Suppose it were possible to lower a yellow sodium lamp toward the event horizon of a black hole. What would an observer see while watching from a safe distance?
A) The brightness and color would each remain unchanged.
B) The light from the lamp would change to orange and then red.
C) The light would remain yellow, but there would be fewer and fewer photons being emitted from it.
D) The light from the lamp would change to green and then blue.

Question

Quizplus · Accepted Answer

As the sodium lamp approaches the event horizon of a black hole, the gravitational field becomes stronger, causing the light emitted from the lamp to undergo gravitational redshift. This effect stretches the wavelength of the light, shifting its color from yellow towards the red end of the spectrum.

Suppose It Were Possible to Lower a Yellow Sodium Lamp