The World Communicates - Questions. Help please!! (1 Viewer)

[zannasheayarrow]

Hey guys, can someone please help me with these questions. I don't want just an answer - I want to know how to go about solving them.

1) The intensity of solar energy from the sun arriving at the earth's surface is approximately 1 400 J m^-2, that is 1 400 joules fall on each square metre of the earth's surface per second. The sun lies 1.5 x 10^11m from the earth. The sun has a radius of 7.0 x 10^8 km. At what rate is the sun radiating energy (per m^2 of its surface)?

2) The intensity of light detected from a light source is I units when the detector is placed 1.0m from the source. If the detector is moved to 50cm from the source, what is the new intensity reading?

3) At a distance of 10m from a point source of sound energy, the intensity is 5x10^-2 W m^-2. What will the intensity be at 20m and 100m from the sound source?

Thanks! Also how do you study for a prac test????

 

[nightweaver066]

Intensity of light is inversely proportional to the distance.

If an object experiences 100J/m^2 at 1m distance, it would experience, 25J/m^2 at 2m distance.

 

[jnney]

for question 2 and 3 use the distance intensity formula in your textbook / notes and plug those in to find a value for one of the unknowns. it's simple.

 

[RivalryofTroll]

How to study for prac-test?

Learn how to write up a prac? Duh!
If you know what the prac is about beforehand, then do some background research.

Aim:

Hypothesis:

Equipment:

Risk Assessment:

Method:

Results:

Conclusion (discussion may be included):