2. What basically is Light?
• Light is electromagnetic radiation within a certain portion of
the electromagnetic spectrum. The word usually refers to
visible light, which is visible to the human eye and is
responsible for the sense of sight.
• It doesn’t need a medium to travel in.
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3. Luminous objects!
• Any object is considered luminous if it emits its own light,
either through stored energy or energy supplied to the object,
which contrasts with non-luminous objects
• The Sun, the hot gases in a flame and the hot filament of a
bulb are some luminous objects around us.
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4. Non-luminous objects!
• Objects that do not give out their own light are known as
non-luminous.
• They can only be seen when light falling on them reflects into
our eyes.
• The moon and earth are examples of non-luminous objects.
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5. Opaque Materials
• Opaque materials do not allow light to pass through them.
• Wood, metals, ceramics and certain plastics are some examples
of opaque materials.
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6. Transparent Materials
• Transparent materials allow almost all the light to pass
through them.
• This allows us to see through objects.
• Glass, water and air are some examples of transparent
materials.
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7. Translucent Materials
• Translucent materials allow some light to pass through them.
• We can’t see clearly through them.
• Objects behind these materials look blur.
• Frosted glass, tracing paper and rice paper are translucent
materials.
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8. SHADOWS….!
• Shadows are formed when light is blocked by an opaque object,
• Light cannot bend round the opaque object because it travels in
straight lines.
• Thus, a region of darkness behind the object, called a shadow is
formed.
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9. Solar Eclipse
• As seen from the Earth, a solar eclipse is a type of eclipse that occurs
when the Moon passes between the Sun and Earth, and the Moon fully
or partially blocks the Sun.
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10. Lunar eclipse
•A lunar eclipse occurs when the Moon passes directly behind the Earth
into its umbra (shadow).
•This can occur only when the sun, Earth and moon are aligned exactly,
or very closely so, with the Earth in the middle.
•Hence, a lunar eclipse can occur only the night of a full moon.
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11. The Pinhole Camera
• A pinhole camera consists of a box with a small pinhole on one side
and a translucent screen or photographic film on the opposite side.
• It works on the principle that light travels in straight lines.
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