However, it’s easy to solve this problem.
Let’s use digital camera and a remote controller for TV, DVD player or air conditioner.
The remote controller irradiates the infrared light to send the signals.
At first, when the switch is off, the infrared light is NOT observed.
Secondly, when the switch is ON, your eyes do NOT catch the light.
Thirdly, when the switch is ON, digital camera can detect the light, and you can observe it.
It's very interesting.
There is the invisible light in our world.
Hope you and your kids enjoy the exam
The remote controller irradiates the infrared light to send the signals.
At first, when the switch is off, the infrared light is NOT observed.
Secondly, when the switch is ON, your eyes do NOT catch the light.
Thirdly, when the switch is ON, digital camera can detect the light, and you can observe it.
It's very interesting.
There is the invisible light in our world.
Hope you and your kids enjoy the exam
