Time for light to reach earth homework

In summary: Jupiter is 318 times as massive as the Earth, so the number you're looking for should be a lot closer to 318 times the mass of the Earth. (It is a little more complicated than that, because Jupiter is a gas giant rather than a solid planet, but you should be able to get a reasonable approximation based on the Earth's mass and Jupiter's mass.)
  • #1
phys1120
2
0
QUESTION 1 (3 points):
a) Given that the Sun is 150,000,000 km from Earth, how long does it take
light to travel from the Earth to the Sun. Give your answer in minutes (min)

b) The Cassini spacecraft , currently in orbit about Saturn, sends its data to
Earth using radio waves. Assume that Saturn is at its closest approach to
Earth. How long does it take the signals to reach Earth from Saturn? Give
your answer it minutes (min).

QUESTION 2 (3 points):
A regular incandescent light bulb radiates most strongly at a wavelength of
3000 nm.
a) How hot is the filament? Give your answer in Kelvins (K)

b) In which part of the spectrum does it emit the most radiation: visible, or
infrared (heat)?

QUESTION 3 (6 points):
Use the orbit of Ganymede to calculate the mass of Jupiter in kilograms. You
will need to use the size of the orbit and orbital period, which can be found in
Table 8.1 on page 216 of the 6th edition of the text. (Any other text boox will
have a table of appendix with this information. Remember that the units to
calculate the mass have to be in metres, and seconds if you want to get the
mass in kilograms.
 
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  • #2
Generally, we expect people who want help with homework to list all relevant equations and show their attempt at all questions. Please do this and we'll help you.

BTW, this should really go in the "Homework and Coursework" section.
 
  • #3
#1a) time = distance
speed
time = 150,000,000
299,792.458m/s
time = 150,000,000
482,469,193.528km/s
time = 0.3109km/s
time = 18.654km/m
b) NO IDEA!

#2a) wavelength = 1
temperature
3000nm = 2.9 x10^6
temperature
3000nm = 2,900,000
temperature
temperature = 966.667
b)infrared

#3) M = 4pie^2a^3
GP^2
M = 39.478 x 1634.206m^3
6.7 7.15^2
M = 5.892 x 2,417,217.876
51.123
M = 5.892 x 47,285.17
M = 278,604.222
 
  • #4
I think there was a problem that messed up your formatting and deleted some of your text, but I'll help the best I can.

phys1120 said:
#1a) time = distance
speed
time = 150,000,000
299,792.458m/s
time = 150,000,000
482,469,193.528km/s
time = 0.3109km/s
time = 18.654km/m
b) NO IDEA!

For 1a), all you need to know is that time equals distance divided by speed. This should be obvious; if you're driving at 40 km/h, you'd take one hour to cover 40 km, 2 hours to cover 80 km, and so on. The speed of light is 299 792.458 km/s (not m/s) and the distance from the Sun to the Earth is 150 000 000 km. So how many seconds does it take sunlight to reach earth?

For 1b), try looking at the back of your textbook for the orbital parameters of Saturn and Earth. How far is Saturn from Earth at closest approach?

#2a) wavelength = 1
temperature
3000nm = 2.9 x10^6
temperature
3000nm = 2,900,000
temperature
temperature = 966.667
b)infrared

All of this is correct.
#3) M = 4pie^2a^3
GP^2
M = 39.478 x 1634.206m^3
6.7 7.15^2
M = 5.892 x 2,417,217.876
51.123
M = 5.892 x 47,285.17
M = 278,604.222

I can't follow this, but 278 604 kg can't possibly be right. That's 278 tons, about the weight of a Boeing 747, but Jupiter is a planet much more massive (by far) than the Earth.
 

1. How long does it take for light to reach Earth?

It takes about 8 minutes and 20 seconds for light from the Sun to reach Earth. However, the time it takes for light to reach Earth varies for other sources, as some stars and galaxies are much further away.

2. Why does it take time for light to reach Earth?

Light travels at a speed of approximately 186,282 miles per second, but even at this incredible speed, it takes time for light to travel through the vast distances of space. The distance between the Sun and Earth is about 93 million miles, which is why it takes 8 minutes and 20 seconds for light to reach us.

3. How do scientists measure the time it takes for light to reach Earth?

Scientists use a unit of measurement called a light-year to measure the distance that light travels in one year. One light-year is approximately 5.88 trillion miles. By knowing the distance between Earth and a source of light, scientists can calculate the time it takes for light to reach us.

4. Does light always travel at the same speed?

Yes, the speed of light is a constant and is considered the fastest speed possible in the universe. It is a fundamental constant in physics and is denoted by the letter "c". However, the speed of light can be affected by the medium it is traveling through, such as air, water, or glass.

5. Can light travel instantaneously?

No, according to the laws of physics, nothing can travel faster than the speed of light. This means that even if we were to discover a way to travel at the speed of light, it would still take 8 minutes and 20 seconds for light from the Sun to reach Earth.

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