Refraction KEYWORDS : refraction, angle of incidenc Angle of refraction, refractive index Understand the phenomena of refraction ALL – Describe what happens during refraction MOST – Explain why refraction occurs SOME – State the relationship between the angle of incidence and Starter Refraction mind map
19
Embed
KEYWORDS: refraction, angle of incidence, Angle of refraction, refractive index KEYWORDS: refraction, angle of incidence, Angle of refraction, refractive.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Refraction
KEYWORDS: refraction, angle of incidence,Angle of refraction, refractive index
Understand the phenomena of
refractionALL – Describe what happens during refractionMOST – Explain why refraction occursSOME – State the relationship between the angle of incidence and the angle of refraction
StarterRefraction mind
map
Refraction
Refraction occurs when light moves between two mediums that have a different density. (The word medium just means ‘something that you can travel through’)
When light moves into a medium with a higher density, it slows down and will bend towards the normal. When it moves into a less dense medium, it speeds up and bends away from the normal.
LO: Understand the phenomena of refraction
Refractive Index
The refractive index of a material is a measure of how much light is refracted by it when it passes through the material. It can be calculated by using the equation:
Refractive index = Sin I / Sin R
LO: Understand the phenomena of refraction
I = angle of incidenceR = angle of refraction
Demonstration: Critical Angle
When performing refraction with a semi-circular block, an interesting phenomena is observed. When the light leaves the block, it bends away from the normal. This is expected as it is moving from a more dense to a less dense medium.
LO: Understand the phenomena of refraction
Demonstration: Critical Angle
As we continue to increase the angle of incidence, we reach a point where the refracted light seems to run across the top of the glass block! The angle at which this happens is called the ‘critical angle’
LO: Understand the phenomena of refraction
Demonstration: Critical Angle
If we increase the angle even more, we can see that the light ray is no longer refracted. Instead, it seems to reflect off inside of the straight edge of the semi-circular block. This is known as total internal reflection
We will explore this in greater detail later
LO: Understand the phenomena of refraction
Critical Angle
The critical angle of a material can be found using the following formula:
Refractive index = 1/sin(C)
LO: Understand the phenomena of refraction
Refractive index = property of a material C = Critical angle
Uses of Total Internal Reflection
Fibre optic cables are able to work using total internal
reflection. Light is sent through one end in short bursts and will
light up the other end.
These fibre optic cables are now used in high speed internet! They are now also used in
medicine…
LO: Understand how physics can be applied to medicine
KEYWORDS: converging, diverging, lenses, Focal point, virtual, real
Understand how to draw ray diagrams for
lenses
ALL – state the definition of converging and divergingMOST – Draw ray diagrams for lensesSOME – Explain when virtual and real images are formed when using lenses
Converging lensLO: understand how to draw ray diagrams for lenses
A converging lens is always convex. It makes rays that are coming in that are parallel converge onto a point. The point where the rays converge is called the principal focus, or focal point.Converging lenses are used in magnifying glasses and in cameras.
Real imageLO: understand how to draw ray diagrams for lenses
When an object is really far away from a converging lens, the light rays will be (almost) parallel when they reach the lens. The image that will be formed will be at the focal length.
Virtual imageLO: understand how to draw ray diagrams for lenses
A virtual image is formed by a converging lens if the object is nearer to the lens than the focal length. A diverging lens will ALWAYS form a virtual image. The image is always bigger than the object, the right way up and forms before the lens.