Grade 10 Applied SNC2P Light & Application of Optics
Light – is a form of energy can travel like a wave through empty space and some materials; light is a special kind of electromagnetic wave.
Electromagnetic wave – waves that carry electrical energy and magnetic energy; invisible and can travel through a vacuum; does not need
particles in order to travel
Electromagnetic Spectrum – a representation of the types of electromagnetic
waves arranged according to wavelength
Wavelength – the distance from the peak of one part of the wave to the next
peak
Visible light (spectrum) – is a very small part of the electromagnetic spectrum
The longest wavelength of visible light are red and the shortest wavelengths
are blue
Luminous objects – objects that produce light; can be both natural (i.e.
fireflies) and artificial (i.e. neon signs)
Non-luminous objects – objects that do not produce their own light (i.e.
moon)
Light-producing technology
Incandescence - a substance that gives off light because it is heated to a high temperature
Luminescence – emission by light by a material or object that has not been heated (all technologies below are types of luminescence)
Electric discharge – when electron move from one end of a sealed glass tube to the other. They collide with gas particles and transfer
energy to them and the gas particles release the energy as light
Phosphorescence – process of producing light by the absorption of UV light resulting in the emission of visible light over a long period of
time
Fluorescence – the immediate emission of visible light as a result of absorption of UV light; the UV light hits the fluorescent coating on
the outside of the tube and light is produced
Chemiluminescence – direct production of light as a result of a chemical reaction
Examples
Wood fires, candles, incandescent light bulb
Bioluminescence – production of light in living organisms as a result of a chemical reaction
Triboluminescence – the production of light from friction as a result of scratching, crushing, or rubbing certain crystals
Fireflies
Rubbing quarts
Light can be:

Transmitted – light goes through an object
o
Transparent object transmits all or most light with no change in direction (i.e. window)
o
Translucent object transmits some light and scatters it in different direction (i.e. frosted glass)
o
Opaque object – does not transmit light; it reflects or absorbs light (i.e. book)

Reflected – light “bounces off” the surface of the object and changes direction

Absorbed – light is absorbed and the energy is converted to heat; no light is reflected from an object that
absorbs light
Colour of an object is determined by the colour that it absorbs, reflects, or transmits
Neon lights, street lights
Glow in the dark t-shirts
Fluorescent light bulbs
Glow sticks
Transparent
Translucent
Opaque
Additive Colour
When white light hits
an opaque object,
this apple appears
red because it reflects
the red wavelength
and absorbs all the
other colours
When white light hits a
coloured transparent or
translucent object, such as
blue cellophane, the object
absorbs every colour except
its own colour; that colour will
be transmitted and reflected
Additive Colour – Primary colours: red, green, blue; when two primary colours combine produces
secondary colour: yellow, magenta, cyan; all three primary colours combine to produce white
Subtractive Colour – Primary colours: yellow, magenta, cyan; secondary colours: red, green, blue are
produced when subtractive primary colours are subtracted from white light. When all three subtractive
primary colours are subtracted from white light, the result is black.
Subtractive Colour
Grade 10 Applied SNC2P Light & Application of Optics
Reflection – the change in direction of a light ray when it bounces off a surface
Law of Reflection:

angle of incidence = angle of reflection

the incident ray, reflected ray, and the normal (a line that is perpendicular
to the surface where a ray of light meets the surface) lie in the same plane
Diffuse Reflection – occurs on a dull or rough surface, because the surface is not
smooth, light is reflect in all directions, but the laws of reflection still apply
Ray Model of Light
- ray – a straight line with an arrowhead that shows the direction in with light waves are travelling
- uses straight lines to show how light interacts with objects
- used to show how light travels through some substances and reflects off others; used to predict and understand the way light behaves
Plane mirror – a mirror with a flat, reflective surface; images in a plane mirror is laterally inverted (backwards)
Concave mirror – a mirror whose reflecting surface curves inward; rays that come off the concave mirror get closer together, they converge;
a concave mirror is a converging mirror
Convex mirror – a mirror whose reflecting surface curves outward; Rays that come off the convex mirror get farther apart, they diverge
away; a convex mirror is a diverging mirror
How to do a Ray Diagram for an Object between a concave mirror and the Focal Point (F) (see figure)
Step 1 Draw the principal axis (line perpendicular to the centre of the mirror) and a line with a slight curve to represent the concave mirror. Mark F. Draw
an object between the F and the mirror. F = focal point – the point at which reflected rays meet.
(Note: C = centre of curvature, which is the centre of the sphere that the mirror fits on. The focal point is ALWAYS halfway between the centre of the
curvature and the mirror)
Step 2 Draw a ray (shown in blue) from the top of the object toward the mirror and parallel to the principal axis; draw the reflected ray back through the
focal point.
Step 3 Position your ruler and draw the ray (shown in green) from the top of the object to the mirror. Draw the reflected ray backward and parallel to the
principal axis.
Step 4 Extend the reflected rays behind the mirror with dashed lines. Draw the image between the point where the dashed lines meet the principal axis.
Characteristics of Images in Curved Mirrors:
Location of the image (image distance is longer/shorter than the object distance)
Orientation (upright or inverted)
Size (describes the size of the image; whether larger or smaller than the object also known as the magnification of the image)
Type (if the image is virtual or real)
Virtual image – an image in which is formed when the reflected rays do not meet and you have to extend the rays backwards
Real image – an image that is formed when reflected rays meet
Lens – a type of glass or plastic that has at least
one curved side: may be concave, convex, or
plane
Converging lens – a lens that makes parallel
light rays come together (converge)
Diverging lens – make light rays move apart
(diverge)
plane mirror
4
2
1
3
Image
Location: image distance
longer than object
distance
Orientation: upright
Size: larger than the
object
Type: virtual
Refraction – the change in direction of light when it crosses a
boundary between two media; the bending effect of light
when it crosses a boundary between two media;
Medium – any substance or material that light is travelling
through (plural = media)
Refracted ray – the ray after crossing a boundary between two
media
Angle of refraction – the angle between the refracted ray and
the normal