Answer: C: White light is emitted by blue chip + yellow phosphor.
Answer analysis: When discussing this question, we must first understand the light-emitting principle of white light LED lamp beads. White light LED is not directly emitted by a single color chip, but is mixed by a specific color of light.
Now, let's analyze each option one by one:
A: White light is emitted directly by the white light chip
- This option is incorrect. There is no white light chip that directly emits white light on the market. White light LEDs are usually mixed by other colors of light.
B: White light is emitted by yellow chip + blue phosphor
- This option is also incorrect. Although phosphors can be used to change the color of light emitted by LEDs, white light LEDs do not emit light through a combination of yellow chips and blue phosphors.
C: White light is emitted by blue chip + yellow phosphor
- This option is correct. In white light LEDs, a common practice is to use a blue LED chip as a light source and coat its surface with a layer of yellow phosphor. When the blue LED chip emits light, part of the blue light is emitted directly through the phosphor, while the other part of the blue light excites the phosphor to emit yellow light. When these two colors of light (blue light and yellow light) are mixed, the white light we see is produced.
D: White light is emitted by blue chip + red phosphor
- This option is incorrect. Although blue and red are one of the three primary colors of light, white light cannot be produced by the combination of blue chip and red phosphor alone. White light needs to contain a wider spectrum of components, not just blue and red.
In summary, the correct answer is C: White light is emitted by blue chip + yellow phosphor.