Light
Energy
- Properties of light:
Light travels in straight lines, has a specific speed, and exhibits both
particle and wave behaviours.
- Transmission of light:
Light interacts with different materials, being absorbed, transmitted, or
reflected, affecting visibility.
- Shadows: Shadows are created when objects block
light, with their size and shape influenced by the light source and the
object's distance.
- Eclipses: Solar and lunar eclipses occur when the
Earth, Moon, and Sun align, causing shadows on the Earth or the Moon.
Reflection
and Refraction of Light
- Reflection of light:
Light bounces off surfaces, following the law of reflection, where the
angle of incidence equals the angle of reflection.
- Refraction of light:
Light changes direction when passing through different mediums, like air
and water, resulting in bending and focusing effects.
Images
- Virtual images:
Virtual images are formed in plane mirrors and appear upright and
laterally inverted, but cannot be projected onto a screen.
- Real images: Real
images are formed by concave mirrors or converging lenses, allowing them
to be projected onto a surface.
The Eye
- Structure and parts of the eye: The
eye is composed of parts like the cornea, lens, retina, and optic nerve,
each playing a vital role in vision.
- Power of accommodation and persistence of vision: The eye adjusts to focus on objects at different distances, and
the brain briefly retains images, enabling motion perception.
- Common eye defects:
Vision problems like myopia (near-sightedness) and hyperopia
(farsightedness) are common and can be corrected with glasses, contact
lenses, or surgery.
Dispersion
of Light and Colours
- Colours in white light:
White light is made up of various colours, which can be separated into a spectrum
when passed through a prism.
- Colours of objects:
Objects appear certain colours depending on the wavelengths of light they
reflect or absorb.
Useful
Inventions and Applications of Light
- Compound microscope:
Microscopes magnify small objects using multiple lenses, revealing details
invisible to the naked eye.
- Telescope: Telescopes collect and focus light from
distant celestial objects, allowing us to observe stars, planets, and
more.
- Camera: Cameras capture images by focusing
light onto light-sensitive surfaces, using lenses and apertures.
- Fiber optics:
Light is transmitted through optical fibres to carry data over long
distances at high speeds.
- Satellites:
Satellites use light, in the form of electromagnetic waves, for
communication, weather forecasting, and space exploration.
- X-ray: X-rays are used in medical imaging to
see inside the body, particularly for detecting fractures and other
issues.
- Optical smoke detector:
Smoke detectors use light to identify smoke particles and trigger alarms
in case of fire.
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