Where does this come from, and can I check it?

A 405 nanometre laser and a thin cover layer let one layer of a disc hold 25 gigabytes, five times a DVD. The figure is taken from Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a technology fact?

Yes. It sits on the Technology shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

What else can I read about it?

The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

Blu-ray uses a violet laser to pack in data

A 405 nanometre laser and a thin cover layer let one layer of a disc hold 25 gigabytes, five times a DVD Shorter wavelength light can be focused to a smaller spot, so Blu-ray reads marks roughly half the size of a DVD's. The data layer sits just 0.1 millimetres below the surface under a hard coat, which allows a lens of high numerical aperture. The format beat Toshiba's HD DVD in 2008 after several studios chose it. It sits in Mondo's technology collection, one of 200 facts that each trace back to the reference below.

Where this comes from

Britannica

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

Go further

Technology trivia Movies & Television trivia

More facts like this

Reed-Solomon codes keep scratched discs playableIrving Reed and Gustave Solomon published the maths in 1960, and it now protects CDs, QR codes and deep space links Lidar measures distance by timing a light pulseA short laser flash bounces off a surface, and the return delay gives range to within a few centimetres 3D printing was patented by Chuck Hull in 1984 using stereolithographyUltraviolet lasers solidifying liquid photopolymer resin layer by layer created 3D objects Magnetic tape still archives most large data setsLinear Tape-Open cartridges stay offline and cost far less per terabyte than spinning disks Stored files can rot without anyone touching themMagnetic, optical and flash media all lose data slowly, and a checksum is often the only sign that anything changed The first commercial hard disk stored five megabytes of dataThe IBM 350 disk storage unit used fifty magnetic platters each measuring twenty inches across

Tags: optical-discs, storage, lasers

Blu-ray uses a violet laser to pack in data: the short answers

Where does this come from, and can I check it?: A 405 nanometre laser and a thin cover layer let one layer of a disc hold 25 gigabytes, five times a DVD. The figure is taken from Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a technology fact?: Yes. It sits on the Technology shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.