From d1c77c2208adcee33a6e5c0afa710cde6fccd09b Mon Sep 17 00:00:00 2001 From: eggy Date: Tue, 30 Mar 2021 17:07:17 -0400 Subject: [PATCH] phys: give reason why you divide by 4 --- docs/sph4u7.md | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/docs/sph4u7.md b/docs/sph4u7.md index 706e894..d1f2e2e 100644 --- a/docs/sph4u7.md +++ b/docs/sph4u7.md @@ -472,8 +472,8 @@ $$I=\frac{P}{4\pi d^2}$$ **Albedo** ($\alpha$) is the ratio of power from incident rays reflected or scattered to the power absorbed by a body, ranging from 0 to 1. A black body has albedo 0. On average, Earth's albedo is equal to $0.3$ due primarily to the atmosphere but also clouds and ice. $$\alpha=\frac{\text{energy scattered/reflected}}{\text{energy absorbed}}$$ -As Earth is not a flat disk pointed at the sun, in reality the sun's intensity is reduced arbitrarily to a quarter. Therefore, the power absorbed/incident to the Earth is equal to, where $S$ is the solar constant: -$$P_\text{in}=(1-\alpha)\frac{1}{4}SA$$ +As Earth is not a flat disk pointed at the sun, in reality the sun's intensity is reduced to a quarter due to the formula for a sphere. Therefore, the power absorbed/incident to the Earth is equal to, where $S$ is the solar constant: +$$P_\text{in}=(1-\alpha)\frac{S}{4}A$$ Greenhouse gases are responsible for remaining increases in temperature.