Post on 17-Dec-2015
transcript
Convex Mirrors
Virtual Images
Review
• For any position where an object is in front of a Concave Mirror past the focal point, the rays of light converge, forming a real image
C F
Real, inverted image of the pencil.
Review
• An object on F will disapear.
• But if it goes past f it shows up again…
C F
Virtual Images in Concave Mirrors
• If the object is in front of the focal point, the rays of light diverge after hitting the mirror.
C F
Virtual Images in Concave Mirrors
• Note: This arrow lines up with the focal point… Everything else is like before. Almost.
C F
Virtual Images in Concave Mirrors
• When do the red lines cross? So how do we see a reflection?
C F
Virtual Images in Concave Mirrors
• Extend the red lines to the OTHER side of the mirror. (Inside the mirror and wall)
C F
Virtual Images in Concave Mirrors
• This is where you EYE SEES the image:
C F
RealPencil Image
Virtual Images in Concave Mirrors
• Since it’s on the OTHER side of the mirror, it’s a VIRTUAL image.
C F
RealPencil Image
Real vs Virtual Image
C F
RealPencil
Images on the same side of the mirror as the
object: REAL IMAGES
Images on the other side of the mirror (in the wall):
VIRTUAL IMAGES
Convex Mirrors
• Convex Mirrors are also called diverging mirrors. Light rays never intersect once they hit the mirror.
F C
The focal point and center of curvature still exist, they are just on the OTHER side of the mirror now.
Convex Mirrors
• We can use the same trick as before to make the Laws of Mirrors work.
F C
Law #1
• We can use the same trick as before to make the Laws of Mirrors work.
F C
Law #1
• We can use the same trick as before to make the Laws of Mirrors work.
F C
Law #2
• Law 2 starts out going toward the focal point.
F C
Law #2
• Then bounces back parallel. (Remember to use the trick)
F C
Example
• Let’s put the two together.
F C
Example
• Law 1:
F C
Example
• Law 2:
F C
Example
• Law 2:
F C
A Note on Focal Points
• For Convex Mirrors, since the focal point is on the opposite side of the mirror from the object, the value given will be negative.
• Example: A focal point of -9 cm indicates the point F is 9 cm from the mirror on the opposite side of the actual object
F
9 cm
Magnification and Convex Mirrors
• As an object gets farther away from a Convex Mirror, the image gets smaller and smaller.
• As the object gets closer, the object gets nearer to the actual size of the object.
Object vs. Virtual Image