Question

Laser beam is used:

• A. In magnetic tape recording
• B. In DVD disc recording
• C. In analog sound recording in CD
• D. In analog sound reproduction from CD

Hint:

Optical storage devices use different laser wavelengths: - CDs use an infrared laser ($780\text{ nm}$). - DVDs use a red laser ($650\text{ nm}$). - Blu-ray discs use a blue-violet laser ($405\text{ nm}$), which has a much shorter wavelength, allowing it to write data at a much higher density.

Answer 1

The Correct Option is B

Step 1: Understanding Optical Storage Technology:
Compact Discs (CDs) and Digital Versatile Discs (DVDs) are optical storage media. They store data as microscopic physical structures (pits and lands) on a reflective layer.

Step 2: Evaluating the Options:

• Magnetic tape recording (A): Uses an electromagnetic write head to align magnetic particles on a tape, and does not use lasers.
• Analog CD recording/reproduction (C & D): This is technically incorrect because CDs are strictly digital media; they do not store or reproduce analog signals directly.
• DVD disc recording (B): A highly focused, coherent laser beam (typically a red laser at a wavelength of $650\text{ nm}$) is used to write digital data by physically burning pits into the organic dye layer of the DVD disc.

Step 3: Conclusion:
Therefore, the laser beam is used in DVD disc recording, making option (B) correct.