Light
Aim:
Investigate the transmission of light in different medium
•
Transparent. Translucent and Opaque objects
•
Different types of beams
•
Reflection and refraction
Revision:
1. What is natural light and Artificial light.
2. What is the benefits of natural light compared to artificial light.
3. Problems associated with poor lighting.
4. Distinguish between type of artificial lights.
What is light?
Light is form of energy required to see to live comfortably and work
efficiently.
Natural lighting:
The Sun produces natural light. This light source is only available between
sunrise and sun set hours, when sun light is not available artificial light is
required.
Artificial Lighting:
This is any light that is manmade, for example light from fires, candle and
electrical lamps. Artificial light is costly in comparison to natural light,
which is free of charge.
Benefits of Natural compared to artificial light:
Natural light is free of charge and this source of energy does not pollute the
environment, in comparison to the Artificial light source. Artificial light is a
utility that is costly, and the production of electricity is highly toxic to the
environment, since it entails the burning of natural gas.
To maximise the use of natural light, buildings and houses must be
constructed strategically to access Sun light. Therefore, the placement of
doors and windows will help reduce the use of artificial light which is
reducing the use of electricity.
Problems associated with poor lighting:
Doing work or reading in a poorly lite room, is very uncomfortable and
damaging to the eyes of all ages and cause headaches.
Are there different types of artificial light?
Filament lamps
1. Energy is wasted as heat so they are
not very efficient
2. Expensive to run
3. Do not cost as much
4. Do not last very long
5. Only available as conventional light
bulbs
6. Cause sharp shadows
Fluorescent tubes
1. Not much energy is wasted as heat so
they are more
2. Much cheaper to run than filament
lamps
3. Cost more to buy
4. Long lasting
5. Can be made into low energy lamps
6. Do not cause sharp shadows,
produce a soft lighting effect
Define translucent, transparent, and opaque?
Translucent
Allows some light to
pass through the
material. It’s not
possible to see through
translucent materials
Examples: frosty glass
Transparent:
Allows all or most light
to travel through. Its
possible to see clearly
through transparent
materials
Examples: Water, glass
Opaque:
Blocks all the light
passing through. Its
not possible to see
through opaque
material.
Examples: wood
Beams of light: Light travels in a straight line, however, light changes angel
when interacting with different materials.
What is the normal?
What is Reflection?
What is Refraction?
Refraction: Light changes speed as it crosses the boundary between one
substance and another substance. The change in speed causes the change
in angle.
When the material is a denser medium, for example from air to water/ glass,
it slows down and it bends towards the normal.
When light enters a less optically dense medium, for example from glass to
air or water to air, the light speeds up and its direction bend away from the
normal.
What is Dispersion?
Dispersion is the splitting of a white light through a glass prism.
The light would split into its spectrum of colours.