問56
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次の記憶媒体のうち, 記録容量が最も大きいものはどれか。ここで, 記憶媒体の直径は12cmとする。
平成28年度 秋期 ITパスポート試験 問56
テクノロジ系コンピュータ構成要素 › メモリ
This question's explanation and your answers so far.
解説
問 56
- ア
正解 For a 12 cm optical disc, the recording capacity depends on the wavelength of the laser used to read and write the pits (the smallest units of recording): the shorter the wavelength, the smaller the pits can be and the higher the recording density, so the capacity grows. Choice ア, BD-R (Blu-ray Disc), uses a blue-violet laser (wavelength about 405 nm), giving it the highest density, and it can record about 25 GB per layer. This far exceeds CD-R (about 700 MB) and DVD-R / DVD-RAM (about 4.7 GB per single-sided single layer), so among the four the one with the largest recording capacity is ア.
Incorrectイ
CD-R uses an infrared laser (wavelength about 780 nm) and is the oldest generation of optical disc; its recording capacity is about 700 MB (0.7 GB), the smallest among the choices. It falls far short of BD and DVD, so it is not the largest.
Incorrectウ
DVD-R uses a red laser (wavelength about 650 nm) and holds about 4.7 GB per single-sided single layer. It is larger than CD-R but does not reach BD-R's roughly 25 GB, so it is not the largest.
Incorrectエ
DVD-RAM is a rewritable DVD, but its recording capacity is about the same as DVD-R, roughly 4.7 GB per single-sided single layer. It does not reach BD-R's roughly 25 GB, so it is not the largest.
ここがポイント
- An optical disc's recording capacity is determined by its generation (laser wavelength); the capacities rank CD (about 700 MB) < DVD (about 4.7 GB) < BD (about 25 GB). BD, which uses the shortest-wavelength blue-violet laser, has the highest density and the largest capacity.
- Note that same-generation DVD-R and DVD-RAM have almost the same recording capacity, about 4.7 GB, even though their recording methods differ (write-once versus rewritable).
用語