1 ) The intensity of sunlight that reaches the Earth\'s atmosphere is about 1500

Question

1 ) The intensity of sunlight that reaches the Earth's atmosphere is about 1500 W/m2. What is the intensity of the sunlight that reaches Jupiter? Jupiter is 5.2 times as far from the sun as Earth. unit in w/m^2

2 ) Michelle is enjoying a picnic across the valley from a cliff. She is playing music on her radio (assume it to be an isotropic source) and notices an echo from the cliff. She claps her hands and the echo takes 2.0 s to return.
(a) Given that the speed of sound in air is 343 m/s on that day, how far away is the cliff? unit in m.

(b) If the intensity of the music 1.0 m from the radio is 1.0 10-5 W/m2, what is the intensity of the music arriving at the cliff? unit W/m2
W/m2

Explanation / Answer

1) The intensity of the sunlight reached the earth is Ie = 1500 W/m2 As the intensity of the sunlight is isotropic and varies incersly as the square of the radius of the planet (area = 4R2), Ij/Ie = Re2/Rj2 where Ij is the intensity on Jupiter Ie is the intensity on the earth Re is the radius of the earth Rj is the radius of the Jupiter Ij = Ie*Re2/(5.2Re)2 Ij = 1500 W/m2/27.04 Ij = 1500 W/m2/27.04 Ij = 55.47 W/m2 2) The speed of the sound is c = 343 m/s The time taken to hear the echo is t = 2 s The time taken by the sound to reac the hill is t1/2 = 1 s The distance of the hill is d = c*t1/2 = 343 m The intensity of the music at 1 m distance is I0 = 1*10-5 W/m2 The intensity of the music at the hill is I = I0 d02/d2 I = 1*10-5 W/m2 *1 m2/(343 m)2

I = 8.499*10-11 W/m2 The intensity of the music at the hill is I = I0 d02/d2 I = 1*10-5 W/m2 *1 m2/(343 m)2

I = 8.499*10-11 W/m2

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