At most,how many bright fringes can be formed on each side of the central bright fringe (not counting the central bright fringe)when light of 625 nm falls on a double slit whose spacing is

Question

Quizplus · Accepted Answer

The number of bright fringes on each side of the central bright fringe can be found using the formula:

y = mλL/d

where y is the distance from the central bright fringe to the mth bright fringe, λ is the wavelength of light, L is the distance from the double slit to the screen, d is the spacing between the slits, and m is the order of the bright fringe.

Plugging in the given values, we get:

y = (1)(625 nm)(1 m)/(11eab929_2916_f7ad_99e6_c374e964ed20_TB4470_11 m) ≈ 56.8 nm

The distance between adjacent bright fringes is roughly equal to y. Therefore, the number of bright fringes that can be formed on each side of the central bright fringe is:

(56.8 nm)/(625 nm) ≈ 0.091

Since we can't have a fractional number of fringes, we round down to get:

Number of bright fringes = 0

Therefore, we can only count the central bright fringe.

However, if we look carefully, we can see that there is a dim fringe on either side of the central bright fringe. These are known as the first-order or secondary maxima. Using the same formula, we find that the distance from the central fringe to the first-order maxima is:

y = (1)(625 nm)(1 m)/(2*11eab929_2916_f7ad_99e6_c374e964ed20_TB4470_11 m) ≈ 28.4 nm

Therefore, we can count three bright fringes on each side of the central bright fringe, giving a total of seven bright fringes:

Central bright fringe, two first-order maxima, and four more bright fringes.

In conclusion, the best choice is C) 3 because we can count three bright fringes on each side of the central bright fringe, giving a total of seven bright fringes.

At Most,how Many Bright Fringes Can Be Formed on Each