Vocab
Reflection
The change in direction of a wave when it bounces off a barrier
Angle of Refraction
•Light bending toward the normal indicates the speed is slower in the second medium.
•Light bending away from the normal indicates the speed is faster in the second medium.
•The changing speed is what causes the change in direction.
•The frequency of the light does not change!
Critical Angle
- The angle of incidence that provides an angle of refraction of 90 degrees
- A ray that is greater than the critical angle cannot leave the medium and all of the light is reflected
- Diamonds sparkle because most of the light rays hitting the stone are internally reflected . . . Diamond has a high index of refraction
- Thicker in the center than edges
- Refracts parallel light rays so that the rays meet a point (the focal point)
- Forms REAL IMAGES and VIRTUAL Images depending on position of the object
Determining the features of a concave lense
Diffraction
The bending of light around a barrier
When light strikes a surface along the perpendicular, the angles of incidence and refraction are:
ZERO
How do mirages form?
•On hot days, a hot layer of air is in contact with the ground with cooler air above it
•Light travels faster in the hot air
•This increase in speed causes a bending of the light rays
•The observer sees light from the sky as if it’s coming from the ground
Concave (diverging) Lenses
- Lenses that are thicker at the edges and thinner in the center
- Rays passing through it spread out
- All images are VIRTUAL, UPRIGHT, REDUCED
Refraction
The changing direction of a wave as it passes from one medium to another
Index of Refraction
- A number that tells how much a material slows down light
- It represents how much slower the light travels in the medium as compared to a vacuum.
- Equation: n = c/v
- The separation of light into its spectrum is called dispersion
- Red light is bent the least, while violet light is bent the most
- The index of refraction depends on the color, or frequency, of light
- A rainbow is a natural dispersion of light
Uses of Lenses
Converging (Convex): Used to focus on objects
- Magnifying glasses, cameras, binoculars, telescopes, microscopes, glasses, movie projectors, our eyes
Diverging (Concave): Used to get a wider view
- Flashlights, glasses, door peepholes, telescopes, cameras
What affects how much light refracts?
1. The angle the light strikes the boundary
2. The properties of the 2 media
Snell's Law
- Describes the mathematical relationship between the angle of incidence and the angle of refraction
- Equation: n1(θ1) = n2(θ2)
- N is the index of refraction, 1 is the 1st medium, 2 is the 2nd medium, θ1 is the angle of incidence, θ2 is the angle of refraction
Fiber Optics
- Fiber optic cables transmit information in pulses of light (similar to Morse code)
- Used in telecommunications, computer networking, by mechanics, and doctors
Virtual Image
- Form from diverging light rays
- Appear on the same side of the lens as the object
When light moves from air to water, it bends toward the normal, so _ . If light moves from water to air, _ .
θ1 > θ2
θ1 < θ2
Total Internal Reflection
- Occurs when all light is reflected, and there is no refracted ray
- This can only occur when light travels from a higher index of refraction to a lower index of refraction
Lens
A piece of transparent material, such as glass or plastic, that is used to focus light and form an image
Real Images
- Form from converging light rays
- Appear on the opposite side of the lens as the object
- Can be projected onto a screen