Assertion: blue led | /r/MadeOf | rare materials
Facets:
Source sentences:
text: But the color of the light emitted actually depends on the material used in the PN junction (which is why blue LEDs are so expensive - they are made from rare materials).
text: But the color of the light emitted actually depends on the material used in the PN junction (which is why blue LEDs are so expensive - they are made from rare materials).