Optics

Question 1

Define the electromagnetic spectrum. Name the different types from longest to shortest wave.

Answer 1

A classification of EM waves by energy.

• radio waves
• microwaves
• infrared light
• visible light
• ultraviolet
• X-Rays
• gamma rays

Question 2

Wavelength

Answer 2

The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave

Question 3

Frequency and amplitude

Answer 3

• Frequency = number of times something occurs

- Amplitude = maximum extent of a vibration or oscillation (measured from the position of equilibrium)

Question 4

Which type of electromagnetic wave has the longest wavelength? Will its frequency be high or low?

Answer 4

Radio waves; low

Question 5

What are the colours of visible light? List them from longest wave length to shortest.

Answer 5

Red, orange, yellow, green, blue, indigo, violet (ROYGBIV)

Question 6

How do we see colours?

Answer 6

Reflection

Question 7

Refraction

Answer 7

The bending/ change in direction of light when travelling from one material to another

Question 8

When light travels from a less optically dense material to one that is more dense, where does the light refract in relation to the normal?

Answer 8

Toward

Question 9

Law of reflection

Answer 9

1) angle of incidence = angle of reflection

2) incident ray, reflected ray and normal lie in the same plane

Question 10

What causes refraction?

Answer 10

Light’s change in speed when travelling between the mediums, causing it to change direction

Question 11

State the rules of refraction.

Answer 11

1) Light bends toward the normal when speed is less inside the second medium
2) light bends away from the normal when speed is greater

Question 12

Using examples, compare specular reflection with diffuse reflection.

Answer 12

Specular reflection of light is off of a smooth surface (still water, flat mirror), whereas light reflects off an irregular surface in diffuse reflection (crumpled aluminum foil).

Question 13

transparent, translucent and opaque

Answer 13

• transparent = see through
• translucent = partially see through
• opaque = solid (can’t see through). It absorbs or reflects the incident light

Question 14

Differentiate a concave mirror from a convex mirror. What are their special characteristics?

Answer 14

Concave mirrors cause light rays to converge, as opposed to diverging like in convex mirrors. Convex mirrors always produce a virtual image.

Question 15

Reversibility of light

Answer 15

Principal where light follows same path (switches direction) even if the incident and reflected rays switch

Question 16

Define and describe partial reflection & refraction.

Answer 16

Property that states light can be both reflected and refracted at the same time.
- some incident light refracts, while others reflect (two-way mirrors)

Question 17

Examples of concave and convex mirrors

Answer 17

Concave: make-up and shaving mirrors
Convex: security & side-view mirrors

Question 18

Index of Refraction

Answer 18

• ratio of speed of light in vacuum to speed of light in a medium

Question 19

What are the rules for lenses?

Answer 19

1) light ray parallel to principal axis = reflected through focus
2) light ray through centre of curvature = reflected back to itself
3) light ray through F = reflected parallel to principal axis

Question 20

Critical Angle (water & diamond)

Answer 20

angle of incidence that results in angle of refraction to be 90º
- Water: 48.8º & diamond: 24.4º

Question 21

Total Internal Reflection

Answer 21

angle of incidence > critical angle, turning a refracted ray into a reflected ray. Occurs when

1) light is travelling more slowly in first medium than second
2) angle of incidence is large enough that no refraction occurs

Question 22

State two phenomena related to refraction and describe how they work.

Answer 22

Flattened sun
- when sun is closer to horizon, light from the bottom is refracted more than the light from the top because they have a greater angle of incidence

Mirage
- index of refraction decreases as light travels from cool air to warmer air, resulting in light refracting farther away from normal as air temperature increases

Shimmering
- multiple virtual images of moon along surface of water also as a result of light passing through different temperatures of air

Question 23

Dispersion

Answer 23

separation of white light into its spectrum (such as in a rainbow)

Question 24

Why is the path of light ray through a lens simplified in diagrams?

Answer 24

Because there are always 2 refractions in a lens: air - glass and glass - air

Question 25

Emergent Ray

Answer 25

light that leaves lens post-refraction (from a rectangular glass prism, it is parallel but displaced sideways from incident ray where the amount of displacement depends on the thickness of the prism)

Question 26

Describe the images in a converging lens.

Answer 26

As object moves toward lens, the image gets larger.

Question 27

Describe the images in a diverging lens.

Answer 27

• light rays appear to come from F

- smaller, upright, virtual and on the same side of the lens

Question 28

Explain how the eye functions.

Answer 28

• iris controls how much light enters
• lens and cornea = converging lens (focus, converge, refract light)
• retina converts light into electrical signal, using optic nerve to communicate with the brain
• cornea produces a smaller, real, inverted image that the brain flips to be upright

Question 29

Accommodation (eyes)

Answer 29

changing of the shape of eye lens by muscles to allow formation of focused images on retina

Question 30

Describe hyperopia (far-sightedness)

Answer 30

inability to focus on near objects as the light does not refract well enough resulting in an image behind the retina (needs positive meniscus)

Question 31

Describe myopia (near-sightedness)

Answer 31

inability of eye to focus on far objects because they focus in front of the retina (needs negative meniscus)