Seeing Things Through a Lens You See an Eye

Seeing Things Through a Lens What Does the Eye See?

Lens

Converging Lens Convex Lens Diverging Lens Concave Lens

The Parts of a Converging/Convex Lens O  Optical Centre F  Focus 2F  Focal Length

Convex Lens Characteristic Rays Any incident ray parallel to the principal axis will……

Any incident ray parallel to the principal axis will refract through the Focus. Convex Lens Characteristic Rays

Any incident ray passing through the Focus will…… Convex Lens Characteristic Rays

Any incident ray passing through the Focus will refract parallel to the principal axis. Convex Lens Characteristic Rays

Any incident ray passing through the Optical Centre will….. Convex Lens Characteristic Rays

Any incident ray passing through the Optical Centre will pass undeviated (straight through). Convex Lens Characteristic Rays

Any incident ray passing through the Optical Centre will pass undeviated (straight through). This will only happen if the lens is thin. The centre of the lens will the have little Lateral Displacement if it is thin.

Refraction occurs as the light rays enter and leave the lens.

If the lens is thin, we can simplify ray diagrams by assuming all refraction occurs at the centre of the lens. Thin lens have little Lateral Displacement.

Any incident ray passing through 2F will…… Convex Lens Characteristic Rays

Any incident ray passing through 2F will refract through 2F. Convex Lens Characteristic Rays

Predicting Images in a Convex Lens Any incident ray parallel to the principal axis will……

Predicting Images in a Convex Lens

Any incident ray parallel to the principal axis will refract through the Focus. Predicting Images in a Convex Lens

Any incident ray passing through the Focus will…… Predicting Images in a Convex Lens

Any incident ray passing through the Focus will reflect parallel to the principal axis. Predicting Images in a Convex Lens

Any incident ray passing through the Optical Centre will…… Predicting Images in a Convex Lens

Any incident ray passing through the Optical Centre will pass undeviated (straight through). Predicting Images in a Convex Lens

Where is the image? Predicting Images in a Convex Lens

The object is located where the rays appear to come from. Predicting Images in a Convex Lens

The image is also located where the rays appear to come from. Predicting Images in a Convex Lens

image's characteristics Smaller Inverted Between F & 2F Real image's characteristics Size Inversion Location Type

Your Turn Do the first two pages of L14 Predicting the Images of a Convex/Converging Lens Predicting Images in a Convex Lens You Tube Video Ray Tracing (Converging Lens) ) Further help is available at

ANSWERS FOLLOW FOR THE IMAGES ON 2nd PAGE of L14 Predicting the Images of a Convex/Converging Lens. Predicting Images in a Convex Lens

When the object is located at twice the focal length (2F)

Any incident ray parallel to the principal axis will…… When the object is located at twice the focal length (2F)

Any incident ray parallel to the principal axis will refract through the Focus. When the object is located at twice the focal length (2F)

Any incident ray passing through the Focus will…… When the object is located at twice the focal length (2F)

Any incident ray passing through the Focus will reflect parallel to the principal axis. When the object is located at twice the focal length (2F)

Any incident ray passing through the Optical Centre will…… When the object is located at twice the focal length (2F)

Any incident ray passing through the Optical Centre will pass undeviated (straight through). When the object is located at twice the focal length (2F)

image's characteristics Same Size Inverted At 2F Real When the object is located at twice the focal length (2F) image's characteristics Size Inversion Location Type

When the object is located between twice the focal length (2F) and the Focus (F)

Any incident ray parallel to the principal axis will…… When the object is located between twice the focal length (2F) and the Focus (F)

Any incident ray parallel to the principal axis will refract through the Focus. When the object is located between twice the focal length (2F) and the Focus (F)

Any incident ray passing through the Focus will…… When the object is located between twice the focal length (2F) and the Focus (F)

Any incident ray passing through the Focus will refract parallel to the principal axis. When the object is located between twice the focal length (2F) and the Focus (F)

Any incident ray passing through the Optical Centre will…… When the object is located between twice the focal length (2F) and the Focus (F)

Any incident ray passing through the Optical Centre will pass undeviated (straight through). When the object is located between twice the focal length (2F) and the Focus (F)

image's characteristics Larger Inverted Beyond 2F Real When the object is located between twice the focal length (2F) and the Focus (F)

When the object is located at the Focus (F)

Any incident ray parallel to the principal axis will…… When the object is located at the Focus (F)

Any incident ray parallel to the principal axis will refract through the Focus. When the object is located at the Focus (F)

Any incident ray passing through the Focus will…… When the object is located at the Focus (F)

Any incident ray passing through the Focus will travel parallel to the lens and not intersect it. When the object is located at the Focus (F)

Any incident ray passing through the Optical Centre will…… When the object is located at the Focus (F)

Any incident ray passing through the Optical Centre will pass undeviated (straight through). When the object is located at the Focus (F)

Where is the image? The rays appear to be parallel.

If the rays start on part of the object slightly closer to 2F, they are not parallel. They converge slightly, …… When the object is located at the Focus (F) Where is the image? The rays appear to be parallel.

When the object is located at the Focus (F) If the rays start on part of the object slightly closer to 2F, they are not parallel. They converge slightly, then they will meet far away. The Images Characteristics would be: Very Large Inverted Very Far Away (at ∞) Real

Where is the image? The rays appear to be parallel. When the object is located at the Focus (F)

If the rays start on part of the object slightly closer to O, they are not parallel. They diverge slightly, …… Where is the image? The rays appear to be parallel. When the object is located at the Focus (F)

If the rays start on part of the object slightly closer to O, they are not parallel. They diverge slightly, then they will meet far away in the opposite direction. The image's characteristics would be: Very Large Erect Very Far Away (at ∞) Virtual When the object is located at the Focus (F)

When the object is located between the Focus (F) and the Optical Centre (O)

Any incident ray parallel to the principal axis will…… When the object is located between the Focus (F) and the Optical Centre (O)

Any incident ray parallel to the principal axis will refract through the Focus. When the object is located between the Focus (F) and the Optical Centre (O)

Any incident ray moving in a direction that is the same as if it had passed through the Focus will…… When the object is located between the Focus (F) and the Optical Centre (O)

Any incident ray moving in a direction that is the same as if it had passed through the Focus will refract parallel to the principal axis.

Any incident ray passing through the Optical Centre will…… When the object is located between the Focus (F) and the Optical Centre (O)

any incident ray passing through the Optical Centre will pass undeviated (straight through). When the object is located between the Focus (F) and the Optical Centre (O),

Where is the image? The rays diverge. When the object is located between the Focus (F) and the Optical Centre (O)

If the rays diverge, the image is where they appear to meet in the opposite direction. Then the image's characteristics would be: Larger Erect Same Side as object Virtual When the object is located between the Focus (F) and the Optical Centre (O)

5)If the object IS MOVED far beyond twice the focal length (2F) of a CONVEX (CONVERGING) LENS, the image will move TOWARD the FOCUS. 6)If the object IS MOVED close toward the Focus of a CONVEX (CONVERGING) LENS, the image will move FAR BEYOND 2F. 7)In order to produce a VIRTUAL IMAGE with a CONVEX (CONVERGING) LENS, the object must be placed BETWEEN the FOCUS (F) AND the Optical Centre (O). 8)In order to produce a REAL IMAGE with a CONVEX (CONVERGING) LENS, the object must be placed BEYOND the FOCUS (F). Predicting Images in a Convex Lens

9)In order to produce an ERECT IMAGE with a CONVEX (CONVERGING) LENS, the object must be placed BETWEEN the FOCUS (F) AND the Optical Centre (O). 10)In order to produce the LARGEST IMAGE POSSIBLE with a CONVEX (CONVERGING) LENS, the object must be placed AT the FOCUS. 11) Why are only the red words flipped in the “WHAT A COOKIE” activity? Predicting Images in a Convex Lens

Now Try Concave Lens Do the rest of L14 Predicting the Images of a Convex/Converging Lens. You Tube Video Ray Tracing (Diverging Lens) ) Further help is available at

Concave Lens Characteristic Rays Any incident ray parallel to the principal axis will……

Any incident ray parallel to the principal axis will refract as if it had passed through the principal Focus. Concave Lens Characteristic Rays

Any incident ray moving toward the Secondary Focus will……

Concave Lens Characteristic Rays Any incident ray moving toward the Secondary Focus will refract parallel to the principal axis.

Concave Lens Characteristic Rays Any incident ray passing through the Optical Centre will……

Concave Lens Characteristic Rays Any incident ray passing through the Optical Centre will pass undeviated (straight through).

When the object is located beyond 2F

An incident ray parallel to the principal axis will…… When the object is located beyond 2F

An incident ray parallel to the principal axis will refract as if it had passed through the principal Focus.

When the object is located beyond 2F An incident ray moving toward the Secondary Focus will……

When the object is located beyond 2F An incident ray moving toward the Secondary Focus will refract parallel to the principal axis.

When the object is located beyond 2F An incident ray passing through the Optical Centre will……

When the object is located beyond 2F An incident ray passing through the Optical Centre will pass undeviated (straight through).

When the object is located beyond 2F Where is the image? The rays diverge.

When the object is located beyond 2F If the rays diverge, the image is where they appear to meet in the opposite direction. The image’s characteristics would be: Smaller Erect Same Side as Object Virtual

When the object is between 2F and F

An incident ray parallel to the principal axis will…… When the object is between 2F and F

An incident ray parallel to the principal axis will refract as if it had passed through the principal Focus.

When the object is between 2F and F An incident ray moving toward the Secondary Focus will

When the object is between 2F and F An incident ray moving toward the Secondary Focus will refract parallel to the principal axis.

When the object is between 2F and F An incident ray passing through the Optical Centre will……

When the object is between 2F and F An incident ray passing through the Optical Centre will pass undeviated (straight through).

When the object is between 2F and F Where is the image? The rays diverge.

When the object is between 2F and F If the rays diverge, the image is where they appear to meet in the opposite direction. The image’s characteristics would be Smaller Erect Same Side as Object Virtual

When the object is between F and O

An incident ray parallel to the principal axis will…… When the object is between F and O

An incident ray parallel to the principal axis will refract as if it had passed through the principal Focus.

When the object is between F and O An incident ray moving toward the Secondary Focus will……

When the object is between F and O An incident ray moving toward the Secondary Focus will refract parallel to the principal axis.

When the object is between F and O An incident ray passing through the Optical Centre will……

When the object is between F and O An incident ray passing through the Optical Centre will pass undeviated (straight through).

When the object is between F and O Where is the image? The rays diverge.

When the object is between F and O If the rays diverge, the image is where they appear to meet in the opposite direction. The image’s characteristics would be: Smaller Erect Same Side as Object Virtual

4)If the object IS MOVED far beyond twice the focal length (2F) of a CONCAVE (DIVERGING) LENS, the image will move TOWARD the FOCUS. 5)If the object IS MOVED close toward the Focus of a CONCAVE (DIVERGING) LENS, the image will move TOWARD the LENS. 6)In order to produce a VIRTUAL IMAGE with a CONCAVE (DIVERGING) LENS, the object can be placed ANYWHERE. 7)In order to produce a REAL IMAGE with a CONCAVE (DIVERGING) LENS, the object must be placed – IT CAN’T BE DONE. Predicting Images in a Concave Lens

8)In order to produce an ERECT IMAGE with a CONVEX (CONVERGING) LENS, the object can be placed ANYWHERE. 9)In order to produce the LARGEST IMAGE POSSIBLE with a CONVEX (CONVERGING) LENS, the object must be placed CLOSE TO THE LENS. Predicting Images in a Convex Lens