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RRB NTPC Graduate Tier 1 2025 Shift-1 📅 09 Jun, 2025

What are the wavelength and type of the laser used in a standard CD-ROM drive?

A
400 nm; blue laser
B
780 nm; infrared laser
C
650 nm; red laser
D
850 nm; near-infrared laser
Result Summary
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APEDIA

RRB NTPC Graduate Tier 1
2025 • 09 Jun, 2025 • Shift-1
What are the wavelength and type of the laser used in a standard CD-ROM drive?
Correct Answer
780 nm; infrared laser
Optical Storage Mechanics: Compact Disc Read-Only Memory (CD-ROM) drives utilize focused light beams to read microscopic pits and lands encoded on the reflectiv......
💡 Analysis & Explanation
Optical Storage Mechanics
Compact Disc Read-Only Memory (CD-ROM) drives utilize focused light beams to read microscopic pits and lands encoded on the reflective surface of the disc.
Laser Specifications
Standard CD technology historically and technically relies on a specific semiconductor laser diode. This laser operates within the infrared spectrum at a standardized wavelength of 780 nanometers, which perfectly aligns with the physical track pitch of CDs.
Conclusion
A standard CD-ROM drive operates using a 780 nm infrared laser.