🎯 Learning outcomes
- Explain how shadows form and why light travels in straight lines
- Describe reflection and how sound travels through solids, liquids and gases
- Identify forces such as friction, gravity and magnetism in daily life
Before you start: Sources of light and sound; push and pull.
📖 Explanation
Light travels in straight lines, so an opaque object blocks it and forms a shadow. Shiny surfaces like mirrors reflect light, which is how we see our image. We see objects when light from them enters our eyes.
Sound is made by vibrations and needs a medium to travel: it moves through air, water and solids (you can hear a train through a rail). Sound cannot travel in empty space. Loudness depends on how big the vibration is; pitch on how fast it vibrates.
Friction is a force that slows moving things; it lets us walk without slipping. Gravity pulls things towards the Earth, so a ball falls. Magnets attract iron and have north and south poles: like poles repel, unlike poles attract.
The Konark Sun Temple in Odisha has huge stone wheels that act as sundials, showing time by the shadows cast by sunlight.
✗ We see things because light comes out of our eyes
✓ We see because light from the Sun or a lamp bounces off objects and enters our eyes.
🧪 Try this activity
Make a string telephone with two cups and a long thread. Find out whether sound travels better when the thread is tight or loose.
✍️ Question bank with answers
Tap an option to check multiple-choice answers. Open “Answer” or “Marking points” for the others.
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Sound cannot travel through
Answer
C. empty space
Sound needs a medium; space is empty.
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Which force makes a ball fall down?
Answer
A. gravity
The Earth pulls objects towards it.
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Two north poles of magnets
Answer
D. repel each other
Like poles repel.
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What does a mirror do to light?
Answer
reflects it
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Why do we not slip on a dry floor?
Answer
friction between our feet and the floor
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Why do we see the flash of lightning before we hear thunder?
Marking points
- Light travels much faster than sound
- Both happen at the same time
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Describe an experiment to show that light travels in a straight line.
Marking points
- Take three cards with holes and a candle
- Line up the holes; the flame is seen
- Move one card; the flame cannot be seen
- Light travels in a straight line
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Why do roads become dangerous to walk on when wet or oily?
Answer
- Water or oil reduces friction
- Feet and tyres slip more easily
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Draw a bar magnet with N and S poles and show what happens when N faces N.
Answer
- Labelled N and S
- Arrows showing the magnets pushing apart
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