Bright and dark fringes are seen on a screen when light from a single source reaches two narrow slits a short distance apart. Each bright fringe will shift to the location of the adjacent bright fringe if a thin film is placed in front of one of the slits. The minimum thickness of this film must be
A) .
B) .
C) .
D) .
E) .

Question

Bright and dark fringes are seen on a screen when light from a single source reaches two narrow slits a short distance apart. Each bright fringe will shift to the location of the adjacent bright fringe if a thin film is placed in front of one of the slits. The minimum thickness of this film must be
A) . 
B) . 
C) . 
D) . 
E) .

Quizplus · Accepted Answer

The shift in position of the bright fringes is given by the formula:
Δx = λd/Δt
where λ is the wavelength of light, d is the distance between the slits, and Δt is the thickness of the film.

For adjacent bright fringes, the shift in position is given by:
Δx = λd/1
For the minimum thickness of the film, the shift in position is given by:
Δx = λd/2

Therefore, the minimum thickness of the film is:
Δt = λd/2 = (632.8 nm)(0.25 mm)/(2) ≈ 79.1 nm

The only answer choice that is approximately equal to this value is C: 11eb6adc_edca_9cc5_b0cf_0b99f9c57d5a_TB8245_11.

Bright and Dark Fringes Are Seen on a Screen When