View
470
Download
9
Category
Tags:
Preview:
Citation preview
Dr Pusey
www.puseyscience.com
Q: What are the differences between a convex and concave mirror?
Recap - Convex & Concave Mirrors Concave – Dug out Like a Cave
Can form real and virtual images
Can focus light
Torches & Telescopes
Convex – Bulges out
Makes things appear smaller
Security mirrors
“objects in mirror are closer than they appear”
www.physicsclassroom.com
Recap
MIRROR
Show:• Angle of incidence• Angle of reflection• Normal• Reflected Ray• Incident Ray
Recap
MIRROR
Normal
Reflected RayIncident Ray
i r
Refraction Bending of light
Occurs when the light wave enters a different medium and changes speed
Light is the fastest in a vacuum (space)
Speed (vacuum) = 3x108 m/s
When light slows down, it bends TOWARDS the normal
Why is light refracted?The speed of light depends on the material through which the light is travelling. When light enters a different material (e.g. when moving from air into glass), the speed of light changes.
This causes the light to bend or refract.
The speed of light is affected by the density of the material through which it is travelling.
When light enters a more dense medium, its speed decreases and this is why refraction occurs.
air
glass
Your Turn As a wave enters a
medium where it travels slower, it bends towards the normal
As a wave enters a medium where it travels faster, it bends away from the normal
Faster speed
Slower speed
Normal
Normal
i
r
Your Turn
Glass
Show:• Angle of incidence• Angle of refraction• Normal• Refracted Ray• Incident Ray
Your Turn
Glass
Normal
i
r
Incident Ray
Refracted Ray
What happens when the ray leaves the glass block? Draw it!
Your Turn
Glass
Normal
Normal
i
r
i
r
Total Internal Reflection If the angle of incidence is large enough, light won’t
actually refract through to the next medium. It will instead reflect!
Diamonds
NBN Fibre Optics!
Lenses Transparent material that
direct/refocus light using the principles of refraction
Two types for you to learn:
Convex – Bulges on each side
Concave – Caves in on each side
https://en.wikipedia.org/wiki/Lens_%28optics%29
Convex Lens Focusses light (e.g. magnifying
glass)
The point at which light focusses is the “focal point”
https://en.wikipedia.org/wiki/Lens_%28optics%29
Concave Lens Spreads (diverges) the light
The point where the diverging light appears to come from is known as the “focal point”
https://en.wikipedia.org/wiki/Lens_%28optics%29
Your turn Finish these ray diagrams:
Your turn Finish these ray diagrams:
Focuses Light to the Retina to form an image
Changes the shape of the lens to focus on near and far objects
Contains light receptors.Where images areformed from light
Carries signals to the brain
Let’s light intothe eye!
Controls how much light is let into the eye
Refracts light into the lens for
focussingExtension!
The Eye
Recommended