Light CalculationsLight Calculations

Find the v of each of these.Material nVacuum 1.0000Air 1.0003Ice 1.31Water 1.333Ethyl Alcohol 1.36Crown Glass 1.52Zircon 1.923Diamond 2.417

n = c/v

v3.00 E8 m/s3.00 E8 m/s2.29 E8 m/s2.25 E8 m/s2.21 E8 m/s1.97 E8 m/s1.56 E8 m/s1.24 E8 m/s

Calculating Ray DiagramsCalculating Ray Diagrams

350

300

Air

n =

ni sinΘi =nrsinΘr

?

Θi

Θr

ni = 1.0003

1.0003 x sin35 = nr sin30

1.0003 x 0.574 = nr 0.5

0.5 0.5

nr = 1.15

Water

Air

200

Θ =

Calculating Ray DiagramsCalculating Ray Diagramsni sinΘi =nrsinΘr

nr =

Θi

Θr

ni = 1.333

1.333 x sin20 = 1.0003 sin Θ

1.333 x 0.342 = 1.0003 sin Θ 1.0003 1.0003

sinΘ = 0.456

Θ = 27.1 o

1.0003

To get Θ alone you need to multiply the opposite

side by sin -1

Θ = sin -1 0.456

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PracticePractice

• How long does it take light to travel 123456789 m?How long does it take light to travel 123456789 m?

• How far will light travel in 12 seconds?How far will light travel in 12 seconds?

• How fast (m/s) does a beam of light travel if it How fast (m/s) does a beam of light travel if it takes 5 s to travel 1.50 takes 5 s to travel 1.50 E6 E6 km?km?

d = ?t = 12s v = d/t

v = 3E8 m/sd = vt3E8 m/s x 12s = 3.60 E9 m

d = 123456789 mt = ? v = 3E8 m/s t =

123456789m / 3E8 m/s = 4.12 E-1 sd/v

t = 5sd = 1.50 E6 km

v = ? v = d/t1.50 E9 m

=1.50 E9 m/5 sv = 3.00 E8 m/s

Θi = ?Air

Glass

Θr =100

Θi =450 water

n = ?What

medium Θr =230

Θi = 48.70 n = ?What medium?

ice

Θr = 350

Θi = 780

air

zircon

Θr = ?θ = 30.6 O

Θi = ?Air

Glass

Θr =100

1.0003 x sinθ = 1.52 sin10

sinθ = 0.264/1.0003

θ = sin-10.264θ = 15.3 0

Θi =450 water

n = ?What

medium Θr =230

1.333 x sin45 = n sin23

0.943/.391 = n

n = 2.41 diamond

Θi = 48.70 n = ?What medium?

ice

Θr = 350

n x sin48.7 = 1.31sin35

n = 0.751/0.751

n = 1.00 vacuum/air

Θi = 780

air

zircon

Θr = ?

1.0003 x sin78 = 1.923 sinθ

= 0.978/1.923 = sinθ

θ = sin-10.509

θ = 30.6 O

θ = 30.6 O