A 100 W incandescent light bulb has a cylindrical tungsten filament 30.0 cm long, 0.40 mm in diameter, and with an emissivity of 0.26. (a) What is the temperature of the filament? (b) For what wave- length does the spectral emittance of the bulb peak? (c) Incandescent light bulbs are not very efficient sources of visible light. Explain why this is so.

Assume the intensity of solar radiation incident on the cloud tops of the Earth is 1 677 W/m². (a) Taking the average Earth-Sun separation to be 1.496 x 10¹1 m, calculate the total power radiated by the Sun. 4.905E26 x Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. W (b) Determine the maximum value of the electric field in the sunlight at the Earth's location. kv/m (c) Determine the maximum value of the magnetic field in the sunlight at the Earth's location. μT

The next four questions use this description.  Our Sun has a peak emission wavelength of about 500 nm and a radius of about 700,000 km. Your dark-adapted eye has a pupil diameter of about 7 mm and can detect light intensity down to about 1.5 x 10-11 W/m2.  Assume the emissivity of the Sun is equal to 1. First, given these numbers, what is the surface temperature of the Sun in Kelvin to 3 significant digits? What is the power output of the Sun in moles of watts?  (in other words, take the number of watts and divide it by Avogadro's number) Assuming that all of the Sun's power is given off as 500 nm photons*, how many photons are given off by the Sun every second? Report your answer to the nearest power of 10 (e.g. if you got 7 x 1024, give your answer as 25).

The figure below depicts spectral reflectance measurements for three different materials:  a green leaf from a healthy plant, a sheet of shiny blue paper, and the palm of a human hand.  The measurements are labeled 1 (black line), 2 (red line), and 3 (blue line).  Match the measurements to the most appropriate material type