Bending That Light

Today was all about lenses and image formation and groups endured either the math involved with predicting image properties or using ray diagrams to analyze image formation by lenses.

B, E and F Blocks took their first steps with lenses today (well, E and F Blocks do have some lab experience in this area). The characteristics of converging and diverging lenses were examined and their abilities form images was explored. We spent time working through the construction of a ray diagram for a converging lens making a real image and folks have some more of these to do for homework. B and E Blocks also have a virtual image to deal with, so don't forget that you have a nice textbook to help you with that (might check page 571), but F Block only has to worry about real image formation. We'll look over these tomorrow before moving on to using the thin-lens formula and magnification formulas to more precisely hammer down numbers for image position and size.

C Block reviewed their ray diagrams and used those diagrams as examples to help clarify the relationship between object position and type/size of image formed for converging lenses. As you move the object towards the lens, the real image formed grows in size and moves away from the lens (q and M increase). At the focal point, the image forms at infinity and if you continue to push the object forward, the image now becomes virtual, with image distance and magnification increasing as you progressively approach the lens. We then started working on the math involved with lenses to put some precise values for our image properties and your homework tonight will give you additional practice working with the thin-lens and magnification formulas. We'll go over this and the 15.1 homework tomorrow before starting your lab on lenses.