He-Ne Laser
Helium-neon lasers are used in engineering laboratories, in robot vision systems, and even in the barcode readers found in supermarket checkout counters. A certain laser has a power output of 3 mW and produces light of wavelength λ = 632.8 nm. The lowercase Greek character lambda (λ).The lowercase Greek character lambda (λ) is a conventional symbol used for wavelength; Appendix A summarizes the names and symbols of other Greek letters. (a) Convert the power rating to horsepower. (b) Convert the wavelength to inches.
Approach
Referring to Table 3.3,
| Name Symbol Multiplicative Factor | ||
| tera | T | 1,000,000,000,000 = 10^{12} |
| giga | G | 1,000,000,000 = 10^9 |
| mega | M | 1,000,000 = 10^6 |
| kilo | k | 1000 = 10^3 |
| hecto | h | 100 = 10^2 |
| deca | da | 10 = 10^1 |
| deci | d | 0.1 = 10^{-1} |
| centi | c | 0.01 = 10^{-2} |
| milli | m | 0.001 = 10^{-2} |
| micro | μ | 0.000,001 = 10^{-6} |
| nano | n | 0.000,000,001 = 10^{-9} |
| pico | p | 0.000,000,000,001 = 10^{-12} |
the power dimension mW refers to a milliwatt or 10^{−3} W, and nm denotes a billionth of a meter (10^{−9 }m). The conversion factors for power and length are listed in Table 3.6
Table 3.6 Conversion Factors between Certain Quantities in the USCS and SI
| Quantity | Conversion |
| Length | 1 in. = 25.4 mm |
| 1 in. = 0.0254 m | |
| 1 ft = 0.3048 m | |
| 1 mi = 1.609 km | |
| 1 mm = 3.9370 ×10^{-2} in. | |
| 1 m = 39.37 in. | |
| 1 m = 3.2808 ft | |
| 1 km = 0.6214 mi | |
| Area | 1 in^2 = 645.16 mm^2 |
| 1 ft^2 = 9.2903 × 10^{-2} m^2 | |
| 1 mm^2 = 1.5500 × 10^{-3 }in^2 | |
| 1 m^2 = 10.7639 ft^2 | |
| Volume | 1 ft^3 = 2.832 × 10^{-2} m^3 |
| 1 ft^3 = 28.32 L | |
| 1 gal = 3.7854 × 10^{-3} m^3 | |
| 1 gal = 3.7854 L | |
| 1 m^3 = 35.32 ft^3 | |
| 1 L = 3.532 × 10^{-2} ft^3 | |
| 1 m^3 = 264.2 gal | |
| 1 L = 0.2642 gal | |
| Mass | 1 slug = 14.5939 kg |
| 1 lbm = 0.45359 kg | |
| 1 kg = 6.8522 × 10^{-2} slugs | |
| 1 kg = 2.2046 lbm | |
| Force | 1 lb = 4.4482 N |
| 1 N = 0.22481 lb | |
| Pressure or stress | 1 psi = 6895 Pa |
| 1 psi = 6.895 kPa | |
| 1 Pa = 1.450 × 10^{-4 }psi | |
| 1 kPa = 0.1450 psi | |
| Work, energy, or heat | 1 ft · lb = 1.356 J |
| 1 Btu = 1055 J | |
| 1 J = 0.7376 ft · lb | |
| 1 J = 9.478 × 10^{-4} Btu | |
| Power | 1 (ft · lb)/s = 1.356 W |
| 1 hp = 0.7457 kW | |
| 1 W = 0.7376 (ft · lb)/s | |
| 1 kW = 1.341 hp |
as 1 kW = 1.341 hp and 1 m = 39.37 in.
