1) Consider the following questions a) Light takes 8 minutes and 19 seconds to r
ID: 939330 • Letter: 1
Question
1) Consider the following questions
a) Light takes 8 minutes and 19 seconds to reach from the sun to the earth. The speed of light is 3.0x10^8 m/s. How far (in meters) away is the earth from the sun?
b) Energy from the sun goes everywhere. What is the surface area of sphere with a radius of Earth’s orbit? (A=4 pi r²)
c) What is the surface area of your pupil in m²?
d) What is the ratio of the surface area of the sphere with a radius the size of Earth’s orbit to the surface area of your pupil?
e) If 1.2x10^34 J of energy are released by the sun in a year, how much of it enters your eye if you stare directly at the sun for 6 minutes?
Explanation / Answer
a)
We know speed = distance / time
We know the speed and time (in min).
Solution :
Conversion of time to second
Time conversion
8 min+19 second = 8 x 60 s + 19 s = 499 s
Distance = speed x time = 3.0E8 m/s x 499 s = 1.50 E 11 m
b) In order to calculate are of surface of earth we need the radius of earth.
Radius of earth is 6371000 m
Aread of earth = 3.14 x 4 x ( 3671000m)2 = 5.098 E14 m2
c) Surface area of pupil
radius of pupil is 2 mm and so area
= 4 x 3.14 x ( 2 E-3 m )2
= 5.024 E -5 m2
d)
Ratio of surface area of size of earth orbit to the surface area of pupil
= 5.098E14 m2/ 5.04E-5 m2
= 1.014 E19
e)
energy absorbed by eye = 1.2 E34 x (5.024 m2 /5.098E14 )x 6 x 60 s
= 4.26 E17 J
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