answer: (c) an opaque object. Light cannot pass through.
A solar eclipse happens when
1. Earth comes between Sun and Moon
2. clouds cover the Sun
3. the Sun is between Earth and Moon
4. the Moon comes between Sun and Earth
Show answer
Answer: (d) the Moon comes between Sun and Earth. Moon's shadow falls on Earth.
The letter "R" in a plane mirror appears
1. laterally inverted
2. upside down
3. unchanged
4. smaller
Show answer
Answer: (a) laterally inverted. Left and right swap.
In a plane mirror, the image of the word "AMBULANCE" appears
1. upside down
2. laterally inverted
3. magnified
4. unchanged
Show answer
Answer: (b) laterally inverted. Left-right reversal, which is why it is written reversed on ambulances.

All chapters of Class 7 Science

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.