Physics 3

Question 1

Parallax

Answer 1

the apparent shift in position of an object when its viewed from various angles

Question 2

Luminous Body

Answer 2

emits light waves ex. sun

Question 3

Illuminated Body

Answer 3

reflect light waves ex moon

Question 4

Luminous Flux ( italicized P)

Answer 4

rate at which light is emitted from a source (unit lumens Lm)

Question 5

Illuminance ( E)

Answer 5

the illuminance of a surface (Lm/m^2)

Question 6

Candela

Answer 6

luminous intensity

Question 7

Transparency

Answer 7

transmits light waves and you CAN see through it. ex glass, water, air

Question 8

Translucent

Answer 8

transmits light but you CANNOT see through it. ex. lamp shade, shower doors, skin shower curtains

Question 9

Opaque

Answer 9

light cannot pass through it (reflects off of or absorbs) ex. wall, books

Question 10

Galileo (1564- 1642)

Answer 10

Made the first serious attompt to measure the speed of light
-took 2 lanterns about 1km apart and “flashed” each other (one lantern was flashed and the lantern flashed back upon seeing the first lantern)
- Galileo hoped to use the time interval btwn the flash of each lantern and the distance btwn lanterns, to calculate the speed of light

Question 11

What was Galileo’s problem

Answer 11

• Problem: it didn’t work. said that the speed of light was infinite and couldn’t be calculated
• Not an accurate method: Human reaction time is too slow. Reaction time took longer than the time for light to travel this distance.
  Measurement of time was not accurate enough

Question 12

Olaus Roemer (1644 - 1710)

Answer 12

Danish astronomer
- tried to predict the eclipses of Jupiter’s moon (abt Jupiter)
-surprised to find out that the period of the eclipse, as he measured for one of the moons, was different at different times of tear.
- concluded that light has a finite speed (and that it was constant) and that the reason eclipse periods appeared to ching was bc:

Question 13

Olaus Roemer concluded the reason eclipse periods appeared to change is bc:

Answer 13

• depending on the Earths distance from Jupiter, light needs more or less time to reach Earth from Jupiter
• difference between the two measured time periods is equal to the time it takes light to travel a distance appoximately equal to the diameter of the earths orbit

Question 14

What was Olaus’ problem

Answer 14

Roemer didnt know how large the diameter of the Earths orbit was

Question 15

Christian Huygens (approx same time as Roemer)

Answer 15

Dutch mathmatican/scientist
- Managed to figure ont the diameter of Earths orbit
- Used his data and Roemers data to calculate the speed of light
- difference between shortest and longest period Δt = 22 min (1320 s)

Question 16

diameter of earths orbit

Answer 16

3x10^11 m/s

Question 17

d= v/t