OPTICS Refraction in Lenses

Types of Lenses Convex (Converging Lens) Concave (Diverging Lens) Makes parallel rays converge towards each other Concave (Diverging Lens) Makes parallel rays diverge away from each other

Types of Lenses Applications of Convex Lenses Magnifying Glass Glasses

Types of Lenses Applications of Concave Lenses Flashlights Headlights

Points of Interest (Convex Lens) FRONT OF LENS BACK OF LENS Object Principal Axis Secondary Focus Primary Focus

Points of Interest (Concave Lens) FRONT OF LENS BACK OF LENS Object Principal Axis Primary Focus Secondary Focus

Finding an Image (Convex Lens) FRONT OF LENS BACK OF LENS O P.A. F F’

Finding an Image (Convex Lens) LINE 1 Draw a straight line from the top of the object straight to the lens (parallel to the principal axis). Then, from that point in the lens, refract the light ray through the lens, through the primary focus (F’).

Finding an Image (Convex Lens) FRONT OF LENS BACK OF LENS O P.A. F F’ LINE 1

Finding an Image (Convex Lens) LINE 2 Draw a second line from the top of the object, through the secondary focus (F) to the lens. Then, refract the light ray straight through the lens, parallel to the principal axis

Finding an Image (Convex Lens) FRONT OF LENS BACK OF LENS O P.A. F F’ LINE 2 LINE 1

Finding an Image (Convex Lens) LINE 3 Draw a third line from the top of the object, straight through the optical centre.

Finding an Image (Convex Lens) FRONT OF LENS BACK OF LENS O P.A. F F’ LINE 2 LINE 3 LINE 1

Finding an Image (Convex Lens) Finally, the top of the image is located at the intersection point of your light rays after they refract through the lens. Note: You only need 2 of the 3 lines to locate an image.

Finding an Image (Convex Lens) FRONT OF LENS BACK OF LENS O P.A. F F’ LINE 2 IMAGE LINE 3 LINE 1

Describing an Image To describe an image use SALT S - Size (Bigger or Smaller than Object) A - Attitude (Upright or Inverted) L - Location (In Front or Behind Lens) T - Type (Real or Virtual) * Note, Real images are Behind the lens.

Finding an Image (Convex Lens) FRONT OF LENS BACK OF LENS O P.A. F F’ LINE 2 IMAGE LINE 3 S – Same A – Inverted L – Behind Lens T – Real Image LINE 1

Finding an Image (Concave Lens) FRONT OF LENS BACK OF LENS O P.A. F’ F

Finding an Image (Concave Lens) LINE 1 Draw a straight line from the top of the object straight to the lens (parallel to the principal axis) Then, from that point in the lens, refract the light ray through the lens, in line with the primary focus (F’). Then, extend the refracted ray into the virtual space in front of the lens.

Finding an Image (Concave Lens) BACK OF LENS FRONT OF LENS O P.A. F’ F LINE 1

Finding an Image (Concave Lens) LINE 2 Draw a straight line from the top of the object towards the secondary focus (F). Then, from that point in the lens, refract the light ray through the lens, parallel to the principal axis. Then, extend the refracted ray into the virtual space in front of the lens

Finding an Image (Concave Lens) BACK OF LENS FRONT OF LENS O LINE 2 P.A. F’ F LINE 1

Finding an Image (Convex Mirror) Finally, the top of the image is located at the intersection point of your light rays after they have been extended into the virtual area.

Finding an Image (Concave Lens) BACK OF LENS FRONT OF LENS O LINE 2 P.A. F’ F IMAGE LINE 1

Describing an Image To describe an image use SALT S - Size (Bigger or Smaller than Object) A - Attitude (Upright or Inverted) L - Location (In Front or Behind Lens) T - Type (Real or Virtual) * Note, Virtual images are In Front of the lens.

Finding an Image (Concave Lens) BACK OF LENS FRONT OF LENS O LINE 2 P.A. F’ F IMAGE LINE 1 S – Smaller A – Upright L – In Front of Lens T – Virtual Image