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## PowerPoint Slideshow about ' Waves, Light & Quanta' - wallace-hawkins

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### Circumference of the earth

### Camera obscura

### Rays

### The nature of light

### Rays

### Reflection

### Reflection at a curved surface

### Concave mirror

### Lenses and refraction

### Fermat’s principle of least time

### Fermat’s principle of least time

### Snell’s law of refraction

### The nature of light

(Tropic of Cancer)

Eratosthenes of Cyrene (276-195 BC)

- 5000 stadia ~ 5000 x 180m = 900 km

- α = β ~ 1/50 circle

Reinerus Gemma-Frisius, Leuven

de radio astronomica et geometrica, 1545

- solar eclipse, 24 Jan 1544

b

x

x

0

L

S

S

- light travels in straight lines

- shortest distance between two points

B

C

A

P

P

light travels in straight lines

light travels between two points by the shortest distance

P=S

- equal angles:

b

x

x

0

L

S

S

- light travels in straight lines

- shortest distance between two points

B

C

A

P

P

P

b

a

P=S

- equal angles:

b

P

x

x

0

L

S

S

- light travels in straight lines

- shortest distance between two points

P

P

S

P

P=S

- equal angles:

- light travels in straight lines

- shortest distance between two points

- suppose we design a surface so that all routes are the same length…?

S

P

P=S

- equal angles:

- light travels in straight lines

- shortest distance between two points

f

R

- equal times to focus

Nicholas of Rouen

Ibn al-Haytham ‘Alhazen’

(965-1039)

Tommaso da Modena (1325-1379)

Chiesa San Nicolò, Treviso

b

x

x

0

L

S

S

B

C

A

P

P

- refraction at a plane surface

Pierre de Fermat (1601-1665)

b

x

x

0

L

Pierre de Fermat (1601-1665)

S

S

- light rays follow the path of least time between two points

P

P

- refraction at a plane surface

b

x

x

0

L

Willebrord Snel van Royen

(Leiden, 1580-1626)

S

S

- light rays follow the path of least time between two points

P

P

- refraction at a plane surface

light travels in straight lines

light travels between two points by the shortest distance

light travels between two points by the quickest route (least time)

light travels between two points by the route for which the time taken is a stationary value

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