Optics
Diffraction of light
Observe single-slit Fraunhofer diffraction built from Huygens sources, and verify the minima condition plus the scaling of the central maximum, .
⚠ If you reproduce this with a laser pointer, never aim the beam at eyes or reflective surfaces; diffraction patterns are best projected on a diffuse screen.
Equipment
- Slit plane with secondary Huygens sources; intensity screen
- Sliders “Bước sóng λ”, “Khe rộng a”, “Khoảng màn L” (wavelength, slit width, screen distance)
- “Đặt lại tham số” (reset parameters) button
Procedure
Watch the pattern form
Keep default settings and watch the Huygens wavelets from the slit interfere on the screen: a bright central maximum flanked by symmetric minima and weaker side lobes. Read the intensity profile and locate the first minimum.
Narrow the slit
Reduce the slit-width slider a and watch the pattern spread — counterintuitively, a narrower slit diffracts more. Read the angular position of the first minimum and check it against ; halving a should double the width .
Change λ and L
Sweep the wavelength slider and then the screen distance L: the whole pattern scales linearly with both, . Pick one setting, compute the slit width from the measured central width via , and verify it against the slider value.