lens/focal length picture

[Tracy Greeley-Adams]

I did a word document of the picture in the book to help in my class.  I have used this in a powerpoint as well as taking the candle out and have the students draw this at the conclusion of the activity.  feel free to use/ change etc.

[Eisenkraft]

I did a word document of the picture in the book to help in my class.  I have used this in a powerpoint as well as taking the candle out and have the students draw this at the conclusion of the activity.  feel free to use/ change etc.

Tracy,  nice idea, but some of the physics is wrong.  When trying to make ray diagrams, you must make the lens very thin for them to be accurate (a vertical line would work well.)  Also, you need a second ray from the top of the object that goes through the center of the lens to see where the image would appear.  With your diagram, you can place the image anywhere while we know it should only be in one position.

Hope this helps.

Arthur

[Matt Anthes-Washburn]

I have a question. In FYTD #3, the text states that when the object is very far away, the image distance is about equal to the focal length of the lens. I believe we said the same thing about convex mirrors. I'm confused, however, as to what the ray diagram would look like there. How do the rays converge at the focal point and somehow manage to spread back out to make a 10 cm-tall image, taking essentially no distance to do it? I know the rays do go through the focal point because the image is inverted.

What does this ray diagram look like?

[Sushma Sharma]

I have a question. In FYTD #3, the text states that when the object is very far away, the image distance is about equal to the focal length of the lens. I believe we said the same thing about convex mirrors. I'm confused, however, as to what the ray diagram would look like there. How do the rays converge at the focal point and somehow manage to spread back out to make a 10 cm-tall image, taking essentially no distance to do it? I know the rays do go through the focal point because the image is inverted.

What does this ray diagram look like?

I have not done this activity as yet,but  planning to explain them using this diagram. Considering the object is far off, most of  light rays raching the lense will be almost parallel  even though they are inclined to the  principal axis as they pass through the focus before entering the double lens.