The intensity of sunlight impinging on Earth is about 1.4 kW/m².What is the power emitted by the Sun in the spectrum of frequencies? (Earth-Sun distance = 1.5 × 10⁸ km,Earth radius = 6.4 × 10³ km. )

Question

Quizplus · Accepted Answer

The power emitted by the Sun can be calculated using the formula:
Power = (Intensity at Earth's distance) × (Surface area of a sphere with Earth-Sun distance as radius)
Surface area of a sphere = 4πr^2, where r is the radius of the sphere.
Surface area of the sphere with Earth-Sun distance as radius = 4π(1.5 × 10^11 m)^2
= 2.83 × 10^23 m^2
Intensity at Earth's distance = 1.4 kW/m^2
Power emitted by the Sun = (1.4 kW/m^2) × (2.83 × 10^23 m^2)
= 3.96 × 10^26 W
= 4.0 × 10^26 W (rounded to two significant figures)
Therefore, the best choice is A, which is closest to 4.0 × 10^26 W.

The Intensity of Sunlight Impinging on Earth Is About 1