There is an inverse relationship between distance and light intensity – as the distance increases,
light intensity decreases
. … The light energy at three times the distance away is spread over nine times the area, and so on.
Why does luminosity decrease with distance?
Notice that as the distance increases, the light must spread out over a larger surface and the surface brightness decreases in accordance with a “one over r squared” relationship. The decrease goes as r squared
because the area over which the light is spread is proportional to the distance squared
.
Does luminosity decrease with distance?
The difference between luminosity and
apparent brightness
How does luminosity calculate distance?
- The luminosity of the lightbulb is L = 100 W.
- The brightness is b = 0.1 W/m
2
. - So the distance is given by d
2
= (100 W)/(4 Pi x 0.1 W/m
2
). - Since 4 Pi is approximately 10, this is d
2
= (100 / 1) m
2
. - Thus d
2
= 100 m
2
. - We now know what d
2
is. … - So d = 10 m.
The apparent brightness
What life would be like without light?
Without sunlight, it would be bleak on earth. There wouldn’t be any plants, animals and people. There
would be no other form of life
. No fossil energy sources such as coal, oil and natural gas would be available to generate energy.
How does the distance between a light source?
Every light source is different, but the intensity changes in the same way. The intensity of light is inversely proportional to the square of the distance. This means that as the distance from a light source increases,
the intensity of light is equal to a value multiplied by 1/d
2
,.
Is luminosity a distance?
Luminosity is
an intrinsic quantity that does not depend on distance
. The apparent brightness
What is the relationship between luminosity and distance?
At a particular Luminosity, the more distant an object is,
the fainter its apparent brightness
How is luminosity calculated?
” The Luminosity of a star
is proportional to its Effective Temperature to the 4
th
power and its Radius squared
.” Example 1: Two stars are the same size, (R
A
=R
B
), but star A is 2x hotter than star B (T
A
=2T
B
): Therefore: Star A is 2
4
or 16x brighter than Star B.
What is the color of the hottest star?
White stars are hotter than red and yellow.
Blue stars
are the hottest stars of all.
What is the hottest type of star in the universe?
The hottest one measures ~210,000 K; the hottest known star.
The Wolf-Rayet star WR 102
is the hottest star known, at 210,000 K.
Which star has the greatest luminosity?
Which star has the greatest luminosity?
Antares
has the greatest luminosity because its absolute magnitude is the smallest.
What will happen if there will be no light?
It flows as radiation from the surface into space, warms our planet and sets in motion many chemical and physical processes. Without sunlight, it would be
bleak on earth
. There wouldn’t be any plants, animals and people. There would be no other form of life…..
Can humans survive without light?
A study published in the Archives of Internal Medicine, stated that humans need sunlight for vitamin D. … Submariners have gone without sunlight for periods exceeding 6-months, using vitamin D supplements. It is
unlikely
, though, that an adult could die directly and exclusively from prolonged darkness.
What would happen if the moon broke apart?
If the moon exploded,
the night sky would change
. We would see more stars in the sky, but we would also see more meteors and experience more meteorites. The position of the Earth in space would change and temperatures and seasons would dramatically alter, and our ocean tides would be much weaker.
