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# Light

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by

## Sarah McLean

on 5 September 2013

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#### Transcript of Light

Light
This prezi is about light. Topics covered include Sources of Light, Mirrors and Lenses.
Sources of light
Objects that create light are luminous
A beam of light is composed of a group of rays travelling together
Rays of light travel in straight lines
Rays of light rebound off an object and enter our eyes, forming an image on our retina. This is how we see things.
Lenses
'Real Image' refers to an image formed on a screen where rays of light intersect. The 'real image' is upside down or inverted.
The 'Virtual Image' refers to an image which can only be viewed through a lens. It is the right way up and magnified.
Mirr rs
When a ray of light hits a shiny surface, reflection occurs
An imaginary line called the 'normal' is used to measure the angle of incidence and angle of reflection
The angle of incidence and the angle of reflection are always equal
This is an example of refraction.
Concave mirrors
Concave mirrors cave inwards
When rays of light hit a concave mirror they are reflected inwards
Also known as converging mirrors
Concave mirrors reflect parallel rays inwards
How an image forms
Light rays reflect off a mirror and then enter your eyes
Your brain thinks the light has come along a straight trail because light travels in straight lines
The image forms from where the light appears to have come
Light is scattered in all directions from a rough surface, therefore the rays don't appear to have a single source. This means there is no reflected image
Plane Mirrors
Plane mirrors are flat
The image appears to come from the point where the light is reflected
The image is the same distance from the mirror as the object
Convex Mirrors
Convex mirrors curve outwards
When rays of light hit a convex mirror they are reflected outwards
Also called diverging mirrors
Convex mirrors spread parallel rays outwards after reflection
Refraction
Refraction is the bending of light as it travels from one material to another
Refraction only occurs when the material is hit by light at an edge
As the light travels from more to less dense, it increases in speed and moves away from the normal
As the light travels from less to more dense, it decreases in speed and moves towards the normal
Convex Lenses
Convex lenses are also known as converging lenses
They focus rays of light at a point called 'the focus'
'The focal length' refers to the distance in which the lens is to the focus
Parallel rays come to a focus after passing through a convex lens
Concave Lenses
Concave lenses are also known as diverging lenses
They produce images which are smaller, upright and virtual
The diverging rays appear to have come from the focus
By Sarah McLean
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