Physics Revision : Lenses

KEY POINTS ABOUT CONVEX (CONVERGING LENS):

• Refracts the light to focus it
• Used to magnify things
• Used in cameras
• It causes parallel rays of light to converge (move together) at the principal focus
• The princpial focus of a convex lens is where rays hitting the lens parallel to the axis all meet

KEY POINTS ABOUT CONCAVE (DIVERGING LENS):

• Spreads out light rays
• Used in torches
• Principle Axis - through the middle of the lens and light ray is not refracted as it hits the normal at 90°
• The principal focus of a diverging lens is the point where rays hitting the lens parallel to the axis appear to all come from - you can trace them back until they all appear to meet up at a point behind the lens