In a Young's double-slit experiment, the slits are 1mm apart and are illuminated by laser light of wavelength 681.8nm. The screen is 3.9m away. What is the number of dark fringes per centimetre?
To determine the number of dark fringes per centimeter in a Young's double-slit experiment, we can use the equation:
$$ \text{Number of fringes} = \frac{L \times \lambda}{d} $$
where:
- L is the distance from the slits to the screen,
- λ is the wavelength of the light,
- d is the separation between the slits.
Let's plug in the given values:
L = 3.9m = 390cm
λ = 681.8nm = 0.6818μm = 0.0006818cm
d = 1mm = 0.1cm
Substituting these values into the equation, we have:
$$ \text{Number of fringes} = \frac{390 \times 0.0006818}{0.1} $$
Calculating this gives us the number of dark fringes per centimeter.