Cds and dvds act effectively like diffraction gratings when reflecting laser light. holding the disks 1.2 from a wall, you notice that the difference between the two = 1 bright fringes is 98 for the cd and 210 for the dvd when red laser light ( = 650 ) is reflected. how many more lines per mm does a dvd have than a cd?

718 lines per mm is number of line which are more in DVD than CD

Explanation:

we know that fringe width is given as

where

D = 1.2

for CD first order fringe 2yi = 98 cm

y1 = 49 cm = 0.49 m

so,

Number of line on Cd per mm is lines per mm

for DVD

first order fringe 2y2 = 210 cm

y1 = 105 cm = 1.05 m

so,

Number of line on Cd per mm is lines per mm

N_2 -N_1 = 1346.2 - 628.2 = 718 lines per mm

hello there!

your answer is a “generator”

a generator does not create energy but instead it transforms it.

it’s basically a motor working in reverse.

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