Light

Light

Review…

• We already know that each color of light has its own wavelength & frequency.

Refraction…

• Each color refracts at a different angle.

Heinrich Hertz

• Proved the theory that violet light contains more energy than red light.

Heinrich Hertz’s Experiment

• When red light was shined upon the plate, few particles were emitted from the plate.

Incandescent Light• The bottom line…. The filaments in these

bulbs get so hot they glow & produce light.• Details…. The filament is made of a metal

called tungsten. When turned on, the electrons in the filament vibrate very quickly, creating heat. It creates so much heat that it begins to glow. A toaster works the same way!

Fluorescent

How it works:

• There is a tube, filled with low-pressure gas.• There are electrodes at each end of the tube.• Electricity passes from one electrode to the

other, exciting the gas as the electricity passes through it.

• The gas glows, but gives off UV light.• The phosphorus coating on the tube absorbs

the UV and converts it into visible light.

Advantages

Incandescent• Gives off full spectrum (Roy

G. Biv)• Feels “homey.”

Fluorescent• Very energy efficient• Cheaper on the energy bill

Disadvantages

Incandescent• 90% of energy is lost as heat• Expensive energy bill

Fluorescent• Can cause eye fatigue• Can lead to mental

distraction• Harsh colors (not homey or

cozy feeling)