Detecting light: cameras and the human eye
Select Lesson
Electricity
Waves
Forces and motion
Energy
Earth and atmosphere
Acids and alkalis
Chemical reactions
Pure and impure substances
The periodic table and properties of materials
Atoms, elements and compounds
States of matter
Genetics and evolution
Interactions and interdependencies
Plants
Human reproduction
Human gas exchange systems
Human nutrition, digestion and health
Human skeleton and muscles
Explainer Video
Summary
Detecting light: cameras and the human eye
In a nutshell
Light incident on a source can be absorbed and transferred into energy. Ray diagrams can be used to show how pinhole cameras and convex lenses focus light. Photo-sensitive materials absorb light and convert the energy into a chemical change or electrical impulse.
Focusing light
Pinhole cameras
A pinhole camera is a box with a tiny hole in one end and a translucent (semi-transparent) screen at the opposite end. Light enters the box through the pinhole. It's then focused onto the screen.
The light is focused so that it looks like it meets at a single point. If the light wasn't focused at the pinhole, the image would appear blurred on the screen.
 |
|
The image produced is upside-down, laterally inverted and smaller than the object.
Example
Pinhole cameras are used for photography as well as to observe eclipses.
Convex lenses
Using a convex lens is another way of focusing incoming light to a single point. This point is known as the lens' focal point. It is made from a transparent material which refracts light as it passes in and out of the lens.
 |
|
Example
If you wear glasses because you cannot see nearby objects (far-sightedness) then you'll be using a convex lens! They are also used for magnifying glasses and cameras.
Eyes
The eye is very important for focusing light in order to see. It works similarly to the convex lens, and focuses the light onto the focal point on the retina. The reason someone might need glasses is because their eye doesn't focus the light on the retina.
 |
|
Detecting light
Light waves carry energy which can be transferred to objects they come into contact with. This means that if a light ray hits a surface, it may transfer its energy to the surface. This process is called absorption.
Photo-sensitive materials detect light by absorbing light and converting the energy into a chemical change or an electrical impulse.
Example
Cameras focus light from an object onto photo-sensitive material by using a convex lens. The photo-sensitive material works by absorbing the light which transfers energy to the material. This causes a chemical change or, in modern day cameras, an electrical impulse.
Eyes also have photo-sensitive material in the retina. The retina is partly made up of cells that produce electrical impulses when they absorb light. These impulses are sent to your brain via the optic nerve.
FAQs - Frequently Asked Questions
What does the retina do?
The retina is partly made up of cells that produce electrical impulses when they absorb light. These impulses are sent to your brain via the optic nerve.
What is the point at which light is focused called?
The point at which light is focused is called the focal point.
How is light detected?
Photo-sensitive materials detect light by absorbing light and converting the energy into a chemical change or electrical impulse.