Light And Optics

Front 1

Electromagnetic Wave

Back 1

- Oscillating electric charge
- E/B are perpendicular to each other

Front 2

Speed of Light (c)

Back 2

3.0 e8 m/s

All electromagnetic waves travel at the same speed in the same medium

Front 3

Electromagnetic Spectrum

Back 3

Radio - Micro - IR - Visible - UV - Xray - Gamma

Front 4

Photon Energy Equation

Back 4

E = hf = hc/λ

Front 5

Reflection

Back 5

Өi = Өr

Note: this is the angle between the light ray and the normal to the surface!

Front 6

Index of Refraction

Back 6

n = c/v

- Unique for medium, n is always greater than 1, has no units
- Again, note that the angle is between the ray and the normal

Front 7

Angle of Refraction

Back 7

n₁sin₁ = n₂sin₂

- Where 1 is incidence, 2 is refracted

Front 8

Important Implications of Snell's Law

Back 8

- If n₂ > n₁, then ϴ₂ < ϴ₁. Ray bends TOWARD normal
- If n₂ < n₁, then ϴ₂ > ϴ₁. Ray bends AWAY from the normal

Front 9

Total Internal Reflection

Back 9

sinϴ crit = n₂/n₁

- If a ray exceeds a "critical angle", namely if n₁ > n₂, there will be no refracted ray
- There is ONLY a critical angle if n₂ < n₁.

Front 10

Diffraction

Back 10

- When waves don't travel in a single direction
- Example: wave encounters some sort of interference, like a rock
- Redistribution of waves intensity so that it spreads out

Front 11

Polarization

Back 11

- Light that has been restricted
- Normally EM waves vibrate in all planes

Front 12

Dispersion

Back 12

- Variation in frequencies for different wave speeds
- Example: prism, colors of light have different refraction angles, and come out at different angles
- Violet light has a higher frequency, it bends more
- Red has less frequency, bends less

Front 13

Plane Mirror

Back 13

- Ordinary flat mirror
- Produces image that is the same size, upright, virtual

Front 14

Concave Mirror

Back 14

- Has a focal point in front of the mirror
- Positive (+) f

Front 15

Focal Point

Back 15

- Always ½ from C (center of mirror)

Front 16

Radius of Curvature

Back 16

- Distance between C and the actual mirror

Front 17

Focal Point

Back 17

f = ½r

- Distance from mirror to the focal length

Front 18

Real Image (Mirror)

Back 18

- "real images" are inverted
(+i), (-m)

Front 19

Virtual Image (Mirror)

Back 19

- "virtual" images are upright
- By definition: +m (bigger)
- By definition: -i (image is not real).

Virtual images differ from real images in the sense that the image APPEARS where light rays have converged (but they don't actually appear where it should).

Front 20

Mirror and Lens Equation

Back 20

1/o + 1/i = 1/f

- Where o = object distance from mirror (always positive)
- Where i = Image distance from mirror
- Where f = focal length

Front 21

Magnification

Back 21

m = -i/o

- Tells us how many times bigger the produced image will be compared to the original
- if m is (+), upright, virtual
- if m is (-), inverted, real

Front 22

Converging Lens

Back 22

- Thicker, retract light toward focal point on the other side of the lens
+ F

Front 23

Diverging Lens

Back 23

- Thinner in the middle, direct light away from the imaginable focal length in front of the lens
- Equivalent to concave
- Have a (-) f

Front 24

Real Image (Lens)

Back 24

- Have positive i (image is on other side of lens)
- Have negative m (inverted)

Front 25

Virtual Image (Lens)

Back 25

- Have negative i (image on same side as lens)
- have positive m (image is upright)

Front 26

Lens Power

Back 26

P = 1/f

Front 27

Farsightedness

Back 27

- Can't see close up
- Converging lenses with +P
- Image is behind the retina until correction with lens

Front 28

Nearsightedness

Back 28

- Can't see far away
- Diverging lens with -P
- Image is in front of the retina until correction