Grade 10 Physics Optics
What is light (8)
Reflection (bounce back)
Refraction (go through)
Fast (travels 3 x 10 m/s- 300,000,000 m/s ⁸
Colour (ROYGBIV)
To see
Bright warm colours (carries energy)
Diffraction
How can we see light?
We see light through luminous and non-luminous objects
Luminous-gives off light (sun, light bulb)
Non-luminous – Doesn’t give off light (book, table, binder, pencil, box, bed etc.)
Can we see light travel?
We cannot see light travel from point A to points because it travels so fast, which means we can only
see it when it
hits our eyes.
For a laser, if we spray water we can see the line.
_________________________________________________________________________________________
Law of Reflection
Angle of Incidence= Angle of Reflection
The Incident Ray, Normal and The Reflected Ray All Line in The Same Vertical Plane
Incident Ray - Incoming Ray
Reflected Ray-Bounce Off
For Mirror for Full Body Get A Mirror Half Your Height
Virtual Image - Image Can Be Seen Not Formed
Real Image - Image Can Be Seen and Formed
Luminous Objects - Objects That Produce Light
E.G. Light Bulb or The Sun
Non-Luminous Objects - Objects That Don’t Produce Light E.G. Book or Rock
Terms in Reflection Mirror Diagram:
Normal - Perpendicular to Mirror, Invisible
Incident Ray - Incoming Ray
Reflected Ray - Outgoing Ray
Angle of Incidence - Angle Between Incident Ray and Normal
Angle of Reflection - Angle Between Reflected Ray and Normal
Properties of Light:
Light Travels in A Straight Line
Light Can Change Its Direction When Object Is in Its Path E.G. Water or Mirror
Light Can Be Reflected by Objects
Terms
F- Focus
C- Center of Curvature
V- Vertex
SALT
Size: Same Size Larger, Smaller
Grade 10 Physics Optics
Attribute: Upright Converted
Location: Where Image Is
Type: Real/ Virtual
Salt of Plane Mirror
Size: Same
Attribute: Upright
Location: Same Distance Behind
Type: Virtual
Salt of Pinhole Camera
Size: Smaller
Attribute: Inverted
Location: Behind the Object
Type: Real
If pinhole camera further away from object - the size of image is smaller and blurred
If wax paper is further from pin hole - size of image is bigger
If there are three holes on the camera - three images and image is blurry
If hole is bigger - image is blurred but brighter
*Eyes work like pinhole camera*
*Pinhole camera should have a light proof box because the image will be clearer and contrasted*
Concave Mirror
Convex Mirror
Grade 10 Physics Optics
Facts – Concave mirror
Object At F: No Image
Object Inside F: Virtual Image
How is light produced?
Light from Incandescence
Light from Phosphorescence
Electric Discharge
Light from fluorescence
Light from Chemiluminescence
Light from Bioluminescence
Light of Triboluminescence
Light from Light Emitting Diode (LED)
Light from Incandescence
Objects get hotter and hotter produce red, orange, yellow, and blush (The hottest light) light.
oLight from candle
Electric discharge
A flash of lightening or neon sign
An electric current passing through a gas will produce light of specific colour.
oAn advertisement sign emitting light
Light from Phosphorescence
Glow in the dark toy contains a coating of phosphorus which absorbs UV light and release visible light
over a
period of time.
Grade 10 Physics Optics
oGlow in the dark toy
Light from Florence
Absorbs UV light and immediately releases visible light
oCFL bulb emitting light
oHighlighter
Light from Chemiluminescence
When 2 chemicals mix together the by-product visible light with no heat is produced.
oGlow stick
Light from Bioluminescence
In body of organisms with oxygen and Lucifer in.
o Firefly
Light from Triboluminescence
The visible created when certain crystals are rubbed or pressed
oLight produced when crystals rub together
Light from Light Emitting Diode (LED)
An electric current flow in a definite direction of the semi-conductor making it to emit light
Christmas light, Traffic light, House number plate of Mr. Ho’s
Advantage of LED over Incandescent
LED doesn’t get hotter and hotter
LED has longer lifespan than incandescent
The Light Spectrum: Electromagnetic Spectrum
1. Radio waves
2. Microwaves
3. Infrared lights
4. Visible lights
5. Ultraviolent (UV) light
6. X rays
7. Gamma Rays
Radio waves
AHIGM Radio
TV signal
Cell phones communication
Radar
Astronomy- discovery pulsars
Microwaves
Telecommunications
Microwave ovens
Astronomy- background
Radiation associated with big bang
Infrared light
Remote control
Physical therapy
Lasers
Heat detection and remote sensing
Keeping food warm in fast food restaurants
Astronomy (discovery of chemical composition of bodies
Visible lights
Human vision
Theatre/concert lighting
Grade 10 Physics Optics
Rainbows
Visible layer
ROYGIV
Astronomy (optical telescope, chemical composition of body.
Ultraviolet light
Causes tan and sun burn
Increases chances of getting cancer
Stimulates production of vitamin D
Kills bacteria in food and water
Black lights
UV lights
X-ray
Medical imaging
Security equipment
Cancer treatment
Astronomy (study of binary stars system black holes the centre of galaxy.)
Gamma ray
Cancer treatment
Astronomy (study of nuclear processes in the universe
Product of some nuclear decay
Sheerness – Type of Material
Transparent (see through)
Translucent (See through but not well)
Opaque (No light goes through)
Refraction- Calculation Terms
n – index of refraction
i – incidence
r – refracted angle
c – vacuum (air)
v – medium (not air)
Equations
To Find Index of Refraction (n) – Speed of light in vacuum to the speed of light in medium
𝑐
𝑛=
𝑣
To Find Angle of Incidence and Refraction – One medium is air
sin 𝑖
𝑛=
sin 𝑟
To Find Angle of Incidence and Refraction –Both mediums (not air) : 𝑛1 𝑠𝑖𝑛𝜃1 = 𝑛2 𝑠𝑖𝑛𝜃2
Drawing Angle in Mediums
Drawing Angle in Mediums
Grade 10 Physics Optics
Total Internal Reflection
Two Criteria
1. Light must travel in a straight line
2. Incident angle is ≥ critical angle
n – refracted angle
c – critical angle
Equation
1
1
→ 𝑐 = sin−1 ( )
𝑛
𝑛
What Is a Critical Angle/ Total Internal Reflection
When the angle of refraction is equal to 90°, the angle of incidence is called the critical angle. When angle of
incidence greater than the critical angle, the light cannot pass through the surface – it is all reflected. This is
called total internal reflection. Total because all of the energy is reflected.
Special Angle
Usually 45° is a special angle because commonly, critical angles are 45°. So, angles of median going to air is
less that 45°, critical angles occur often.
sin 𝑐 =
Concave Lens
Diverging Lens
Spreads parallel light rays apart after refraction so that is seems they come from a virtual focus
 Main focus (f) of a diverging lens is on the same side of the lens as the incident rays
SALT – Always the same
Real Depth Vs Apparent Depth
Grade 10 Physics Optics
Real Depth – From what the eye sees it is bent
Apparent Depth – Looks like a straight line in the water
Thins Lens Equations and Magnification Equation
Terms
2f
Two times f
If f is 5 2f is 10
Binoculars and Periscopes – Diagrams
Why Do We Use Prisms Instead of Mirrors?
Prisms don’t have multiple images unlike mirrors.
Grade 10 Physics Optics
Optical Fibres
How does Fibre Optics work?
Diagram showing refraction, critical angle, and total internal reflection between two media, air and water.
The Science Behind Optical Fibers
When a ray of light enters a dense medium, such as plastic or glass, it is refracted, or directed in a different
direction than its original path.
Every medium that light can pass through has a critical angle, or maximum angle such that light entering it is
transmitted without being absorbed. This critical angle is dependent on the refractive indices of both mediums.
Fiber optics is the use of transparent, flexible fiber to transmit light from one end to the other.
Fiber optic communication begins with converting an electrical signal to light. This light, generated by a laser
Grade 10 Physics Optics
diode (LD) or light emitting diode (LED) is transmitted through one end of an optical fiber and received on the
other by a photodiode.
Fiber optics leverages the total internal reflection properties of optical fiber, which is also a function of the
refractive index of the fiber’s core and its cladding. With the right ratio between the two, light from one end is
reflected at the mediums’ boundary, or interface, and guided through the length of the fiber.
Total internal reflection of light in a section of optical fiber.
Optical physics is the primary field of study that concerns fiber optics. Many of the fundamental principles of RF
transmission line theory, such as attenuation, insertion loss, return loss, and dispersion, also apply.
Fiber optics: endoscopes to telephones
Fiber optics is one application of total internal reflection that is in wide use. In communications, it is used to
transmit telephone, internet, and cable TV signals. Fiber optics employs the transmission of light down fibers of
plastic or glass. Because the fibers are thin, light entering one is likely to strike the inside surface at an angle
greater than the critical angle and, thus, be totally reflected. The index of refraction outside the fiber must be
smaller than inside. In fact, most fibers have a varying refractive index to allow more light to be guided along
the fiber through total internal refraction. Rays are reflected around corners as shown, making the fibers into
tiny light pipes.
Grade 10 Physics Optics
Light entering a thin optic fiber may strike the inside surface at large or grazing angles and is completely reflected if
these angles exceed the critical angle. Such rays continue down the fiber, even following it around corners, since the
angles of reflection and incidence remain large.
Bundles of fibers can be used to transmit an image without a lens, as illustrated in the pictures below . The output of a
device called an endoscope is shown in (b). Endoscopes are used to explore the interior of the body through its natural
orifices or minor incisions. Light is transmitted down one fiber bundle to illuminate internal parts, and the reflected light
is transmitted back out through another bundle to be observed.
(a) An image “A” is transmitted by a bundle of optical fibers. (b) An endoscope is used to probe the body, both
transmitting light to the interior and returning an image such as the one shown of a human epiglottis (a structure at the
base of the tongue). (credit b: modification of work by “Med_Chaos”/Wikimedia Commons)
Fiber optics has revolutionized surgical techniques and observations within the body, with a host of medical diagnostic
and therapeutic uses. Surgery can be performed, such as arthroscopic surgery on a knee or shoulder joint, employing
cutting tools attached to and observed with the endoscope. Samples can also be obtained, such as by lassoing an
intestinal polyp for external examination. The flexibility of the fiber optic bundle allows doctors to navigate it around
small and difficult-to-reach regions in the body, such as the intestines, the heart, blood vessels, and joints. Transmission
Grade 10 Physics Optics
of an intense laser beam to burn away obstructing plaques in major arteries, as well as delivering light to activate
chemotherapy drugs, are becoming commonplace. Optical fibers have in fact enabled microsurgery and remote surgery
where the incisions are small and the surgeon’s fingers do not need to touch the diseased tissue.
Mirage
Occurs on sunny days/ places
Sun heats roads and road heats surrounding air
Cool air light travels slow
Warm air light travels fast
Diagram
Lens Application
Camera
Projector
Grade 10 Physics Optics
Compound Microscope
Refracting Telescope
Grade 10 Physics Optics
The Human Eye
Normal Eye
Focuses light from a nearby object on to the retina
Far-Sighted (Hyperopia)
Grade 10 Physics Optics
Focuses light from a nearby object behind the retina
A corrective converging lens (convex lens) will correct far-sightedness
Corrective lens with positive Meniscus – same affect as a convex lens
oBoth are thicker in the middle
Near-sighted (Myopia)
Near – sighted eye focuses light from a distant object in front of the retina
A corrective diverging lens will correct near-sightedness
A corrective lens with negative meniscus will have the same affect as a diverging lens because it is
thinnest in the middle.