1. PHYSICS InClass by SSL Technologies with S. Lancione Exercise-46
High School
InClass
by SSL Technologies
with S. Lancione
Exercise-46
Intro to Optics
Part 2 /2

2. Intro to Optics
PART-2 /2
In studying optics, it is convenient to classify objects into those that
emit light (luminous) and those that reflect light (non-luminous):
LUMINOUS (originate light)
NON-LUMINOUS or ILLUMINATED (do not originate light)
Incandescent Opaque (light cannot pass through)
Neon Transparent (light and images pass through)
Fluorescent Translucent (light passes through, images do not)
BEAM OF LIGHT: A beam of light is a "bunch" of light rays.
CONVERGENCE: When rays of light come together to meet at
a point, they are said to converge.
DIVERGENCE: When rays of light go away from a point, they are
said to diverge.
MEDIUM: A medium is the material through which light travels.
Optical mediums are classified according to density.
The more "optically dense" a material is, the slower
light travels in that medium.
Click

3. Intro to Optics THE PRIMARY COLORS
Monochromatic light is light of one color.
Polychromatic light is light of many colors.
In everyday language we use names to represent monochromatic
light such as red, orange, yellow, green, blue and violet.
Furthermore, each of these colors has a variety of different shades.
Collectively, all the different colors form the “light band” which is
part of the “electromagnetic spectrum”.
Click

4. Intro to Optics
Red, green and blue light (RGB) are called the primary colors.
Adding these three primary colors together forms “white” light.
Adding pairs of the primary colors form the secondary colors.
Click

5. Intro to Optics
The color of an object is determined by the color (or colors)
it reflects.
Suppose white light shines on a red object. The object will
absorb all the colors except red. Thus, it is red.
Study the illustration below.
Click

6. COLOR THEORY Inks Lights Additive color theory
Subtractive color theory
Primary colors: RGB
Primary colors: CMY
Red – Green – Blue
Cyan – Magenta – Yellow
Inks
Lights
Cyan = Green + Blue
Red = Magenta + Yellow
Magenta = Red + Blue
Green = Cyan + Yellow
Yellow = Red + Green
Blue = Cyan + Magenta
White = Red + Green + Blue
Black = Cyan + Magenta + Yellow
Click

7. Intro to Optics Penumbra (grey) Umbra (black) SHADOWS
Shadows are formed when light is obstructed. The light may be
totally obstructed thereby forming a dark shadow known as an
umbra, or it may be partially obstructed thereby forming a gray
shadow known as a penumbra.
Penumbra (grey)
Umbra (black)
Click

8. Intro to Optics Click From the side view, we have two rays
For example, in diagram-A below, a point source of light encounters an
obstacle (a disc) causing an umbra (total darkness).
In diagram-B, a large source of light causes both an umbra and a penumbra.
Note that when the source is a point, the shadow consists of an umbra
(total darkness) with a well defined outline.
From the side view,
we have two rays
(one to the top of the
obstruction, one to
the bottom of the
obstruction) to define
the shadow (the light
source has no top and
bottom portions).
Click

9. EXERCISES

10. Question-1 Define the following terms: a) Beam of light
A stream of photons emanating (coming from) a light source.
b) Medium
The material through which light travels.
c) Opaque
A material that blocks light (light cannot pass through).
d) Transparent
A material through which light and images pass through.
e) Translucent
A material through which light can pass through but
images cannot pass through.
Click
Click
Click
Click
Click
Click

11. Question-2 Define the meaning of the terms monochromatic and
polychromatic light.
Monochromatic is light consisting of only a single color.
Polychromatic is light consisting of many colors.
Click
Click
Click

12. Question-3
Draw 5 rays of light that are parallel, converging and diverging.
Click
Click

13. Question-4
What does RGB stand for?
Red, Green and Blue.
Click
Click

14. Question-5
Fill in the primary and secondary colors in the chart below:
Red
Green
Blue
Yellow
Cyan
Magenta
Click
Click

15. Question-6 Define an umbra and explain how it is formed.
The umbra consists of total darkness and is caused by the
total obstruction of the light rays.
Click
Click

16. Question-7 Define an penumbra and explain how it is formed.
The penumbra consists of partial darkness and is caused
by the partial obstruction of light rays.
Click
Click

17. Question-8 In your own words, define light intensity.
Light intensity (also known as brilliance) refers to the total
number of photons emitted by a light source per second.
Click
Click

18. Question-9
Sketch the electromagnetic spectrum and indicate the position
of light.
Click
Click

19. Question-10 In the given diagram, measure the length of the umbra and
penumbra of the shadow formed by the obstruction (line).
Click
Click

20. Question-11 By definition
A beam of white light strikes a glass prism producing an array of different colors as illustrated below.
What optical phenomena does this represent?
A) Specular reflection
B) Total internal reflection
C) Diffusion
D) Dispersion
By definition
Click
Click

21. Question-12
The diagram below illustrates light coming from the sun to the earth with the moon in between.
Which of the following statements correctly describes the shadow of the moon on the earth?
I- Region Y is the penumbra
II- Regions X and Z are the umbra
III- Regions Y is the umbra
IV- Regions X and Z are the penumbra
A) I and II B) I and IV C) II and III D) III and IV
Click

22. Question-13
The diagram below illustrates a white light source, a blue filter and a yellow object.
Blue filter
All the colors
Blue
What color will the object appear?
A yellow object illuminated by white light will absorb all the colors except yellow. A blue filter will filter all the colors except blue. Thus, when the blue light strikes the yellow object, it will be absorbed and the object will appear black (since it reflects no light).
A) White
B) Black
C) Yellow
D) Blue
Click
Click

23. Question-14
A green filter is placed between a red light source and an object.
Red light source
Green filter
White object
What color is the object?
A) Red
B) Green
C) Yellow
D) White
E) Black
A green filter will block (absorb) all colors except green. Since the light source gives off red light, the green filter will absorb the red light causing no light to fall on the object.
Click
Click

24. Question-15
Three different colored objects X, Y and Z, are illuminated by three projectors. Each projector emits a different colored light.
The first projector causes object X to appear blue while the other objects appear black.
The second projector causes objects X and Y to appear red while object Z appears black.
The third projector causes objects X and Z to appear green while object Y appears black.
What color do the objects appear if while light is used to illuminate the objects?
White
Red
Green
Object-X Object-Y Object-Z
A) Blue Black Black
B) Blue Red Green
C) White Red Green
D) White Black Red
E) White Black Green X Y Z 1 2 3
Click

25. SSLTechnologies.com/science
The end
SSLTechnologies.com/science