Typical infrared wavelength range

Steps:

• Convert options to micrometers: A = 5 μm, B = 0.5 μm, C = 2 μm, D = 0.002 μm.
• Recall infrared spans 0.7–1000 μm, beyond visible light (0.4–0.7 μm).
• For optic fiber lasers, near- to mid-IR wavelengths minimize silica absorption; 5 μm fits mid-IR used in some transmission systems.
• Eliminate non-IR options and select A as representative typical value.

Why A is correct:

• 5 × 10^{-6} m equals 5 μm, within the standard infrared range (0.7–1000 μm) per electromagnetic spectrum definitions.

Why the others are wrong:

• B: 0.5 μm is visible light (violet), shorter than IR threshold.
• C: 2 μm is IR but less typical for broad IR examples than 5 μm.
• D: 2 × 10^{-9} m (2 nm) is ultraviolet, far below IR.

Final answer: A