Lord Jubjub

2009-Dec-17, 12:49 AM

Thought experiment:

A semi-trailer truck is painted black such that no light is reflected or emitted except through the headlights, running lights and tail lights. These all emit at exactly 510 nanometers (greenish light).

You are sitting by the side of the road with a device that will tell you, to the nearest nanometer, the wavelength of light it detects. As the truck approaches you, the light will appear bluer. You read exactly 510 nm as the truck passes you. The truck then drives away from you with a redder light.

If the truck was driving, relative to you, at 60 mph (100 kmph), would the wavelength differences be detectable?

A semi-trailer truck is painted black such that no light is reflected or emitted except through the headlights, running lights and tail lights. These all emit at exactly 510 nanometers (greenish light).

You are sitting by the side of the road with a device that will tell you, to the nearest nanometer, the wavelength of light it detects. As the truck approaches you, the light will appear bluer. You read exactly 510 nm as the truck passes you. The truck then drives away from you with a redder light.

If the truck was driving, relative to you, at 60 mph (100 kmph), would the wavelength differences be detectable?