Download Introduction to Drawing Ray Diagrams Types of

Introduction to Drawing Ray Diagrams
Types of Mirrors and Lenses
 Plane Mirror – a mirror with a flat, reflective surface
 Convex Mirror – a mirror whose reflecting surface curves outward
 Concave Mirror – a mirror whose reflecting surface curves inward
 Lens – a transparent device with at least 1 curved surface that changes
the direction of light passing through it (refracts light)
*Rays are refracted at the surfaces of lenses according to Snell’s
Law*
 Converging Lens – a lens that causes parallel light rays to come
together, so that they cross at a single focal point (convex lenses)
 Diverging Lens – a lens that causes parallel light rays to spread apart,
so that they appear to emerge from the virtual focal point (concave
lenses)
Terms for Ray Diagrams
 Optical Centre (O) / Vertex (V) – the geometric centre of all lenses
 Optical Axis (OA) – an imaginary vertical line through the optical
centre
 Principle Axis (PA) – a horizontal line drawn through the optical
centre
 Focal Point (F) – the point on the principal axis through which a
group of rays parallel to the principal axis are refracted *F = ½ C
 Focal length (f) – the distance between the focal point and the optical
centre, measured along the principle axis
 Centre / Radius of Curvature (C) – the centre of a sphere whose
surface has been used to make the mirror or lens
OA
O or V
PA
C
F
F
f
C
Drawing Mirrors and Lenses
1. Plane Mirror
4. Convex Lens
2. Convex Mirror
3. Concave Mirror
5. Concave Lens
4 Image Characteristics – SALT
 S – Size or Magnification
Is the image smaller, larger, or the same size in comparison to the
object?
 A – Attitude
Which way is the image oriented compared to the object: upright
or inverted?
 L – Location
Where is the image relative to the mirror or lens? Is the image
behind or in front of the mirror or lens? Where is the image in
relation to C and F?
 T – Type
Is the image real or virtual?
*Real images can be projected onto a screen.
*Virtual images cannot be projected onto a screen.
Ray Diagrams
1. Images in a Plane Mirror
 Ray diagrams as per our SONG
 F and C do not exist, as there is no radius of curvature
 Memorize SALT for a plane mirror
S – image is the same size as the object
A – image is upright
L – image is the same distance behind the mirror, as the object is in front of
the mirror
T – image is virtual (image is behind mirror – rays converge behind mirror)
2. Images in a Convex Mirror
 F and C are on the right side of the mirror
 Always draw rays starting from the top of the object
 Solid lines are used on the left; dotted lines are used on the right
Steps for Locating Image
Draw a ray // to PA, stopping at the mirror. From the edge of the mirror,
angle ruler through F on the right side of the mirror. Extend this ray
backwards on the left.
Draw a ray through C. Place a dot where the first 2 rays intersect.
Draw a ray to O, until the mirror is reached. Angle the ruler downwards
towards the left, so that the ruler intersects the point. Draw this ray.
S – smaller
A – upright
L – behind mirror (between O and F)
T – virtual ( rays converge behind mirror)
See example on DOV Camera.
3. Images in a Concave Mirror
1
2
3
4
5
Steps for Locating Image
For (1-3): Draw ray #1 // to PA, stopping at the mirror. Angle ruler, so the
same ray is refracted through F. Draw ray #2 through F, touching mirror
below PA. Continue this ray // to PA. Place a dot at the intersection. Draw
ray #3 to O, and angle ruler so that this ray reaches the point of intersection.
All rays will be on left side of mirror with solid lines.
For 4: Draw ray #1. Ray #2 cannot be drawn. Draw ray #3 to O, and then
continue this ray // to ray #1.
For 5: Draw ray #1. Extend the ray intersecting F backwards on the right
side of the mirror using a dotted line. Ray #2 cannot be drawn. Draw ray #3
to O, and angle ruler so that ray #1 and ray #3 are skew rays. Extend ray #3
backwards with a dotted line. Draw image.
S
A
L
T
1
Smaller
than object
2
Same size
Inverted
At C
3
Larger than
object
Between F
Beyond C
&C
Real (rays converge in front of mirror)
See 5 DOV Camera examples.
4
No image
(reflected
rays are //
and never
converge)
5
Larger than
object
Upright
Behind
mirror
Virtual (rays
converge
behind
mirror)
4. Images in a Convex Lens
1
2
3
C
4
5
F
F
C
Steps for Locating Image
For (1-3): Draw ray #1 // to PA, stopping at lens. Extend this ray through F
on the right side. Draw ray #2 through O, intersecting through ray #1. Place
a dot where the 2 rays intersect. Draw ray #3 through F on the left side,
stopping at lens. Continue ray // to PA, through the intersection point.
For 4: Draw ray #1. Draw ray #2 through O, realizing rays will never
converge (// rays). Ray #3 cannot be drawn.
For 5: Draw ray #1. Extend the ray intersecting F backwards on the left side
of the lens using a dotted line. Draw ray #2 through O, ensuring ray #1 and
ray #2 are skew rays. Extend ray #2 backwards with a dotted line. Draw
image.
S
A
L
T
1
Smaller
than object
Between F
&C
2
Same size
Inverted
At C
3
Larger than
object
Beyond C
Real (rays converge after going through
lens)
See 5 DOV Camera examples.
4
No image
(refracted
rays are //
and never
converge)
5
Larger than
object
Upright
Same side
as object
(left of
object)
Virtual (rays
must be
extended
back to
converge)
5. Images in a Concave Lens
Steps for Locating Image
Draw ray #1 // to PA, stopping at lens. Angle ruler so that ray passes through
F on the left side with a dotted line. Extend this ray backwards on the right
side with a solid line. Draw ray #2 through F on the right side. This ray will
be solid on the left, and dotted on the right. Angle ruler to create ray #3 // to
PA, ensuring there is a POI with the lens. Ray must be dotted on left and
solid on the right. Draw ray #4 through O with a solid line. Ray #1, 3, and 4
will intersect.
S – smaller than object
A – upright
L – same side as object (between F and lens)
T – virtual (rays must be extended back to converge)
See DOV Camera example.