Chapter 25, Problem 56RPP

BIO Amazing honeybees The survival of a bee colony depends on the ability of bee scouts to locate food and to convey that information to the hive. After finding a promising food source, a honeybee scout returns to the hive and uses a waggle dance to tell its worker sisters the direction and distance to the food.

Recall that light coming directly from the Sun is unpolarized Bees use the direction of the Sun as a reference for their travel In the hive, the scout bee's waggle dance is in the shape of a flat figure eight (Figure 25.28). The upward direction in the vertical hive represents the direction toward the Sun. The middle line of the scout’s figure eight points in the direction of the food relative to the direction of the Sun. Thus a $50°$ middle waggle dance to the right of the vertical in the hive would indicate a food source outside that is $50°$ to the right of the direction toward the Sun The distance to the food depends on the length of time the scout takes while wiggling her tail and wings through this middle of the figure eight. The other bees know the direction to the food even if the Sun is behind a cloud—they can detect the degree of polarization in other open parts of the sky and deduce the angle to the Sun from that position, and they learned from the scout the angle from the Sun’s direction to the food.

Incandescent lightbulbs—soon to disappear Australia, Canada, New Zealand, and the European Union started phasing out incandescent lightbulbs in 2009. The United States phased them out in 2014. These bulbs have provided light for the world for more than 90 years What’s the problem?

Incandescent lightbulbs produce light when electrons (electric current) move through the filament and collide with tungsten atoms and ions in the filament, causing them to vibrate violently Accelerating charged particles emit electromagnetic radiation. This is true for vibrating and accelerating particles in the filament, in your skin, and on the Sun The $\text{35 °C}$ skin of a person emits most of its radiation in the low-frequency, long-wavelength infrared— sometimes called thermal radiation At $\text{2500 °C}$, the filament of an incandescent lightbulb emits most of its radiation as higher frequency infrared radiation and just $10\%$ as visible light (very inefficient if the goal is to produce light). At $\text{6000 °C}$, the Sun emits about $45\%$ in the infrared range and $40\%$ in the visible light range.

Banning incandescent bulbs will reduce energy usage According to the Department of Energy, about ${\text{10}}^{\text{18}}\text{J}$ of electric energy is used each year in the United States for household lighting Compact fluorescent lightbulbs (CFLs) and light-emitting diode (LED) bulbs use about one-fourth the energy of incandescent bulbs Switching to CFLs and LEDs would also reduce greenhouse gas emissions by reducing the need for power produced by coal-burning electric power plants

What is the rate of visible light emission from a 100-W incandescent lightbulb?

a. 10 W

b. 20 W

c. 50 W

d. 100 W

e. Not enough information to make a determination