Chapter 33. Light and Illumination

Light and the Electromagnetic Spectrum

33-1. An infrared spectrophotometer scans the wavelengths from 1 to 16 m. Express these range in terms of the frequencies of the infrared rays. Range of frequencies: 1.88 x 1013 Hz to 30 x 1013 Hz

33-2. What is the frequency of violet light of wavelength 410 nm? f = 7.32 x 1014 Hz

33-3. A microwave radiator used in measuring automobile speeds emits radiation of frequency 1.2 x 109 Hz. What is the wavelength?  = 250 mm

33-4. What is the range of frequencies for visible light? ( Range of : 700 nm to 400 nm ) Range of frequencies: 4.29 x 1014 Hz to 7.50 x 1014 Hz

33-5. If Plank’s constant h is equal to …ver más…

An 8½ x 11 cm sheet of metal is illuminated by a source of light located 1.3 m directly above it. What is the luminous flux falling on the metal if the source has an intensity of 200 cd. What is the total luminous flux emitted by the light source? A = (0.085 m)(0.11 m); A = 9.35 x 10-3 m2 F = I = (200 cd)(5.53 x 10-3 sr); F = 1.11 lm Total Flux = 4I = 4(200 cd); Total Flux = 2510 lm

33-22. A 40-W monochromatic source of yellow-green light (555 nm) illuminates a 0.5-m2 surface at a distance of 1.0 m. What is the luminous intensity of the source and how many lumens fall on the surface? F = (680 lm/W)(40 W) = 27,200 lm; I = 54,400 cd
33-23. What is the illumination produced by a 200-cd source on a small surface 4.0 m away? E = 12.5 lx

33-24. A lamp 2 m from a small surface produces an illumination of 100 lx on the surface. What is the intensity of the source?
I = ER2 = (100 lx)(2 m)2; I = 400 cd

33-25. A table top 1 m wide and 2 m long is located 4.0 m from a lamp. If 40 lm of flux fall on this surface, what is the illumination E of the surface? E = 20 lx

33-26. What should be the location of the lamp in Problem 33-25 in order to produce twice the illumination? ( Illumination varies inversely with square of distance.)
E1R12 = E2R22 = (2E1)R22; R2 = 2.83 m

*33-27. A point source of light is placed at the center of a sphere 70 mm in diameter. A hole is cut in