Mike fattori, a 64 year old male from Toronto asks on September 20, 2015,
When my smartphone is off, its screen is black. In the bright sun the black screen absorbs a lot of sunlight and gets very hot. If the phone was on - displaying a blank white screen - would the screen absorb less solar radiation because it's white?
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Short answer: only a tiny bit less.
Both scientists noted that having the screen on would use energy from the smartphone's battery and that would generate heat, but the questioner was only interested in the effect of sunlight.
In the end Lorne Whitehead, physics professor at UBC and expert on light reflection answered, "Jess is right, it makes a difference whether it is an OLED (Organic Light-Emitting Diode) screen, whose reflectance is independent of screen state, or an LCD (Liquid Crystal Display), for which there is a dependence. However, it's a tiny difference, because the color screens have very low transmission due to the RGB (Red, Green, Blue) color filter array. So overall, no matter what, the screen absorbs almost all of the ambient light that strikes it. By the way this is good for contrast, because otherwise the screen colors would be diluted by the reflected light. From the perspective of ambient light, a cell phone screen is very close to black.”
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