The photocell is one of the simplest and least expensive optical sensors. It can sense changes in light, but not color.
As you can see from the photocell schematic symbol here 
the light, represented by the arrows, is shining on to a resistor, the zigzag lines, and this changes the amount of resistance in the circuit.
What are some applications of optical technology in the designed world?
Not all optical devices use computer technology, such as the microscope, but advances in technology and digitial computers have developed new advances and applications of optical devices such as digital microscopes, lasers, fiber optics, optical telescopes, bar code readers and scanners. What other applications of optical and computer technology can you think of?
Explain science concepts and math concepts applied in optical technology such as light wave frequency, period, reflection, and refraction.
- What is light? How does it move?
- What different kinds of light are there?