Optics Flashcards
Define the electromagnetic spectrum. Name the different types from longest to shortest wave.
A classification of EM waves by energy.
- radio waves
- microwaves
- infrared light
- visible light
- ultraviolet
- X-Rays
- gamma rays
Wavelength
The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave
Frequency and amplitude
- Frequency = number of times something occurs
- Amplitude = maximum extent of a vibration or oscillation (measured from the position of equilibrium)
Which type of electromagnetic wave has the longest wavelength? Will its frequency be high or low?
Radio waves; low
What are the colours of visible light? List them from longest wave length to shortest.
Red, orange, yellow, green, blue, indigo, violet (ROYGBIV)
How do we see colours?
Reflection
Refraction
The bending/ change in direction of light when travelling from one material to another
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?
Toward
Law of reflection
1) angle of incidence = angle of reflection
2) incident ray, reflected ray and normal lie in the same plane
What causes refraction?
Light’s change in speed when travelling between the mediums, causing it to change direction
State the rules of refraction.
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
Using examples, compare specular reflection with diffuse reflection.
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).
transparent, translucent and opaque
- transparent = see through
- translucent = partially see through
- opaque = solid (can’t see through). It absorbs or reflects the incident light
Differentiate a concave mirror from a convex mirror. What are their special characteristics?
Concave mirrors cause light rays to converge, as opposed to diverging like in convex mirrors. Convex mirrors always produce a virtual image.
Reversibility of light
Principal where light follows same path (switches direction) even if the incident and reflected rays switch
Define and describe partial reflection & refraction.
Property that states light can be both reflected and refracted at the same time.
- some incident light refracts, while others reflect (two-way mirrors)
Examples of concave and convex mirrors
Concave: make-up and shaving mirrors
Convex: security & side-view mirrors
Index of Refraction
- ratio of speed of light in vacuum to speed of light in a medium
What are the rules for lenses?
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
Critical Angle (water & diamond)
angle of incidence that results in angle of refraction to be 90º
- Water: 48.8º & diamond: 24.4º
Total Internal Reflection
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
State two phenomena related to refraction and describe how they work.
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
Dispersion
separation of white light into its spectrum (such as in a rainbow)
Why is the path of light ray through a lens simplified in diagrams?
Because there are always 2 refractions in a lens: air - glass and glass - air
Emergent Ray
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)
Describe the images in a converging lens.
As object moves toward lens, the image gets larger.
Describe the images in a diverging lens.
- light rays appear to come from F
- smaller, upright, virtual and on the same side of the lens
Explain how the eye functions.
- 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
Accommodation (eyes)
changing of the shape of eye lens by muscles to allow formation of focused images on retina
Describe hyperopia (far-sightedness)
inability to focus on near objects as the light does not refract well enough resulting in an image behind the retina (needs positive meniscus)
Describe myopia (near-sightedness)
inability of eye to focus on far objects because they focus in front of the retina (needs negative meniscus)
