Thin Lenses & Mirrors

In the last lab we examined the laws of reflection and refraction which are fundamental to how mirrors and . Mirrors

reflect light so the real image side is on the same side as the object while lenses primary refract light making the real image side on that

opposite to where the object is located. Both mirrors and lenses come in two forms, converging with a positive focal length and diverging

with a negative focal point. A converging optic bends light rays towards each other while a diverging one bends them apart. Equations

in your text and in the Lenses & Mirrors Notes document in the previous module, can be used to find the relationships between the

object distance to the optic, the image distance to the optic, the object height, the image height, the image magnification and the focal

length of the optic.

1) If you were to find the focal point of a converging, or concave, mirror, it would be positive and half the radius of curvature. On

the diagram below draw the three principal reflected rays from the object (the arrow in this case which will indicate the position

(di), size (hi), orientation (upright or inverted), and nature (real or virtual) of the image formed. Label each value on the diagram

and give the actual numerical values according to the symbols used in equations from the Lenses & Mirrors Notes document.

(The three principal rays for reflection/mirrors are thoroughly described in your text.) do = 10cm f = 6cm

2) Open the phet Geometric Optics Mirror found here: https://phet.colorado.edu/sims/html/geometric-optics/latest/geometric-

optics_en.html. Use the simulation to verify or correct your answer to number (1) above. Then move around the object to determine if there is a location where it can be placed to result in a virtual image. If there is one, draw the location of both the

object and the image below. Add a ray diagram including the three principal rays.

3) Also using the simulation, describe what happens when the object is located at the near focal point. Explain what you are

observing below.

4) Using the same simulation, switch to the convex or diverging mirror. Move around the object to determine if there is a location

where it can be placed to result in a real image. Explain below why this is possible or not.

5) Lastly, for this simulation, move the object to the near focal point and draw the location of both the object and the image below.

Add a ray diagram including the three principal rays.

6) Next let us investigate the image formed by a converging, or convex, lens. On the diagram below draw the three principal

refracted rays from the object (the arrow in this case which will indicate the position (di), size (hi), orientation (upright or

inverted), and nature (real or virtual) of the image formed. Label each value on the diagram and give the actual numerical

values according to the symbols used in equations from the Lenses & Mirrors Notes document. (The three principal rays for

refraction/lenses are thoroughly described in your text.) do = 10cm f = 6cm

7) Now, switch to the phet Geometric Optics Lens found here: https://phet.colorado.edu/sims/html/geometric-

optics/latest/geometric-optics_en.html. Use the simulation to verify or correct your answer to number (6) above. Then move

around the object to determine if there is a location where it can be placed to result in an upright virtual image. Explain below

why this is possible or not.

8) Lastly let us do one exercise with a diverging lens which has a negative focal point. On the diagram below draw the at least two

principal refracted rays from the object (the arrow in this case which will indicate the position (di), size (hi), orientation (upright or inverted), and nature (real or virtual) of the image formed. Label each value on the diagram and give the actual numerical

values according to the symbols used in equations from the Lenses & Mirrors Notes document. (The three principal rays for

refraction/lenses are thoroughly described in your text.) do = 10cm f = -6cm

9) Using the same simulation, switch to the concave or diverging lens. Move around the object to determine if there is a location

where it can be placed to result in a real image. Explain below why this is possible or not.