Page 1 - Lesson notes- Introduction to light

SAI INTERNATIONAL SCHOOL

Class 6
Lesson notes
Subject- Physics
Ch. - Light, Shadows and Reflection

Subtopic- Introduction to Light

Light: light is a form of energy, which causes a sensation of vision.

Properties of light:

« It is a form of energy.
« It can travel through vacuum.
« Light always travels in straight path.
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« Speed of light is 3×10 m/s
« It is the travels fastest in the universe.

Importance of light:

« Light is essential for the existence of life.
« Light is responsible for warmth of earth.
« Sunlight is used by plants for photosynthesis and stimulation/growth.
« Light is also responsible for food chain.

Note:

• Natural light, often referred to as white light, is actually composed of different
colors.
• The reflected colour decides the colour of the object as we see.
For example- grass looks green because it absorbs all the colours except green. It
reflects back the green colour that is received by our eyes.

History of Light

• Ancient Greece: Euclid studied straight-line light travel.
• Isaac Newton: Proved white light has many colours.
• Newton’s Prism: First to show that sunlight splits into a rainbow.
• 1801: Thomas Young proved light shows wave behaviour.
• 1905: Einstein explained light as particles (called photons)—this helped
invent solar panels!