Unit 4A - Intro. Optics and Light

Question 1

Principles of Light

Answer 1

Light travels in straight lines through air as an electromagnetic wave (at the speed of light), and can travel through space without any medium.

Question 2

Luminous v. Non-Luminous Sources

Answer 2

• Luminous source: Produces own light
• Non-luminous source: Doesn’t produce own light

Question 3

Incandescence

Answer 3

• Light from high temperature
• Ex: Heated tungsten wire glowing in lightbulb - Inefficient due to most of energy at tungsten wire lost as heat

Question 4

Electric Discharge

Answer 4

• Light from passing electric current through gas
• Ex: Lightning

Question 5

Phosphorescence

Answer 5

• Light by absorption of UV light resulting in emission of visible light over time
• Ex: Glow-in-the-dark stars

Question 6

Bioluminescence

Answer 6

• Light from organisms as result of chemical reaction with little/no heat produced
• Ex: Fireflies

Question 7

Fluorescence

Answer 7

• Light by absorption of UV light resulting in immediate emission of visible light
• Ex: Fluorescent bulbs

Question 8

Chemiluminescence

Answer 8

• Light as result of chemical reaction with little/no heat produced
• Ex: Glow sticks

Question 9

Triboluminescence

Answer 9

• Light from friction from scratching, crushing, or rubbing crystals
• Ex: Light from quartz crystals

Question 10

Light from Light-Emitting Diode

Answer 10

• Light produced by electric current in semiconductors
• Ex: LED bulbs
• More energy efficient

Question 11

Normal

Answer 11

The perpendicular line to a mirror surface

Question 12

Geometric Optics

Answer 12

The use of light rays to determine how light behaves when it strikes objects

Question 13

Degrees of Visibility

Answer 13

• Opaque: Cannot be seen through at all
• Translucent: Can be seen through at any degree except completely
• Transparent: Can be seen through completely

Question 14

Components of Mirror

Answer 14

• Sheet of glass and thin film of reflective silver/aluminum
• Glass protects thin film on the back and aids physical appearance of mirror.
• Thin film reflects light

Question 15

Real Image

Answer 15

Image formed when light rays meet at particular point after reflection from mirror

Question 16

Virtual Image

Answer 16

Image in which light does not actually arrive at or come from the image location

Question 17

Laws of Reflection

Answer 17

• Flat Surfaces: Angle of incidence = Angle of reflection
• Incident ray, reflected ray, and normal all lie on same plane

Question 18

Image Attributes from a Plane Mirror

Answer 18

• Size: Same [as object]
• Attitude: Upright
• Location: Behind mirror
• Type: Virtual

Question 19

Centre of Curvature “C”

Answer 19

Centre of the sphere of which the curved mirror forms a part

Question 20

Principal Axis

Answer 20

Straight line passing through centre of curvature and focal point

Question 21

Vertex “V”

Answer 21

• The midpoint of the mirror
• The point where the principal axis intersects the mirror

Question 22

Focus “F”

Answer 22

Point where all light rays parallel to principal axis reflected off converge

Question 23

Rules for Concave (Converging) Mirrors

Answer 23

• Light ray parallel to principal axis reflected through focus
• Light ray through center of curvature reflected back on itself
• Ray through F will reflect parallel to principal axis
• Ray at vertex will follow law of reflection

Question 24

Reversibility of Light

Answer 24

Switching the incident and reflected rays of light will still lead the light to follow the same path

Question 25

Object Beyond C, At C or Between C and F

Answer 25

Reflected rays meet in front of mirror, forming inverted real image

Question 26

Object Located At F

Answer 26

Reflected rays parallel and do not intersect neither in front of nor behind the mirror

Question 27

Object Between F and Concave Mirror

Answer 27

Reflected rays diverge, leading brain to extrapolate diverging rays backward to appearance of origin behind the mirror

Question 28

Object Beyond C

Answer 28

Image smaller, inverted, between C and F, real

Question 29

Object Between C and F

Answer 29

Image larger, inverted, beyond C, real

Question 30

Object at C

Answer 30

Image same size, inverted, at C, real

Question 31

Object at F

Answer 31

No clear image

Question 32

Object For Concave Mirrors

Answer 32

Image smaller, upright, behind mirror, virtual

Question 33

Rules for Convex (Diverging) Mirrors

Answer 33

- Ray parallel to principal axis reflected as if it came through focus - Ray aimed at centre of curvature is reflected back upon itself - Ray aimed at virtual focus is reflected parallel to principal axis

Question 34

Images for Convex Mirrors

Answer 34

- Reflected rays from object never cross in front of mirror. - Brain extrapolates rays behind mirror to where they appear to converge (between virtual focus and vertex) - Results in smaller, upright virtual image.

Question 35

Applications of Curved Mirrors

Answer 35

- Concave: Solar cookers, searchlights, satellites - Convex: Security mirrors, side-view mirrors on cars

Question 36

Specular v. Diffuse Reflection

Answer 36

- Specular: Reflection off a smooth surface - Diffuse: Reflection off an irregular/dull surface

Question 37

Components of a Fluorescent Bulb

Answer 37

- Outer shell: Glass tubing - 2nd outer shell: Fluorescent coating - Inner arrow: Direction of current - Dots: Mercury atoms - Ends of bulb: Electrode - Outer arrows: Light

Question 38

Components of a Glow Stick

Answer 38

- Inner stick: Hydrogen Peroxide Solution held by glass vial - Inner Surrounding: Phenyl Oxalate Ester and Fluorescent Dye Solution held by plastic casing

Question 39

How a Glow Stick Works

Answer 39

- 2 chemicals, 1 in a narrow small glass vial - Bending the stick breaks the vial, causing chemicals to mix - Chemical reaction produces visible light

Question 40

Components of an Incandescent Bulb

Answer 40

- Bottom "button": Electrical foot contact - Below surface of bottom: Insulation - Surrounding of bottom: Screw thread contact - Heated wire: Tungsten filament - Filament held by: Support wires - Bulb filled with: Inert gas

Question 41

The light spectrum

Answer 41

ROYGBIV

Question 42

Rays of Light (from lowest to highest energy)

Answer 42

- Radio wave > Microwave > Infrared > Visible > UV > X-ray > Gamma Rays - Higher wavelength, lower energy

Question 43

Wavelength of Visible Light

Answer 43

Between 380 to 780 nanometres

Question 44

Focus for Convex Mirror

Answer 44

Virtual Focus