Many modern cars use high brightness LEDs for their rear lights. They tend to be rapidly switched on and off for 'normal intensity' and fully on for 'high intensity' when the brakes are also applied. When driving behind these cars I find the LED lights very distracting - whenever I move my eyes from one spot to another the lights appear to leave a trail of very bright dots caused by their rapid switching. Normal incandescent bulbs do not look like this, nor do the LED car lights when they at full intensity. Domestic items with LED displays also tend to do the same thing (I noticed it on a washing machine today). I also see it to a lesser extent with fluorescent lights.

My daughter also sees the flickering car lights when moving her eyes, but my son does not, and neither do other people I've asked. I understand why LEDs are rapidly switched in this way, and why they appear as a string of dots when I move my eyes - my question is why do some people apparently not see the effect? Is our perception somehow different? I have read reports that the brain 'switches off' visual processing when the eyes are flicked from one point to another - could this 'switching off' vary from one person to another?

I had a telephone a few years ago with a red LED that would flash when I had messages. I noticed on several occassions the LED would appear to be flashing through the corner of my eye, but when I turned to look at it the flashing would immediately stop. As soon as I would look away the flashing would again begin. Also there were no messages on the phone to cause the flashing.

The remote control contains an infra-red LED which emits a coded pulse train in a single wavelength to a spectrally matched receiver.  Since LEDs are available at wavelengths throughout the visible spectrum, and into the ultra-violet, why is infra-red used exclusively for remote control?  I remember once having a TV that had an ultrasonic control so it's clearly not the wavelength that's important, and it would be useful if the controller emitted, say, yellow light as you could see it was working.....