Home Page of Peggy E. Schweiger

### Illumination Sample Problems

- A student’s desk top is 2.5 m from a 1750 lm lamp. What is the illumination of the desk top?
- 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?
- A 64 cd source is 3 m above the surface of a desk. What is the illumination of the surface?
- 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?
- 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?
- A lamp is moved from 30 cm to 90 cm above a book. How much greater was the illumination before it was moved?
- 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

- 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?
- 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?
- 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?
- 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?
- A diffraction grating has 500 lines/mm. What is its slit width?
- 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?