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Home Page of Peggy E. Schweiger

Illumination Sample Problems

  1. A student’s desk top is 2.5 m from a 1750 lm lamp. What is the illumination of the desk top?
  2. A surface is illuminated by a 32 cd bulb. What is the bulb’s luminous flux? If the bulb is located 2 m from the surface, what is the surface’s illumination?
  3. A 64 cd source is 3 m above the surface of a desk. What is the illumination of the surface?
  4. A photometer is used to compare the illuminationof two bulbs. It is positioned until it is equally illuminated by each bulb. If it is 75 cm from a 50 cd source, how far is it from a 65 cd source?
  5. A photometer is equally illuminated when it is 60 cm from a 40 cd source and 40 cm from an unknown source. What is the intensity of the unknown source?
  6. A lamp is moved from 30 cm to 90 cm above a book. How much greater was the illumination before it was moved?
  7. Compare the illumination of a surface by a bulb when it is 1.5 m away to when it is 2.5 m away.

Diffraction Sample Problems

  1. A diffraction pattern is formed using red light. A first order line is formed 0.221 m to the left of the central bright spot. The slits are separated by 1.9 x 10-6 m. If it is 0.6 m to the first order line from the slits, what is the wavelength of light in meters? In nanometers? In angstroms?
  2. Slits separated by 0.02 cm are used to form a first order line on a screen 100 cm away. The lines are formed 0.295 cm from the central bright spot. What is the light’s wavelength and frequency?
  3. A slit 0.0001 m wide is located 1 m from a screen and used to form a first order dark band 0.006 m from the central bright band. What is the light’s frequency?
  4. 5000 A light forms a diffraction pattern on a screen 50 cm away. The slit is 0.02 cm wide. What is the distance to the first order dark band?
  5. A diffraction grating has 500 lines/mm. What is its slit width?
  6. If this diffraction grating is used to form the diffraction pattern in number 2, what would the distance to the second order dark band be?