Interferensi Lapisan Tipis
A soap bubble is colourless — so why the swirling rainbows?
- Soap and water are clear, yet a bubble shimmers with swirling colours.
- A thin film of oil on a wet road does the same.
- The colours come from light reflecting off both surfaces of the thin film and interfering.
- It is interference again — this time from a film only a wavelength or two thick.
Two reflections interfere
- When light hits a thin film, part reflects off the top surface and part off the bottom.
- The two reflected waves travel slightly different distances, then overlap and interfere.
- Depending on the film's thickness and the light's wavelength, they add or cancel.
- The result is bright or dark for each colour, giving the shimmering hues.
Warna gelembung sabun berasal dari:
Pantulan dari permukaan atas dan bawah berinterferensi, menghasilkan warna.
Why the colours change
- The extra path in the film is set by its thickness, so different thicknesses favour different colours.
- As a bubble's wall thins and swirls, the thickness changes and so do the colours.
- One wavelength cancels while another adds, so white light splits into shifting hues.
- Where the film is thinnest (about to pop), it can look black — all colours cancel.
Sifat apa dari lapisan yang menentukan warna mana yang bertambah atau meniadakan?
Ketebalan lapisan menetapkan lintasan ekstra, sehingga menentukan interferensi untuk setiap warna.
Pilih semua pernyataan benar tentang interferensi lapisan tipis.
Warna lapisan tipis berasal dari interferensi dua permukaan yang ditentukan oleh ketebalan, dan memperkuat lapisan anti-pantulan. Tidak ada pigmen terlibat.
Useful thin films
- Anti-reflection coatings on camera lenses and glasses use thin films to cancel reflected light.
- The coating is made exactly the right thickness to make reflections interfere destructively.
- That lets more light through the lens and cuts glare.
- The same physics that colours a bubble makes your glasses reflect less.
Lapisan terang atau gelap?
Lapisan tipis terlihat terang atau gelap tergantung pada bagaimana gelombang pantul bergabung. Urutkan setiap kasus.
Lapisan sabun yang akan pecah bisa terlihat hitam karena:
Saat sangat tipis, dua pantulan saling meniadakan untuk semua warna, sehingga sedikit cahaya terpantul.
Lapisan lensa yang menggunakan lapisan tipis untuk meniadakan cahaya terpantul disebut lapisan anti-pantulan.
Lapisan anti-pantulan membuat pantulan mengalami interferensi destruktif.
The colours of a soap bubble are not pigments — soap is colourless. They come from interference between light reflected off the two surfaces of the film. As the film's thickness changes, which colours cancel and which add changes too, so the colours swirl.
Warna gelembung sabun disebabkan oleh pigmen dalam sabun.
Sabun tidak berwarna; warnanya berasal dari interferensi lapisan tipis.
Why does a soap film sometimes look black just before it bursts?
- The film has thinned to almost nothing, so the path difference is nearly zero — but the top-surface reflection flips by half a wavelength while the bottom one does not, so the two reflections end up out of step and cancel.
- Every visible colour interferes destructively, so little light reflects — it looks dark.
Thin-film interference colours soap bubbles and oil slicks: light reflecting off the film's two surfaces overlaps and interferes. The thickness decides which colours add or cancel, so the hues shift as the film changes. The same effect powers anti-reflection coatings on lenses.