Thin LensesBy: Olivia and Noelia

Objectives: (Thin Lenses 14.2)

• Compare diverging and converging lenses

• Relate concepts to eyeglasses and contact lenses

• Describe the positioning of lenses in compound microscopes and telescopes

Introduction

Hey ya’ll, today we will be covering lesson 14, section 2 over Thin Lenses. Hopefully by the end of this lesson, you will better understand…

• Thin Lenses

• Diverging and converging lenses

• Ray diagrams

Introduction Continued...

Hopefully ya’ll will also better understand…

• What type of lenses are used for the correction of nearsightedness and farsightedness

• How lenses are positioned in compound microscopes and telescopes

Information

• Lenses use refraction, unlike mirrors that use reflection.

• Refraction is simply the bending of light as it passes from one substance to another.

• A lens forms an image by bending rays of light that pass through it.

Diverging Lenses

• Also known as concave lens

• These lens are thinner in the middle, causing the rays of light to appear to come from a single point

• After light is passed through these lenses, it bends and splits (diverges)

Diverging Lenses Continued...

Converging Lenses

• Also known as convex lens

• These lenses are thicker in the middle, causing rays of light that are initially parallel to meet at a single point called the focal point

• After light is passed through these lenses, it bends and comes together at one point (focal point)

Converging Lenses Continued...

Ray Diagrams

Nearsightedness Correction

o When the eye is too long.

o The focus point is in front of the retina, instead of sharply being focused in.

Nearsightedness Correction

• To correct this problem diverging lenses are used.

Farsightedness Correction

• When the eye is too short, and the focus point is behind the retina

Farsightedness Correction

• To correct this problem converging lenses are used

Compound Telescopes

• A telescope is an instrument made to make distant objects appear nearer.

• It contains an arrangement of lenses, by which rays of light are collected

and focused and the resulting image magnified.

Compound Microscopes

• A microscope is an instrument that is used for viewing very small objects, such as animal or plant cells, which are typically magnified several hundred times.

• A microscope has

two main lenses

(ocular and objective)

Questions

1) What is another name for diverging lenses?

• Concave

2) How many lenses does a microscope have? What are they called?

• Two (ocular and objective)

3) What kind of lens are used to correct farsightedness?

• Converging

Questions Continued...

4) Where is the focus point located on a near-sighted person’s eye?

• In front of the retina

5) In order for a compound telescope to produce an image, what kind of lenses must be present?

• Converging

Questions Continued...

6) Which lenses makes light disperse after being bent and passed through?

• Diverging

7) True/False...Farsightedness people’s focus point is located behind the retina?

• True

8) Which instrument is designed to make distant objects appear nearer?

• A telescope

Work Sitedstaff, M. (2012, March 3). Definition. Mayo Clinic. Retrieved October 29, 2013, from

http://www.mayoclinic.com/health/nearsightedness/DS00528

staff, M. (2012, April 24). Definition. Mayo Clinic. Retrieved October 29, 2013, from http://www.mayoclinic.com/health/farsightedness/DS00527

Diverging Lenses - Ray Diagrams. (n.d.). Diverging Lenses - Ray Diagrams. Retrieved October 29, 2013, from http://www.physicsclassroom.com/Class/refrn/U14l5ea.cfm

Converging Lenses - Object-Image Relations. (n.d.). Converging Lenses - Object-Image Relations. Retrieved October 29, 2013, from http://www.physicsclassroom.com/Class/refrn/u14l5db.cfm

How a Compound Light Microscope Works. (n.d.). Compound Light Microscope: How It Works. Retrieved October 29, 2013, from http://www.indepthinfo.com/microscopes/compound.htm

Hewitt, P. (2009). Lenses. Conceptual Physics The High School Program (pp. 602 - 616). Upper Saddle River : Pearson Education .