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GCSE level Physics exam revision notes, types of
energy visible light & infrared
radiation energy transfer & examples explained
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Dr Phil Brown PhD:
Doc Brown's physics exam revision notes suitable for students of UK
IGCSE & GCSE level physics courses, ~ US grades 9-10 physics
[energy-0 page updated
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[KEY
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ENERGY INDEX: Types of
energy & energy stores, energy transfers & selected energy
calculations
(h) Light energy
This page will help you answer questions
such as ...
What is light energy? Can you store light energy?
Index of types of
energy stores/transfers
 Light
energy
(and a mention of infrared radiation)
(parts of the electromagnetic spectrum, like visible light, microwaves and infrared
etc.)
-
Strictly speaking light is NOT an energy
store, but an important form of energy and means of energy
transfer.
-
Light is an example of
electromagnetic radiation and the radiated energy is carried by particles with
wave-like properties called photons.
-
All luminous
sources by definition give out visible light eg the sun, light bulb, candle, fire
etc.
-
When light
impacts on any material, the energy is absorbed eg sunlight shining on plant
leaves in photosynthesis, light falling on the retina of our eyes.
-
You cannot store light energy because
ultimately it is always absorbed by materials it impact on and converted
into another type of energy e.g. heat.
-
Note that invisible infrared radiation is
converted directly into thermal (heat) energy when absorbed by a surface eg warmth feeling in sunlight, standing by a
fire, a toaster.
-
Solar cells can convert light energy
directly into electrical energy which can be used as it is produced or
stored in a rechargeable battery system.
-
Digital cameras produce an
image
-
See
Electromagnetic radiation,
types, properties and uses
-
Introduction to heat transfer -
including infrared radiation
Extended
Key points for Physics -
energy transfers
involving visible light and infrared radiation
Information
sources for Doc Brown's key points: IGCSE-GCSE physics are based on textbooks
& syllabus-specifications for students taking the UK AQA,
Edexcel, OCR 21st Century Science, OCR Gateway science suite, WJEC, CCEA &
CIE GCSE
physics 9-1 level science examinations.
Here's a detailed,
syllabus-aligned revision guide on Visible Light Energy,
tailored for GCSE/IGCSE Physics students across WJEC, CCEA, CIE, AQA, Edexcel, and OCR exam boards:
Visible Light Energy – GCSE Physics Revision
Notes
What is Visible Light?
- Visible light
is the part of the electromagnetic spectrum that can be
detected by the human eye.
- It consists of transverse waves
with wavelengths between ~400 nm (violet) and ~700
nm (red).
- It travels at the speed of light
in a vacuum: c = 3.0 x 108 m/s)
- It transfers energy from
a source (like the Sun or a bulb) to an absorber (like your skin or a solar
panel).
Colours of Visible Light
| Colour |
Wavelength (nm) |
Frequency (Hz) |
Energy |
| Red |
~700 |
Lowest |
Lowest |
| Orange |
~620 |
|
|
| Yellow |
~580 |
|
|
| Green |
~530 |
|
|
| Blue |
~470 |
|
|
| Indigo |
~440 |
|
|
| Violet |
~400 |
Highest |
Highest |
Mnemonic:
Richard Of York Gave Battle In Vain (ROYGBIV)
I always taught a phonetic:
vibgyor (vib-guy-or)
Properties of Visible Light
- Transverse wave:
Oscillations are perpendicular to direction of energy transfer.
- Can be reflected,
refracted, absorbed, or transmitted.
- Undergoes dispersion:
white light splits into colours through a prism.
- Carries energy:
can cause heating, chemical changes, or generate electricity.
Energy Transfers Involving Visible Light
| Scenario |
Energy Transfer Pathway |
| Sunlight warming skin |
Light (radiation) → Thermal (skin) |
| Solar panels |
Light → Electrical (via photovoltaic
cells) |
| Photosynthesis in plants |
Light → Chemical (glucose in plants) |
| Torch bulb |
Chemical (battery) → Electrical →
Light + Thermal |
| Laser pointer |
Electrical → Light |
Real-World Uses of Visible Light
| Application |
Description |
| Vision |
Light reflects off objects and enters
our eyes |
| Photography & Cameras |
Light is focused onto sensors or film
to capture images |
| Fibre optics |
Light signals travel through cables
via total internal reflection |
| Communication |
Visible light used in Li-Fi
(Light Fidelity) for wireless data transfer |
| Safety & Illumination |
Traffic lights, headlights, torches,
etc. |
| Medical imaging |
Endoscopes use visible light to view
inside the body |
Exam Tips for All Boards
Use correct terminology
- Say “energy is transferred by radiation”
not “light energy is made.”
Understand wave behaviour (see
waves and optics pages)
- Know how light behaves at boundaries:
reflection, refraction, absorption,
transmission.
Draw ray diagrams (see
waves and optics pages)
- Show incident and reflected/refracted rays
with correct angles and normals.
Know the electromagnetic spectrum
- Visible light is between infrared
and ultraviolet.
Practice with colour filters (see
waves and optics pages)
- Understand how filters absorb and transmit
specific wavelengths.
Link to energy stores
- Light transfers energy from a
source (e.g. bulb, Sun) to a store (e.g. thermal,
chemical).
Worked Example of solar panel conversion of
light energy to electrical energy
Q:
A solar panel receives 500 J of light energy and converts 120 J into electrical
energy.
What is the efficiency of the solar panel?
A:
Efficiency = (120 / 500) x 100 =
24%
Keywords, phrases and learning objectives
on light energy transfer
Know that light waves (photons) are a form of energy
which can be transferred from one place to another.
Know that light can be converted into electrical
energy using solar cells.
WHERE
NEXT?
Specific notes on types of energy and energy stores and
associated calculations
FULL INDEX of
Types of energy & stores - examples compared/explained, calculations of
mechanical work done & power notes
All my ENERGY notes
ALL my Physics Notes
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physics,
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when studying GCSE level physics, What is significant about light
energy, describing the theory of light energy when studying GCSE
level physics, revision notes for light energy in exams, online exam
help for light energy, revision notes about light energy, what do I need
to learn about light energy for by GCSE physics exam?
help to understand the light energy topic in preparation for GCSE physics exam
question, how to
prepare for questions involving light energy in a GCSE physics examination?
Revision notes on light energy based on the syllabus-specifications
for students taking IGCSE/GCSE level physics examinations, summary
revision notes and key points on light energy for students taking the AQA
igcse/gcse physics notes on light energy, Edexcel gcse
physics notes on light energy, OCR 21st century GCSE
physics notes on light energy, OCR gateway
GCSE physics notes on light energy, WJEC gcse physics notes on light
energy, CCEA
gcse physics notes on light energy for students taking CIE Cambridge igcse
physics, exam revision notes on
light energy, useful for US grade 9-10 physics courses
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INDEX ENERGY: Types, stores, transfers, energy
calculations |
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