Physics, 24.10.2019 23:43 iBrain

Earth is about 150 million kilometers from the sun, and the apparent brightness of the sun in our sky is about 1300 watts/m2. using these two facts and the inverse square law for light, determine the apparent brightness that we would measure for the sun if we were located at the following positions.

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Answer from: papabosue

The question is incomplete. Here is the complete one.

Earth is about 150 million kilometers from the Sun and the apparent brightness of the Sun in our sky is about 1300 watts/m². Using these two facts and the inverse square law for light, determine the apparent brightness that we would measure for the Sun if we were located at the following positions: A) Half Earth's distance from the Sun; B) Twice Earth's distance form the Sun; C) 7 times Earth's distance from the Sun;

A) 5200 W/m²; B) 352 W/m²; C) 26.53 W/m²;

Explanation: A point source that spreads its influence in all directions follows the Inverse Square Law. It states the intensity of the source at any given radius r is the source's strength divided by the area of a sphere. It basically shows that if the radius r doubles, the intensity I is 1/4 of the intensity. So,

A) The apparent brightness of the Sun is 1300W/m² and Earth is 150 million km from the Sun. To find the brightness at half Earth's distance, we have to compare each other, which mean:

$\frac{I_{T} }{I_{1/2} } = (\frac{r_{2} }{r_{1} })^{2}$

$I_{1/2} = I_{T} . (\frac{r_{1} }{r_{2} }) ^{2}$

$I_{1/2} = 1300. (\frac{150}{\frac{150}{2} }) ^{2}$

$I_{1/2} = 1300.2^{2}$

$I_{1/2}$ = 5200 W/m²

B) For twice the Earth's distance:

$I_{2} = I_{T} . (\frac{r_{1} }{r_{2} }) ^{2}$

$I_{2} = 1300 . (\frac{150 }{300 }) ^{2}$

$I_{2} = 1300 . 0.5 ^{2}$

$I_{2} =$ 325 W/m²

C) For 7 times the Earth's distance:

$I_{7} = I_{T} . (\frac{r_{1} }{r_{2} }) ^{2}$

$I_{7} = 1300 . (\frac{150}{7.150}) ^{2}$

$I_{7} = 1300 . (\frac{1}{7} ) ^{2}$

$I_{7} =$ 26.53 W/m²

Answer from: Quest

Cis the

Answer from: Quest

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

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