MOD 5  LECTURE  7                          LENSES

In this lecture you will learn:

TYPES OF LENSES - CONVEX
CONVEX LENSES: notice that lenses dont need to be convex on both sides

The most obvious use of refraction is for lenses, which help people who have vision problems

Lenses are essential for microscopes and telescopes.

convex lenses are also known as A.K.A. converging lenses.
 
 

Rays that enter the lens converge (bend) toward the mid line of the lens and then come to a point called the focus or focal point and form an image.
 
 

The easiest way to find the FOCAL POINT is to hold the lens over paper under the sun's rays. When the lens is held at the focal length, the paper will begin to burn. (sun is at infinite distance)

1. Image is upside down and switched Left to Right.

2. The image is real (can be projected onto a screen)

3. The focal length is the distance from the middle of the lens
to the formed image (focal point).

4. only the outer curve is essential. So the rest of   the lens
can be removed to lighten the weight of glasses and reason 
why contact lenses are possible

This is a convex lens. 

Notice the image of the buildings are both upside down and switched left to right. 

1. Image is upside down and switched Left to Right.

2. The image is real (can be projected onto a screen).

3. The image is smaller

This is also a convex lens, a magnifying lens. However, the image is formed inside the focal length when held close to an object or print and as a result:

1 a diverging image is produced
2 the image is right side up and not switched left to right
3 the image is magnified
4 the image is virtual

Both glasses and contact lenses are inside the focal point so they dont switch the image upside down or flip them left to right. 
 


 
TYPES OF LENSES - CONCAVE
Concave lenses A.K.A. diverging lenses.                                                                       
 
 
Light that enters diverges or spreads as it exits the other side of the lens.

1- Images are right side up and correct left and right.
2- Images are virtual.
3- focal point is where it appears that the rays of light come from.

CONCAVE LENSES are used to correct for nearsightedness

Concave lens showing image is right side up and correct left to right. 

 
TYPES OF MIRRORS: CONVEX
CONVEX MIRRORS:

ALL mirrors are virtual, right side up, but flipped right to left
Convex mirrors have images that are smaller and closer than they appear.

 

Images appear smaller AND further away, like mirrors on the right side of cars and mirrors placed on corners to help people see who is coming around the corner
Mirrored spheres or globes used as decoration in gardens, or, to chase off birds when they see movement in the mirror..
 
 

smaller, smaller, smaller, thru the looking glass.... 


 
TYPES OF MIRRORS: CONCAVE
CONCAVE MIRRORS:

Form a virtual, right side up image but flipped image
 

 

The image is enlarged

SHAVING OR MAKEUP MIRRORS


 
SUMMARY OF LENSES AND MIRRORS
image size side up switched
convex lens real smaller upside down yes
convex lens of the eye real smaller upside down yes
convex magnifying lens virtual larger right side up no
concave lens virtual smaller right side up no
convex mirror virtual smaller right side up yes
concave mirror virtual larger right side up yes
magnifying glass        
right side mirrors on cars        
mirrored spheres        
shaving or makeup mirrors