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					Which ray is NOT correct?




            p.a.
                        R   f
       1)

            2)
                   3)
       Which ray is NOT correct?
Ray through center should reflect back on self.




                       p.a.
                                   R   f
                  1)



                              3)
Cases for Concave Mirrors
           CONCAVE MIRROR: OBJECT BEYOND C

           Image type:   REAL VIRTUAL NO IMAGE

           Image location:      BETWEEN F & V
                                BETWEEN F & C
                                AT C
                                BEYOND C
                                BEHIND MIRROR

           Image size:   SAME ENLARGED REDUCED

           Image orientation:   ERECT   INVERTED
Cases for Concave Mirrors
           CONCAVE MIRROR: OBJECT BEYOND C

           Image type:   REAL VIRTUAL NO IMAGE

           Image location:      BETWEEN F & V
                                BETWEEN F & C
                                AT C
                                BEYOND C
                                BEHIND MIRROR

           Image size:   SAME ENLARGED REDUCED

           Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT AT C

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT AT C

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT BETWEEN C & F

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT BETWEEN C & F

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT AT F

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT AT F

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT BETWEEN V & F

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONCAVE MIRROR: OBJECT BETWEEN V & F

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
                    Mirror Equation
                                                                do
            1 1 1
                                                      O
            do di f                                                   f
                                                            c
• do = distance object is from mirror:
      Positive: object in front of mirror                       I
      Negative: object behind mirror
                                                                     di
• di = distance image is from mirror:
      • Positive: inverted image (in front of mirror)
      • Negative: upright image (behind mirror)
• f = focal length mirror:
      • Positive: concave mirror
      • Negative: convex mirror (coming soon)
The image produced by a concave mirror of a
 real object is:
    1) Always Real
    2) Always Virtual
    3) Sometimes Real, Sometimes Virtual
Concave mirror: f > 0
Real Object means in front of mirror: do > 0
    Mirror Equation:
         1 1 1                1 1 1
                               
         do di f              di f d0
 di can be negative or positive!
                Concave Mirror
   Where in front of a concave mirror should you
    place an object so that the image is virtual?
                                      Mirror Equation:
1) Close to mirror
                                            1 1 1
2) Far from mirror                             
                                            do di f
3) Either close or far
4) Not Possible                             1 1 1
                                               
                                            di f d0
• Concave mirror: f > 0
• Object in front of mirror: do > 0
• Virtual image means behind mirror: di < 0
• When do < f then di <0 : virtual image.
           Magnification Equation
         hi  di                                                         do
       m 
         ho  do                                          O

• ho = height of object:                                            
      • Positive:   always                                                  

• hi = height of image:
                                                                        I
      • Positive: image is upright
      • Negative: image is inverted
                                              Angle of incidence
• m = magnification:                                                            di
      • Positive / Negative: same as for hi    ho
      • < 1: image is reduced                                  
      • > 1: image is enlarged                                     do
                                                        di
                             ho hi
                    tan( )       hi              
                                                             Angle of reflection
                             d o di
           Solving Equations
A candle is placed 6 cm in front of a concave mirror with
  focal length f=2 cm. Determine the image location.




Compared to the candle,
the image will be:
                               p.a.

    • Larger
                                         R       f




    • Smaller
    • Same Size
           Solving Equations
A candle is placed 6 cm in front of a concave mirror with
  focal length f=2 cm. Determine the image location.

    1  1    1          di = + 3 cm (in front of mirror)
       
  6 cm di 2 cm                  Real Image!




Compared to the candle,
the image will be:
                                p.a.

    • Larger
                                           R        f




    • Smaller
    • Same Size
               Magnification
A 4 inch arrow pointing down is placed in front of a mirror
  that creates an image with a magnification of –2.

What is the size of the image?                  4 inches

1) 2 inches
2) 4 inches
3) 8 inches



What direction will the image arrow point?
1) Up                    2) Down
               Magnification
A 4 inch arrow pointing down is placed in front of a mirror
  that creates an image with a magnification of –2.

What is the size of the image?       hi
                                  m
                                                4 inches

1) 2 inches                          ho
2) 4 inches
3) 8 inches
                              Magnitude gives us
                              size.
                                      hi  mh0  2 4
What direction will the image arrow point?
1) Up                     2) Down (-) sign tells us it’s
                                    inverted from object
           Convex Mirror Rays
   1) Parallel to principal axis reflects ______________.
   2) Through f, reflects ______________________.
   3) Through center.                        Complete the rays!


                   O        #1

                       #2        #3


                                                      c
                                       f
Image is:
  Virtual    or    Real
  Upright    or    Inverted
  Reduced or       Enlarged
(always true for convex mirrors!)
           Convex Mirror Rays
   1) Parallel to principal axis reflects through f.
   2) Through f, reflects parallel to principal axis.
   3) Through center.
                             #1
                   O
                       #2         #3        I

                                        f               c
Image is:
  Virtual (light rays don’t really cross)
  Upright (same direction as object)
  Reduced (smaller than object)
(always true for convex mirrors!):
CONVEX MIRROR

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
CONVEX MIRROR

Image type:   REAL VIRTUAL NO IMAGE

Image location:      BETWEEN F & V
                     BETWEEN F & C
                     AT C
                     BEYOND C
                     BEHIND MIRROR

Image size:   SAME ENLARGED REDUCED

Image orientation:   ERECT   INVERTED
             Solving Equations
A candle is placed 6 cm in front of a convex mirror with
focal length f=-3 cm. Determine the image location.




Determine the magnification of the candle.




If the candle is 9 cm tall, how tall does the image candle
appear to be?
             Solving Equations
A candle is placed 6 cm in front of a convex mirror with
focal length f=-3 cm. Determine the image location.
    1  1     1            di = - 2 cm (behind mirror)
       
  6 cm di  3 cm                     Virtual Image!

Determine the magnification of the candle.
      di    - 2 cm
  m                m = + 1/3
      do     6 cm
If the candle is 9 cm tall, how tall does the image candle
appear to be?

               hi      hi = + 3 cm
     1/ 3 
             9 cm              Image is Upright!
  Where should you place an object in front of
   a convex mirror to produce a real image?
1) Object close to mirror
2) Object far from mirror
3) Either close or far
4) You can’t
   Where should you place an object in front of
    a convex mirror to produce a real image?
                                         Mirror Equation:
1) Object close to mirror
                                              1 1 1
2) Object far from mirror                        
                                              do di f
3) Either close or far
4) You can’t
                                                  1 1 1
                                                     
• Convex mirror: f < 0                            di f d0
• Object in front of mirror: do > 0   di is
                                      negative!               do is
• Real image means di > 0                                     positive
                                                   f is
                                                   negative
           Mirror Summary
• Angle of incidence = Angle of Reflection
• Principal Rays
    – Parallel to P.A.: Reflects through focus
    – Through focus: Reflects parallel to P.A.
    – Through center: Reflects back on self
• |f| = R/2
• 1 1 1
       
  do di f
•      hi    di
    m    
       ho    do
   Light Doesn’t Just Bounce
        It Also Refracts!
Reflected: Bounces (Mirrors!)
                          i = r
        i r
                             1 1 1
                                
                             d0 di f

Refracted: Bends (Lenses!)
        1        n1
                       n1 sin(1)= n2 sin(2)
                  n2
             2
         Index of Refraction
             186,000 miles/second: it’s not
             just a good idea, it’s the law!

                                 Speed of
                         c       light in
                      v         vacuum
                         n
Speed of light in
medium
                                Index of refraction


    vc             so        n 1
                    always!
                 Snell’s Law
When light travels from one medium to another the
speed changes v=c/n and the light bends


             n1 sin(1)= n2 sin(2)


                     n1
       1
                            1) n1 > n2
            2       n2
                            2) n1 = n2
 Compare n1 to n2.          3) n1 < n2
        Snell’s Law Practice
Usually, there is both reflection and refraction!

A ray of light traveling through the air (n=1) is incident
on water (n=1.33). Part of the beam is reflected at an
angle r = 60. The other part of the beam is refracted.
What is 2?

                  1             r
        n1

        n2
                                      n1 sin 1  n2 sin 2
                    normal




                                2
        Snell’s Law Practice
Usually, there is both reflection and refraction!

A ray of light traveling through the air (n=1) is incident
on water (n=1.33). Part of the beam is reflected at an
angle r = 60. The other part of the beam is refracted.
What is 2?
                                     1 =r =60
                   1     r         sin(60) = 1.33 sin(2)
        n1                              2 = 40.6 degrees

        n2
                                     n1 sin 1  n2 sin 2
                    normal




                                2

				
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posted:10/23/2012
language:English
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