1. Lesson 4 Light Key Concepts
Page 48 yellow lab notebook

2. The area illuminated by a light source increases with the distance of area from the source.

3. The apparent brightness of a light decreases as the distance between the light source and the surface illuminated increases.

4. notes

5. A.
A light with a reflector produces a beam of light that can (because the reflector focuses it) resist spreading or even converge for a distance as it emerges from the reflector.

6. B.
Light from a point source is emitted evenly along all directions throughout the surrounding space.

7. C. Light Sources with reflectors
Ex: flashlights
Produces beam of light that can resist spreading
Can converge for a distance as it emerges from the reflector

8. D. Light from a point source
Ex: bare lightbulb with a filament
Light emitted evenly along all directions throughout the surrounding space

9. Light source – single filament halogen lightbulb
E. Lesson 4
Light source – single filament halogen lightbulb
End of filament is point source

10. F. Photon model for light
Explains why light intensity appears to decrease as light travels away from the lightbulb
visible light radiated (produced)by a source – terms such as brightness, luminance, luminosity, lumens
total energy radiated (released) by a source – terms such as power, watts, radiance
i. released as invisible (ex: infrared) or visible light

11. terms
Wattage: total amount of energy transformed by and released by the lightbulb (both visible and invisible)
Lumens: amount of visible light produced by the lightbulb
Apparent Brightness: not the actual amount of visible light produced; depends on the luminosity of the source and the distance between the source and the detector