the new stuff relies on you understanding the physics from P1 - please get back to me with questions about that
Lenses rely on a good understanding of REFRACTION - so - here goes
REFRACTION HAPPENS WHEN LIGHT CHANGES SPEED AT A BOUNDARY
the best diagram in the world shows this
Light is refracted through a glass block like this :
can you compare the car diagram with the glass block diagram?
the angles involved in REFRACTION are governed by SNELL'S LAW
- the refactive index (n) is a constant that is a property of transparent materials
n = sin i / sin r
if glass blocks are shaped in a certain way, they will bring light to a focus - the shape is called CONVEX and the distance between the middle of the lens and the focal point is called the FOCAL LENGTH (you can find this number on the side of camera lenses)
Convex lenses can be used as cameras, projectors or magnifying glasses - the first two produce images that are REAL (an image that forms on a screen) but a magnifying glass forms an image that is VIRTUAL (that needs to be seen by someone's eyes).
we will learn how to construct these diagrams next lesson
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