The data density of a Blu-ray disk using a 405-nm laser is 1.5x107 bits nm-2. Disks have an outside diameter of 120nm and a hole of 15-nm diameter. How many data bits can be contained on the disk? If a Blu-ray disk can hold 9,400,000 pages of text, how many data bits are needed for a typed page? (hint: determine the area of the disk that is available to hold data. The area inside a circle is given by A=r2, where the radius r is one-half of the diameter.)

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6.4 cm (max) - 25 cm (min)

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.