Question

Use first question to answer other 2. I need help understanding how to get to the answers.

1) Light from two lasers is incident on an opaque barrier with a single slit of width 3.0 x 10-4 m. One laser emits light of wavelength 440 nm and the other is 660 nm. A screen to view the light intensity pattern is 2.0 m behind the barrier. What is the distance from the center of the pattern to the nearest completely dark spot (dark for both colors)? (1 cm = 0.01 m) a) 1.68 cm b) 1.48 cm c) 1.28 cm d) 1.08 cm e) 0.88 cm

(I know how to do #1, so I don't need work for this one. The answer is e)

2) The 440 nm laser is now switched off and a 2nd slit of the same width is made in the barrier. The centers of the slits are 6.0 x 10-4 m apart. Approximately how many smaller bright spots are now observable within the central bright region? a) 4 b) 6 c) 8 d) 10 e) 12 7.

(answer is a, but I got b)

3) The 2-slit experiment from the question above is now repeated with the 440 nm laser (the 660 nm laser is switched off). Approximately how many smaller bright spots are observable within the central bright region? a) 4 b) 6 c) 8 d) 10 e) 12

(answer is a)

Answer 1

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since final answer does not depend on wavelength of it will be same for both question